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Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complicated inflammatory disease, and the underlying mechanism remains unclear. While some reactive oxygen/nitrogen species-related gene products are reported to participate in CRSwNP, a systemic and full analysis of oxidative-stress-associated genes in CRSwNP has not been extensively studied. Therefore, this study sought to catalog the gene-expression patterns related to oxidative stress and antioxidant defense in control and CRSwNP patients. In total, 25 control and 25 CRSwNP patients were recruited. The distribution and expression of 4-hydroxynonenal and 3-nitrotyrosine as markers of oxidative stress—which is represented by lipid peroxidation and the protein nitration of tyrosine residues in CRSwNP nasal polyps (NPs)—were more apparently increased than those found in the control nasal mucosae, as determined by immunohistochemistry (IHC). The expression of 84 oxidative-stress-related genes in nasal mucosae and NP tissues was analyzed via real-time PCR, which showed that 19 genes and 4 genes were significantly up- and downregulated, respectively; among them, inducible nitric oxide synthase (iNOS) and heme oxygenase 1 (HO-1) were notably upregulated, whereas lactoperoxidase (LPO), myeloperoxidase (MPO), and superoxide dismutase 3 (SOD3) were highly downregulated. Changes in the mRNA and protein levels of these redox proteins were confirmed with a customized, real-time PCR array and RT-PCR analysis, as well as Western blotting and IHC assays. A receiver operating characteristic curve analysis further suggested that LPO, MPO, SOD3, HO-1, and iNOS are possible endotype predictors of CRSwNP development. Collectively, we present an oxidative-stress-related gene profile of CRSwNP NP tissues, providing evidence that the systemic changes in oxidative stress and the antioxidative defense system, including novel iNOS, heme peroxidases, and other genes, are closely linked to CRSwNP pathology, development, and progression. [ABSTRACT FROM AUTHOR]

Vitamin E was previously reported to reduce calcium oxalate (CaOx) crystal formation. This study explored whether vitamin E deficiency affects intrarenal oxidative stress and accelerates crystal deposition in hyperoxaluria. The control (C) group of rats received a standard diet and drinking water, while the experimental groups received 0.75% ethylene glycol (EG) in drinking water for 42 days. Of the latter, one group received a standard diet (EG group), one received a low-vitamin E (LE) diet (EG+LE group), and the last received an LE diet with vitamin E supplement (4 mg) (EG+LE+E group). The C+LE and C+LE+E groups were the specific controls for the last two experimental groups, respectively. In a separate experiment, EG and EG+LE rats were studied on days 3-42 to examine the temporal relationship between oxidative change and crystal formation. Urinary biochemistry and activity/levels of antioxidative and oxidative enzymes in glomeruli and tubulointerstitial specimens (TIS) were examined. In EG rats, CaOx crystal accumulation was associated with low antioxidative enzyme activity in TIS and with increased oxidative enzyme expression in glomeruli. In the EG+LE group, marked changes in antioxidative and oxidative enzyme levels were seen and correlated with massive CaOx deposition and tubular damage. The increased oxidative stress seen with EG+LE treatment was largely reversed by vitamin E supplementation. A temporal study showed that decrease in antioxidative defense and increased free radical formation in the EG+LE group occurred before crystal deposition. This study shows that low vitamin E disrupts the redox balance and causes cell death, thereby favoring crystal formation. antioxidative proteins; free radicals; hyperoxaluria

Hyperoxaluric kidneys show an impaired diuretic response to acute infusion of L-arginine. In this study, we examined the chronic effect of L-arginine supplementation on CaOx crystal formation in hyperoxaluric rat kidneys. Eight groups were tested: control (received drinking water), L group (received L-arginine, 0.6%), LN group [received [N.sup.G]-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg)], L + LN group (received L-arginine + L-NAME), HP group [received hydroxyl-L-proline (HP, 5%) mixed with chow to induce hyperoxaluria], L + HP group (received HP + t.-arginine), HP + LN group, and L + HP + LN group. The duration was 42 days, and each group had eight animals. Urinary biochemistry and renal CaOx amounts were measured, as well as renal expressions of nitric oxide synthase (NOS) isoforms and NAD(P)H oxidase. The distribution of inducible NOS (iNOS), NAD(P)H oxidase, ED1-positive cells, and nitrotyrosine was examined by immunohistochemical and immunofluorescence studies, whereas superoxide production from the kidneys was examined by fluorescence spectrometric assay. Compared with the HP group, the L + HP group had excessive CaOx crystal accumulation and enhanced endothelial NOS (eNOS), iNOS, and NAD(P)H oxidase protein expression in the kidney. Urinary excretion of nitrotyrosine was markedly increased. Increased superoxide formation in the L + HP kidney was derived from NAD(P)H oxidase and uncoupled eNOS, and increased nