Search

The intricate system of connections between the eye and the brain implies that there are common pathways for the eye and brain that get activated following injury. Hypoxia-ischemia (HI) related encephalopathy is a consequence of brain injury caused by oxygen and blood flow deprivation that may result in visual disturbances and neurodevelopmental disorders in surviving neonates. We have previously shown that the tyrosine receptor kinase B (TrkB) agonist/modulator improves neuronal survival and long-term neuroprotection in a sexually differential way. In this study, we tested the hypotheses that; 1) TrkB agonist therapy improves the visual function in a sexually differential way; 2) Visual function detected by electroretinogram (ERG) correlates with severity of brain injury detected by magnetic resonance (MRI) imaging following neonatal HI in mice. To test our hypotheses, we used C57/BL6 mice at postnatal day (P) 9 and subjected them to either Vannucci's rodent model of neonatal HI or sham surgery. ERG was performed at P 30, 60, and 90. MRI was performed following the completion of the ERG. ERG in these mice showed that the a-wave is normal, but the b-wave amplitude is severely abnormal, reducing the b/a wave amplitude ratio. Inner retina function was found to be perturbed as we detected severely attenuated oscillatory potential after HI. No sex differences were detected in the injury and severity pattern to the retina as well as in response to 7,8-DHF therapy. Strong correlations were detected between the percent change in b/a ratio and percent hemispheric/hippocampal tissue loss obtained by MRI, suggesting that ERG is a valuable noninvasive tool that can predict the long-term severity of brain injury.

The rapid development of gene therapy and genome editing techniques brings up an urgent need to develop safe and efficient nanoplatforms for nucleic acids and CRISPR genome editors. Herein we report a stimulus-responsive silica nanoparticle (SNP) capable of encapsulating biomacromolecules in their active forms with a high loading content and loading efficiency as well as a well-controlled nanoparticle size (~50 nm). A disulfide crosslinker was integrated into the silica network, endowing SNP with glutathione (GSH)-responsive cargo release capability when internalized by target cells. An imidazole-containing component was incorporated into the SNP to enhance the endosomal escape capability. The SNP can deliver various cargos, including nucleic acids (e.g., DNA and mRNA) and CRISPR genome editors (e.g., Cas9/sgRNA ribonucleoprotein (RNP), and RNP with donor DNA) with excellent efficiency and biocompatibility. The SNP surface can be PEGylated and functionalized with different targeting ligands. In vivo studies showed that subretinally injected SNP conjugated with all-trans-retinoic acid (ATRA) and intravenously injected SNP conjugated with GalNAc can effectively deliver mRNA and RNP to murine retinal pigment epithelium (RPE) cells and liver cells, respectively, leading to efficient genome editing. Overall, the SNP is a promising nanoplatform for various applications including gene therapy and genome editing.

Leber Congenital Amaurosis (LCA16) is a progressive vision loss disorder caused by point mutations in the KCNJ13 gene, which encodes an inward-rectifying potassium channel, Kir7.1. A nonsense mutation, W53X (c.158G>A), leads to premature truncation of the protein, which disrupts K+ conductance and makes retinal pigmented epithelium (RPE) non-functional. While there are no current treatments for LCA16, here we explore CRISPR base editing as a strategy to correct the single base pair pathogenic variant. We show that silica nanoparticle (SNC)-mediated delivery of an adenine base editor (ABE8e) mRNA and single-guide RNA can precisely and efficiently correct the KCNJ13W53X mutation to restore Kir7.1 channel function in an induced pluripotent stem cell-derived RPE (iPSC-RPE) model of LCA16, as well as in patient-derived fibroblasts and in a new LCA16 mouse model. We observed a higher editing efficiency in LCA16 patient-derived fibroblasts (47.38% ± 1.02) than in iPSC-RPE (16.90% ± 1.58) with no detectable off-target editing. The restored channel function in the edited cells resulted in a phenotype comparable to wild-type cells, suggesting the possibility that this treatment could restore vision in LCA16 patients. Injection of ABE8e-carrying SNCs decorated with all-trans retinoic acid (ATRA) ligand into the subretinal space in LCA16 mice showed specific delivery only to RPE and resulted in gene correction in approximately 10% of RPE cells that received the editing machinery. We observed marginal recovery of electroretinogram (ERG) following correction of the W53X allele at the injection site with no further degeneration of RPE. These findings provide a foundation and a proof-of-concept to transition from bench to bedside and support its further development for treating pediatric blindness using a safer mode of SNC-mediated delivery of base editors.

Inward-rectifier potassium channel 7.1 (Kir7.1) is present in the polarized epithelium, including the retinal pigmented epithelium. A single amino acid change at position 153 in the KCNJ13 gene, a substitution of threonine to isoleucine in the Kir7.1 protein, causes blindness. We hypothesized that the disease caused by this single amino acid substitution within the transmembrane protein domain could alter the translation, localization, or ion transport properties. We assessed the effects of amino acid side-chain length, arrangement, and polarity on channel structure and function. We showed that the T153I mutation yielded a full-length protein localized to the cell membrane. Whole cell patch-clamp recordings and chord conductance analyses revealed that the T153I mutant channel had negligible K+ conductance and failed to hyperpolarize the membrane potential. However, the mutant channel exhibited enhanced inward current when rubidium was used as a charge carrier, suggesting that an inner pore had formed and the channel was dysfunctional. Substituting with a polar, nonpolar, or short side-chain amino acid did not affect the localization of the protein. Still, it had an altered channel function due to differences in pore radius. Polar side chains (cysteine and serine) with inner pore radii comparable to wildtype exhibited normal inward K+ conductance. Short side chains (glycine and alanine) produced a channel with wider than expected inner pore size and lacked the biophysical characteristics of the wild-type channel. Leucine substitution produced results similar to the T153I mutant channel. This study provides direct electrophysiological evidence for the structure and function of the Kir7.1 channel’s narrow inner pore in regulating conductance.

Efficient delivery of hydrophilic drugs, nucleic acids, proteins, and any combination thereof is essential for various biomedical applications. Herein, we report a straightforward, yet versatile approach to efficiently encapsulate and deliver various hydrophilic payloads using a pH-responsive silica–metal–organic framework hybrid nanoparticle (SMOF NP) consisting of both silica and zeolitic imidazole framework (ZIF). This unique SMOF NP offers a high loading content and efficiency, excellent stability, and robust intracellular delivery of a variety of payloads, including hydrophilic small molecule drugs (e.g., doxorubicin hydrochloride), nucleic acids (e.g., DNA and mRNA), and genome-editing machineries (e.g., Cas9-sgRNA ribonucleoprotein (RNP), and RNP together with donor DNA (e.g., RNP + ssODN)). The superior drug delivery/gene transfection/genome-editing efficiencies of the SMOF NP are attributed to its pH-controlled release and endosomal escape capabilities due to the proton sponge effect enabled by the imidazole moieties in the SMOF NPs. Moreover, the surface of the SMOF NP can be easily customized (e.g., PEGylation and ligand conjugation) via various functional groups incorporated into the silica component. RNP-loaded SMOF NPs induced efficient genome editing in vivo in murine retinal pigment epithelium (RPE) tissue via subretinal injection, providing a highly promising nanoplatform for the delivery of a wide range of hydrophilic payloads.

Dominantly inherited disorders are not typically considered to be therapeutic candidates for gene augmentation. Here, we utilized induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) to test the potential of gene augmentation to treat Best disease, a dominant macular dystrophy caused by over 200 missense mutations in BEST1. Gene augmentation in iPSC-RPE fully restored BEST1 calcium-activated chloride channel activity and improved rhodopsin degradation in an iPSC-RPE model of recessive bestrophinopathy as well as in two models of dominant Best disease caused by different mutations in regions encoding ion-binding domains. A third dominant Best disease iPSC-RPE model did not respond to gene augmentation, but showed normalization of BEST1 channel activity following CRISPR-Cas9 editing of the mutant allele. We then subjected all three dominant Best disease iPSC-RPE models to gene editing, which produced premature stop codons specifically within the mutant BEST1 alleles. Single-cell profiling demonstrated no adverse perturbation of retinal pigment epithelium (RPE) transcriptional programs in any model, although off-target analysis detected a silent genomic alteration in one model. These results suggest that gene augmentation is a viable first-line approach for some individuals with dominant Best disease and that non-responders are candidates for alternate approaches such as gene editing. However, testing gene editing strategies for on-target efficiency and off-target events using personalized iPSC-RPE model systems is warranted. In summary, personalized iPSC-RPE models can be used to select among a growing list of gene therapy options to maximize safety and efficacy while minimizing time and cost. Similar scenarios likely exist for other genotypically diverse channelopathies, expanding the therapeutic landscape for affected individuals.

Purpose: We constructed and characterized knockout and conditional knockout mice for KCNJ13, encoding the inwardly rectifying K+ channel of the Kir superfamily Kir7.1, mutations in which cause both Snowflake Vitreoretinal Degeneration (SVD) and Retinitis pigmentosa (RP) to further elucidate the pathology of this disease and to develop a potential model system for gene therapy trials.Methods: A Kcnj13 knockout mouse line was constructed by inserting a gene trap cassette expressing beta-galactosidase flanked by FRT sites in intron 1 with LoxP sites flanking exon two and converted to a conditional knockout by FLP recombination followed by crossing with C57BL/6J mice having Cre driven by the VMD2 promoter. Lentiviral replacement of Kcnj13 was driven by the EF1a or VMD2 promoters.Results: Blue-Gal expression is evident in E12.5 brain ventricular choroid plexus, lens, neural retina layer, and anterior RPE. In the adult eye expression is seen in the ciliary body, RPE and choroid. Adult conditional Kcnj13 ko mice show loss of photoreceptors in the outer nuclear layer, inner nuclear layer thinning with loss of bipolar cells, and thinning and disruption of the outer plexiform layer, correlating with Cre expression in the overlying RPE which, although preserved, shows morphological disruption. Fundoscopy and OCT show signs of retinal degeneration consistent with the histology, and photopic and scotopic ERGs are decreased in amplitude or extinguished. Lentiviral based replacement of Kcnj13 resulted in increased ERG c- but not a- or b- wave amplitudes.Conclusion: Ocular KCNJ13 expression starts in the choroid, lens, ciliary body, and anterior retina, while later expression centers on the RPE with no/lower expression in the neuroretina. Although KCNJ13 expression is not required for survival of the RPE, it is necessary for RPE maintenance of the photoreceptors, and loss of the photoreceptor, outer plexiform, and outer nuclear layers occur in adult KCNJ13 cKO mice, concomitant with decreased amplitude and eventual extinguishing of the ERG and signs of retinitis pigmentosa on fundoscopy and OCT. Kcnj13 replacement resulting in recovery of the ERG c- but not a- and b-waves is consistent with the degree of photoreceptor degeneration seen on histology.

Aging is a significant factor in the development of age-related diseases but how aging disrupts cellular homeostasis to cause age-related retinal disease is unknown. Here, we further our studies on transmembrane protein 135 (Tmem135), a gene involved in retinal aging, by examining the transcriptomic profiles of wild-type, heterozygous and homozygous Tmem135 mutant posterior eyecup samples through RNA sequencing (RNA-Seq). We found significant gene expression changes in both heterozygous and homozygous Tmem135 mutant mouse eyecups that correlate with visual function deficits. Further analysis revealed that expression of many genes involved in lipid metabolism are changed due to the Tmem135 mutation. Consistent with these changes, we found increased lipid accumulation in mutant Tmem135 eyecup samples. Since mutant Tmem135 mice have similar ocular pathologies as human age-related macular degeneration (AMD) eyes, we compared our homozygous Tmem135 mutant eyecup RNA-Seq dataset with transcriptomic datasets of human AMD donor eyes. We found similar changes in genes involved in lipid metabolism between the homozygous Tmem135 mutant eyecups and AMD donor eyes. Our study suggests that the Tmem135 mutation affects lipid metabolism as similarly observed in human AMD eyes, thus Tmem135 mutant mice can serve as a good model for the role of dysregulated lipid metabolism in AMD.

Delivery technologies for the CRISPR-Cas9 (CRISPR, clustered regularly interspaced short palindromic repeats) gene editing system often require viral vectors, which pose safety concerns for therapeutic genome editing1. Alternatively, cationic liposomal components or polymers can be used to encapsulate multiple CRISPR components into large particles (typically >100 nm diameter); however, such systems are limited by variability in the loading of the cargo. Here, we report the design of customizable synthetic nanoparticles for the delivery of Cas9 nuclease and a single-guide RNA (sgRNA) that enables the controlled stoichiometry of CRISPR components and limits the possible safety concerns in vivo. We describe the synthesis of a thin glutathione (GSH)-cleavable covalently crosslinked polymer coating, called a nanocapsule (NC), around a preassembled ribonucleoprotein (RNP) complex between a Cas9 nuclease and an sgRNA. The NC is synthesized by in situ polymerization, has a hydrodynamic diameter of 25 nm and can be customized via facile surface modification. NCs efficiently generate targeted gene edits in vitro without any apparent cytotoxicity. Furthermore, NCs produce robust gene editing in vivo in murine retinal pigment epithelium (RPE) tissue and skeletal muscle after local administration. This customizable NC nanoplatform efficiently delivers CRISPR RNP complexes for in vitro and in vivo somatic gene editing. Polymer nanocapsules, assembled around a ribonucleoprotein complex of Cas9 nuclease and a single-guide RNA, enable safe and efficient gene editing in vitro and in vivo.

Ischemic stroke is a major cause of long-term disabilities, including vision loss. Neuronal and blood vessel maturation can affect the susceptibility of and outcome after ischemic stroke. Although we recently reported that exposure of neonatal mice to hypoxia–ischemia (HI) severely compromises the integrity of the retinal neurovasculature, it is not known whether juvenile mice are similarly impacted. Here we examined the effect of HI injury in juvenile mice on retinal structure and function, in particular the susceptibility of retinal neurons and blood vessels to HI damage. Our studies demonstrated that the retina suffered from functional and structural injuries, including reduced b-wave, thinning of the inner retinal layers, macroglial remodeling, and deterioration of the vasculature. The degeneration of the retinal vasculature associated with HI resulted in a significant decrease in the numbers of pericytes and endothelial cells as well as an increase in capillary loss. Taken together, these findings suggest a need for juveniles suffering from ischemic stroke to be monitored for changes in retinal functional and structural integrity. Thus, there is an emergent need for developing therapeutic approaches to prevent and reverse retinal neurovascular dysfunction with exposure to ischemic stroke.

Purpose Aging is a critical risk factor for the development of retinal diseases, but how aging perturbs ocular homeostasis and contributes to disease is unknown. We identified transmembrane protein 135 (Tmem135) as a gene important for regulating retinal aging and mitochondrial dynamics in mice. Overexpression of Tmem135 causes mitochondrial fragmentation and pathologies in the hearts of mice. In this study, we examine the eyes of mice overexpressing wild-type Tmem135 (Tmem135 TG) and compare their phenotype to Tmem135 mutant mice. Methods Eyes were collected for histology, immunohistochemistry, electron microscopy, quantitative PCR, and Western blot analysis. Before tissue collection, electroretinography (ERG) was performed to assess visual function. Mouse retinal pigmented epithelium (RPE) cultures were established to visualize mitochondria. Results Pathologies were observed only in the RPE of Tmem135 TG mice, including degeneration, migratory cells, vacuolization, dysmorphogenesis, cell enlargement, and basal laminar deposit formation despite similar augmented levels of Tmem135 in the eyecup (RPE/choroid/sclera) and neural retina. We observed reduced mitochondria number and size in the Tmem135 TG RPE. ERG amplitudes were decreased in 365-day-old mice overexpressing Tmem135 that correlated with reduced expression of RPE cell markers. In Tmem135 mutant mice, RPE cells are thicker, smaller, and denser than their littermate controls without any signs of degeneration. Conclusions Overexpression and mutation of Tmem135 cause contrasting RPE abnormalities in mice that correlate with changes in mitochondrial shape and size (overfragmented in TG vs. overfused in mutant). We conclude proper regulation of mitochondrial homeostasis by TMEM135 is critical for RPE health.

Background Retinitis pigmentosa (RP) is the most common inherited retinal degenerative disease yet with no effective treatment available. The sigma-1 receptor (S1R), a ligand-regulated chaperone, emerges as a potential retina-protective therapeutic target. In particular, pharmacological activation of S1R was recently shown to rescue cones in the rd10 mouse, a rod Pde6b mutant that recapitulates the RP pathology of autonomous rod degeneration followed by secondary death of cones. The mechanisms underlying the S1R protection for cones are not understood in detail. Methods By rearing rd10/S1R−/− and rd10/S1R+/+ mice in dim light to decelerate rapid rod/cone degeneration, we were able to compare their retinal biochemistry, histology and functions throughout postnatal 3–6 weeks (3 W–6 W). Results The receptor-interacting protein kinases (RIP1/RIP3) and their interaction (proximity ligation) dramatically up-regulated after 5 W in rd10/S1R−/− (versus rd10/S1R+/+) retinas, indicative of intensified necroptosis activation, which was accompanied by exacerbated loss of cones. Greater rod loss in rd10/S1R−/− versus rd10/S1R+/+ retinas was evidenced by more cleaved Caspase3 (4 W) and lower rod electro-retinographic a-waves (4 W–6 W), concomitant with reduced LC3-II and CHOP (4 W–6 W), markers of autophagy and endoplasmic reticulum stress response, respectively. However, the opposite occurred at 3 W. Conclusion This study reveals previously uncharacterized S1R-associated mechanisms during rd10 photoreceptor degeneration, including S1R’s influences on necroptosis and autophagy as well as its biphasic role in rod degeneration upstream of cone death. Electronic supplementary material The online version of this article (doi:10.1186/s13024-017-0202-z) contains supplementary material, which is available to authorized users.

The KCNJ13 gene encodes the inwardly rectifying potassium channel, Kir7.1. Mutations in this gene cause childhood blindness, in which the a- and b-wave responses of electroretinogram (ERG) are abolished. The ERG a-wave is the light-induced hyperpolarization of retinal photoreceptors, and the b-wave is the depolarization of ON-bipolar cells. The Kir7.1 channel is localized to the apical aspects of retinal pigment epithelium (RPE) cells and contributes to a delayed c-wave response. We sought to understand why a defect in an RPE ion-channel result in abnormal electrophysiology at the level of the retinal neurons. We have established the expression of Kir7.1 channels in the mouse RPE. ERGs recorded after mice Kir7.1 suppression by shRNA, or by blocking with VU590, showed reduced a-, b- and c-wave amplitudes. In contrast, the Kir7.1 blocker had no effect on the ex-vivo isolated mouse retina ERG where the RPE is not attached to the isolated retina preparation. Finally, we confirmed the specificity of VU590 action by inhibition of native mouse RPE Kir7.1 current in patch-clamp experiment. We propose that mutant RPE Kir7.1 channels contribute directly to the abnormal ERG associated with blindness via alterations in sub-retinal space K+ homeostasis in the vicinity of the photoreceptor outer segment.

Dominantly inherited disorders are not typically considered therapeutic candidates for gene augmentation. Here, we utilized patient-specific induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) to test the potential of gene augmentation to treat Best disease, a dominant macular dystrophy caused by over 200 missense mutations in BEST1. Gene augmentation in iPSC-RPE fully restored BEST1 calcium-activated chloride channel activity and improved rhodopsin degradation in iPSC-RPE models of recessive bestrophinopathy and dominant Best disease caused by two different ion binding domain mutations. A dominant Best disease iPSC-RPE model that did not respond to gene augmentation showed normalization of BEST1 channel activity following CRISPR-Cas9 editing of the mutant allele. We then tested gene editing in all three dominant Best disease iPSC-RPE models, which produced premature stop codons exclusively within the mutant BEST1 alleles. Single-cell profiling demonstrated no adverse perturbation of RPE transcriptional programs in any model, although off-target analysis detected a silent genomic alteration in one model. These results suggest that gene augmentation is a viable first-line approach for some dominant Best disease patients and that non-responders are candidates for alternate approaches such as genome editing. However, testing genome editing strategies for on-target efficiency and off-target events using patient-matched iPSC-RPE model systems is warranted. In summary, personalized iPSC-RPE models can be used to select among a growing list of gene therapy options to maximize safety and efficacy while minimizing time and cost. Similar scenarios likely exist for other genotypically diverse channelopathies, expanding the therapeutic landscape for affected patients.SignificanceDominantly inherited disorders pose distinct challenges for gene therapies, particularly in the face of extreme mutational diversity. We tested whether a broad gene replacement strategy could reverse the cellular phenotype of Best disease, a dominant blinding condition that targets retinal pigment epithelium (RPE). Using RPE generated from patient-specific induced pluripotent stem cells (iPSCs), we show that gene replacement functionally overcomes some, but not all, of the tested mutations. In comparison, all dominant Best disease models tested were phenotypically corrected after mutation-specific genome editing, although one off-target genomic alteration was discovered. Our results support a two-tiered approach to gene therapy for Best disease, guided by safety and efficacy testing in iPSC-RPE models to maximize personal and public health value.

Dominantly inherited disorders are not typically considered therapeutic candidates for gene augmentation (GA). We tested whether GA or genome editing (GE) could serve as a solo therapy for autosomal dominant Best disease (adBD), a macular dystrophy linked to over 100 mutations in the BEST1 gene, which encodes a homo-pentameric calcium-activated chloride channel (CaCC) in the retinal pigment epithelium (RPE). Since no suitable animal models of adBD exist, we generated RPE from patient-derived induced pluripotent stem cells (iPSC-RPE) and found that GA restored CaCC activity and improved rhodopsin degradation in a subset of adBD lines. iPSC-RPE harboring adBD mutations in calcium clasp or chloride binding domains of the channel, but not in a putative structural region, were responsive to GA. However, reversal of the iPSC-RPE CaCC deficit was demonstrated in every adBD line following targeted CRISPR-Cas9 GE of the mutant allele. Importantly, 95% of GE events resulted in premature stop codons within the mutant allele, and single cell profiling demonstrated no adverse perturbation of RPE transcriptional programs post-editing. These results show that GA is a viable approach for a subset of adBD patients depending on the functional role of the mutated residue. Further, GA non-responders are candidates for targeted GE of the mutant allele. Similar scenarios likely exist for other genotypically diverse dominant diseases, expanding the therapeutic landscape for affected patients.

PurposeMutations in the KCNJ13 gene are known to cause Leber’s Congenital Amaurosis (LCA16), an inherited pediatric blindness. KCNJ13 gene encodes the Kir7.1 subunit protein which acts as a tetrameric inwardly rectifying potassium ion channel in the retinal pigment epithelium to maintain ionic homeostasis thereby allowing photoreceptors to encode visual information. We sought to determine if genetic approaches might be effective in treating blindness due to mutations in KCNJ13.MethodsWe developed patient-derived hiPSC-RPE carrying an autosomal recessive nonsense mutation in the KCNJ13 gene (c.158G>A, p.Trp53*). We performed biochemical and electrophysiology assays of Kir7.1 function. Both small molecule read-through drug and gene-therapy approaches were tested using this disease-in-a-dish approach.ResultsWe found that the LCA16 hiPSC-RPE had normal morphology but did not express a functional Kir7.1 channel and was unable to demonstrate normal physiology. Following read-through drug treatment, the LCA16 hiPSC cells were hyperpolarized by 30 mV and Kir7.1 current was restored. Similarly, loss-of-function of Kir7.1 channel was circumvented by lentiviral gene delivery to the hiPSC-RPE cells. In either approach, Kir7.1 protein was expressing normally with restoration of membrane potential and Kir7.1 current.ConclusionLoss-of-function mutation in Kir7.1 is a cause of LCA. Using either read-through therapy or gene augmentation, we rescued Kir7.1 channel function in patient-derived iPSC-RPE cells via a precision medicine approach.

Cyclic guanosine 3',5'-monophosphate (cGMP) inhibited the generation of pacemaker activity in interstitial cells of Cajal (ICCs) from the small intestine. However, cGMP role on pacemaker activity in colonic ICCs has not been reported yet. Thus, we investigated the role of cGMP in pacemaker activity regulation by colonic ICCs. We performed a whole-cell patch-clamp and Ca(2+) imaging in cultured ICCs from mouse colon. 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) increased the pacemaker potential frequency, whereas zaprinast (an inhibitor of phosphodiesterase) and cell-permeable 8-bromo-cGMP decreased the pacemaker potential frequency. KT-5823 (an inhibitor of protein kinase G [PKG]) did not affect the pacemaker potential. L-N(G)-nitroarginine methyl ester (L-NAME, an inhibitor of nitric oxide [NO] synthase) increased the pacemaker potential frequency, whereas (±)-S-nitroso-N-acetylpenicillamine (SNAP, a NO donor) decreased the pacemaker potential frequency. Glibenclamide (an ATP-sensitive K(+) channel blocker) did not block the effects of cell-permeable 8-bromo-cGMP and SNAP. Recordings of spontaneous intracellular Ca(2+) ([Ca(2+)]i) oscillations revealed that ODQ and L-NAME increased [Ca(2+)]i oscillations. In contrast, zaprinast, 8-bromo cGMP, and SNAP decreased the [Ca(2+)]i oscillations. Basal cGMP levels regulate the resting pacemaker potential frequency by the alteration on Ca(2+) release via a PKG-independent pathway. Additionally, the endogenous release of NO seems to be responsible maintaining basal cGMP levels in colonic ICCs.

Abnormal migration and proliferation of endothelial cells (EC) drive neovascular retinopathies. While anti-VEGF treatment slows progression, pathology is often supported by decrease in intraocular pigment epithelium-derived factor (PEDF), an endogenous inhibitor of angiogenesis. A surface helical 34-mer peptide of PEDF, comprising this activity, is efficacious in animal models of neovascular retina disease but remains impractically large for therapeutic use. We sought smaller fragments within this sequence that mitigate choroidal neovascularization (CNV). Expecting rapid intravitreal (IVT) clearance, we also developed a method to reversibly attach peptides to nano-carriers for extended delivery. Synthetic fragments of 34-mer yielded smaller anti-angiogenic peptides, and N-terminal capping with dicarboxylic acids did not diminish activity. Charge restoration via substitution of an internal aspartate by asparagine improved potency, achieving low nM apoptotic response in VEGF-activated EC. Two optimized peptides (PEDF 335, 8-mer and PEDF 336, 9-mer) were tested in a mouse model of laser-induced CNV. IVT injection of either peptide, 2–5 days before laser treatment, gave significant CNV decrease at day +14 post laser treatment. The 8-mer also decreased CNV, when administered as eye drops. Also examined was a nanoparticle-conjugate (NPC) prodrug of the 9-mer, having positive zeta potential, expected to display longer intraocular residence. This NPC showed extended efficacy, even when injected 14 days before laser treatment. Neither inflammatory cells nor other histopathologic abnormalities were seen in rabbit eyes harvested 14 days following IVT injection of PEDF 336 (>200 μg). No rabbit or mouse eye irritation was observed over 12–17 days of PEDF 335 eye drops (10 mM). Viability was unaffected in 3 retinal and 2 choroidal cell types by PEDF 335 up to 100 μM, PEDF 336 (100 μM) gave slight growth inhibition only in choroidal EC. A small anti-angiogenic PEDF epitope (G- Y - D - L-Y-R-V ) was identified, variants (adipic-Sar- Y - N - L-Y-R-V ) mitigate CNV, with clinical potential in treating neovascular retinopathy. Their shared active motif, Y - - - R, is found in laminin (Ln) peptide YIGSR, which binds Ln receptor 67LR, a known high-affinity ligand of PEDF 34-mer.

Background Hyperpolarization-activated cyclic nucleotide (HCN) channels are pacemaker channels that regulate heart rate and neuronal rhythm in spontaneously active cardiac and neuronal cells. Interstitial cells of Cajal (ICCs) are also spontaneously active pacemaker cells in the gastrointestinal tract. Here, we investigated the existence of HCN channel and its role on pacemaker activity in colonic ICCs. Methods We performed whole-cell patch clamp, RT-PCR, and Ca2+-imaging in cultured ICCs from mouse mid colon. Results SQ-22536 and dideoxyadenosine (adenylate cyclase inhibitors) decreased the frequency of pacemaker potentials, whereas both rolipram (cAMP-specific phosphodiesterase inhibitor) and cell-permeable 8-bromo-cAMP increased the frequency of pacemaker potentials. CsCl, ZD7288, zatebradine, clonidine (HCN channel blockers), and genistein (a tyrosine kinase inhibitor) suppressed the pacemaker activity. RT-PCR revealed expression of HCN1 and HCN3 channels in c-kit and Ano1 positive colonic ICCs. In recordings of spontaneous intracellular Ca2+ [Ca2+]i oscillations, rolipram and 8-bromo-cAMP increased [Ca2+]i oscillations, whereas SQ-22536, CsCl, ZD7288, and genistein decreased [Ca2+]i oscillations. Conclusions HCN channels in colonic ICCs are tonically activated by basal cAMP production and participate in regulation of pacemaking activity.

We studied whether nitric oxide (NO) and hydrogen sulfide (H(2)S) have an interaction on the pacemaker activities of interstitial cells of Cajal (ICC) from the mouse small intestine. The actions of NO and H(2)S on pacemaker activities were investigated by using the whole-cell patch-clamp technique and intracellular Ca(2+) analysis at 30℃ in cultured mouse ICC. Exogenously applied (±)-S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, or sodium hydrogen sulfide (NaHS), a donor of H(2)S, showed no influence on pacemaker activity (potentials and currents) in ICC at low concentrations (10 µM SNAP and 100 µM NaHS), but SNAP or NaHS completely inhibited pacemaker amplitude and pacemaker frequency with increases in the resting currents in the outward direction at high concentrations (SNAP 100 µM and NaHS 1 mM). Co-treatment with 10 µM SNAP plus 100 µM NaHS also inhibited pacemaker amplitude and pacemaker frequency with increases in the resting currents in the outward direction. ODQ, a guanylate cyclase inhibitor, or glibenclamide, an ATP-sensitive K(+) channel inhibitor, blocked the SNAP+NaHS-induced inhibition of pacemaker currents in ICC. Also, we found that SNAP+NaHS inhibited the spontaneous intracellular Ca(2+) ([Ca(2+)](i)) oscillations in cultured ICC. In conclusion, this study describes the enhanced inhibitory effects of NO plus H(2)S on ICC in the mouse small intestine. NO+H(2)S inhibited the pacemaker activity of ICC by modulating intracellular Ca(2+). These results may be evidence of a physiological interaction of NO and H(2)S in ICC for modulating gastrointestinal motility.

BACKGROUND/AIMS Capsaicin (8-methyl-N-vanillyl-6-ninenamide), a compound found in hot peppers, has been reported to have different physiological actions on different cell types. Not much work has been done about the effect of capsaicin on the function of interstitial cells of Cajal (ICC). In the present study, we examined the action of external application of capsaicin on pacemaker activity in the cultured ICC from the small intestine of mouse. METHODS We investigated the effect of capsaicin on pacemaker currents in cultured ICC from the small intestine of mouse using a whole cell patch-clamp technique and Ca(2+)-imaging analysis. RESULTS When capsaicin was applied externally to the pacemaker generating ICC, it completely inhibited the pacemaker potential under current-clamp mode (I = 0) and the pacemaker current under voltage-clamp mode at a -70 mV of holding potentials. The effect of capsaicin on pacemaker activity in ICC was shown dose dependently. The effect of capsaicin was not through the transient receptor potential of the vanilloid type 1 (TRPV1) channel as capsazepine did not block the effect of capsaicin. L-NAME, an inhibitor of nitric oxide synthase, also did not block the capsaicin-induced effects. When the action of capsaicin was examined in the intracellular calcium oscillation, it completely abolished the calcium oscillation. CONCLUSIONS These results prove that the capsaicin has the inhibitory effects on the ICC which is carried out neither through TRPV channel nor the nitric oxide production. Intracellular Ca(2+) was also an important target for actions of capsaicin on ICC.

Mutations in the KCNJ13 gene that encodes the inwardly rectifying potassium channel Kir7.1 cause snowflake vitreoretinal degeneration (SVD) and leber congenital amaurosis (LCA). Kir7.1 controls the microenvironment between the photoreceptors and the retinal pigment epithelium (RPE) and also contributes to the function of other organs such as uterus and brain. Heterologous expressions of the mutant channel have suggested a dominant-negative loss of Kir7.1 function in SVD, but parallel studies in LCA16 have been lacking. Herein, we report the identification of a novel nonsense mutation in the second exon of the KCNJ13 gene that leads to a premature stop codon in association with LCA16. We have determined that the mutation results in a severe truncation of the Kir7.1 C-terminus, alters protein localization, and disrupts potassium currents. Coexpression of the mutant and wild-type channel has no negative influence on the wild-type channel function, consistent with the normal clinical phenotype of carrier individuals. By suppressing Kir7.1 function in mice, we were able to reproduce the severe LCA electroretinogram phenotype. Thus, we have extended the observation that Kir7.1 mutations are associated with vision disorders to include novel insights into the molecular mechanism of disease pathobiology in LCA16.

Interstitial cells of Cajal (ICC) are the pacemaker cells that generate the rhythmic oscillation responsible for the production of slow waves in gastrointestinal smooth muscle. Spingolipids are known to present in digestive system and are responsible for multiple important physiological and pathological processes. In this study, we are interested in the action of sphingosine 1-phosphate (S1P) on ICC. S1P depolarized the membrane and increased tonic inward pacemaker currents. FTY720 phosphate (FTY720P, an S1P(1,3,4,5) agonist) and SEW 2871 (an S1P(1) agonist) had no effects on pacemaker activity. Suramin (an S1P(3) antagonist) did not block the S1P-induced action on pacemaker currents. However, JTE-013 (an S1P(2) antagonist) blocked the S1P-induced action. RT-PCR revealed the presence of the S1P(2) in ICC. Calphostin C (a protein kinase C inhibitor), NS-398 (a cyclooxygenase-2 inhibitor), PD 98059 (a p42/44 inhibitor), or SB 203580 (a p38 inhibitor) had no effects on S1P-induced action. However, c-jun NH(2)-terminal kinase (JNK) inhibitor II suppressed S1P-induced action. External Ca(2+)-free solution or thapsigargin (a Ca(2+)-ATPase inhibitor of endoplasmic reticulum) suppressed action of S1P on ICC. In recording of intracellular Ca(2+) ([Ca(2+)](i)) concentration using fluo-4/AM S1P increased intensity of spontaneous [Ca(2+)](i) oscillations in ICC. These results suggest that S1P can modulate pacemaker activity of ICC through S1P(2) via regulation of external and internal Ca(2+) and mitogenactivated protein kinase activation.

Lipopolysaccharide (LPS) induces intestinal dysmotility by alteration of smooth muscle and enteric neuronal activities. However, there is no report on the modulatory effects of LPS on the interstitial cells of Cajal (ICCs). We investigated the effect of LPS and its signal transduction in ICCs.We performed whole-cell patch clamp and RT-PCR in cultured ICCs from mouse small intestine.LPS suppressed the generation of pacemaker currents of ICCs. The mRNA transcripts for Toll-like receptor 4 (TLR4) were expressed in ICCs. However, the inhibitory action of LPS on pacemaker currents from TLR4(+/+) mice was not present in TLR4(-/-) mice. The inhibitory effects of LPS on ICCs were blocked by glibenclamide (an inhibitor of ATP-sensitive K(+) channels), NS-398 (a COX-2 inhibitor), AH6808 [a prostaglandin E(2) (PGE(2))-EP(2) receptor antagonist], ODQ (an inhibitor of guanylate cyclase) and L-NAME [an inhibitor of nitric oxide synthase (NOS)]. Furthermore, genistein and herbimycin A (tyrosine kinase inhibitors) blocked the LPS-induced inhibitory action on pacemaker activity in ICCs.LPS can activate ICCs to release NO and PGE(2) through TLR4 activation. The released NO and PGE(2) inhibit pacemaker currents by activating ATP-sensitive K(+) channels. The LPS actions are mediated by tyrosine kinase signaling pathways.

Neurotensin, a tridecapeptide localized in the gut to discrete enteroendocrine cells of the small bowel mucosa, is a hormone that plays an important role in gastrointestinal secretion, growth, and motility. Neurotensin has inhibitory and excitatory effects on peristaltic activity and produces contractile and relaxant responses in intestinal smooth muscle. Our objective in this study is to investigate the effects of neurotensin in small intestinal interstitial cells of Cajal (ICC) and elucidate the mechanism. To determine the electrophysiological effects of neurotensin on ICC, whole-cell patch clamp recordings were performed in cultured ICC from the small intestine. Exposure to neurotensin depolarized the membrane of pacemaker cells and produced tonic inward pacemaker currents. Only neurotensin receptor1 was identified when RT-PCR and immunocytochemistry were performed with mRNA isolated from small intestinal ICC and c-Kit positive cells. Neurotensin-induced tonic inward pacemaker currents were blocked by external Na+- free solution and in the presence of flufenamic acid, an inhibitor of non-selective cation channels. Furthermore, neurotensin-induced action is blocked either by treatment with U73122, a phospholipase C inhibitor, or thapsigargin, a Ca2+-ATPase inhibitor in ICC. We found that neurotensin increased spontaneous intracellular Ca2+ oscillations as seen with fluo4/AM recording. These results suggest that neurotensin modulates pacemaker currents via the activation of non-selective cation channels by intracellular Ca2+-release through neurotensin receptor1.

The effects of (-)-epigallocatechin gallate (EGCG) on pacemaker activities of cultured interstitial cells of Cajal (ICC) from murine small intestine were investigated using whole-cell patch-clamp technique at 30 and Ca(2+) image analysis. ICC generated spontaneous pacemaker currents at a holding potential of -70 mV. The treatment of ICC with EGCG resulted in a dose-dependent decrease in the frequency and amplitude of pacemaker currents. SQ-22536, an adenylate cyclase inhibitor, and ODQ, a guanylate cyclase inhibitor, did not inhibit the effects of EGCG. EGCG-induced effects on pacemaker currents were not inhibited by glibenclamide, an ATP-sensitive K(+) channel blocker and TEA, a Ca(2+)-activated K(+) channel blocker. Also, we found that EGCG inhibited the spontaneous [Ca(2+)](i) oscillations in cultured ICC. In conclusion, EGCG inhibited the pacemaker activity of ICC and reduced [Ca(2+)](i) oscillations by cAMP-, cGMP-, ATP-sensitive K+ channel-independent manner.

AIM: To investigate lipopolysaccharide (LPS) related signal transduction in interstitial cells of Cajal (ICCs) from mouse small intestine. METHODS: For this study, primary culture of ICCs was prepared from the small intestine of the mouse. LPS was treated to the cells prior to measurement of the membrane currents by using whole-cell patch clamp technique. Immunocytochemistry was used to examine the expression of the proteins in ICCs. RESULTS: LPS suppressed the pacemaker currents of ICCs and this could be blocked by AH6809, a prostaglandin E2-EP2 receptor antagonist or NG-Nitro-L-arginine Methyl Ester, an inhibitor of nitric oxide (NO) synthase. Toll-like receptor 4, inducible NO synthase or cyclooxygenase-2 immunoreactivity by specific antibodies was detected on ICCs. Catalase (antioxidant agent) had no action on LPS-induced action in ICCs. LPS actions were blocked by nuclear factor κB (NF-κB) inhibitor, actinomycin D (a gene transcription inhibitor), PD 98059 (a p42/44 mitogen-activated protein kinases inhibitor) or SB 203580 [a p38 mitogen-activated protein kinases (MAPK) inhibitor]. SB 203580 also blocked the prostaglandin E2-induced action on pacemaker currents in ICCs but not NO. CONCLUSION: LPS inhibit the pacemaker currents in ICCs via prostaglandin E2- and NO-dependent mechanism through toll-like receptor 4 and suggest that MAPK and NF-κB are implicated in these actions.

In this study we determined whether or not 5-hydroxytryptamine (5-HT) has an effect on the pacemaker activities of interstitial cells of Cajal (ICC) from the mouse small intestine. The actions of 5-HT on pacemaker activities were investigated using a whole-cell patch-clamp technique, intracellular Ca(2+) ([Ca(2+)](i)) analysis, and RT-PCR in ICC. Exogenously-treated 5-HT showed tonic inward currents on pacemaker currents in ICC under the voltage-clamp mode in a dose-dependent manner. Based on RT-PCR results, we found the existence of 5-HT(2B, 3, 4, and 7) receptors in ICC. However, SDZ 205557 (a 5-HT(4) receptor antagonist), SB 269970 (a 5-HT7 receptor antagonist), 3-tropanylindole - 3 - carboxylate methiodide (3-TCM; a 5-HT(3) antagonist) blocked the 5-HT-induced action on pacemaker activity, but not SB 204741 (a 5-HT(2B) receptor antagonist). Based on [Ca(2+)](i) analysis, we found that 5-HT increased the intensity of [Ca(2+)](i). The treatment of PD 98059 or JNK II inhibitor blocked the 5-HT-induced action on pacemaker activity of ICC, but not SB 203580. In summary, these results suggest that 5-HT can modulate pacemaker activity through 5-HT(3, 4, and 7) receptors via [Ca(2+)](i) mobilization and regulation of mitogen-activated protein kinases.

Background The bromodomain and extraterminal domain (BET) family proteins (BET2, BET3, and BET4) “read” (bind) histone acetylation marks via two distinct bromodomains (Brom1 and Brom2) facilitating transcriptional activation. These epigenetic “readers” play crucial roles in pathogenic processes such as inflammation. The role of BETs in influencing the degenerative process in the retina is however unknown. Methods We employed the rd10 mouse model (Pde6b rd10 mutation) of retinitis pigmentosa (RP) to examine the involvement of BET proteins in retinal neurodegeneration. Results Inhibition of BET activity by intravitreal delivery of JQ1, a BET-specific inhibitor binding both Brom1 and Brom2, ameliorated photoreceptor degeneration and improved electroretinographic function. Rescue effects of JQ1 were related to the suppression of retinal microglial activation in vivo, as determined by decreased immunostaining of activation markers (IBA1, CD68, TSPO) and messenger RNA (mRNA) levels of inflammatory cytokines in microglia purified from rd10 retinas. JQ1 pre-treatment also suppressed microglial activation in vitro, decreasing microglial proliferation, migration, and mRNA expression of inflammatory cytokines (TNFα, MCP-1, IL-1β, IL-6, and RANTES). Expression of BET2, but not BET3 and BET4, was significantly elevated during photoreceptor degeneration at postnatal day (PN)24 in retinas of rd10 mice relative to age-matched wild-type controls. siRNA knockdown of BET2 but not BET4, and the inhibitor of Brom2 (RVX208) but not of Brom1 (Olinone), decreased microglial activation. Conclusions These findings indicate that BET inhibition rescues photoreceptor degeneration likely via the suppression of microglial activation and implicates BET interference as a potential therapeutic strategy for the treatment of degenerative retinal diseases. Electronic supplementary material The online version of this article (doi:10.1186/s12974-016-0775-4) contains supplementary material, which is available to authorized users.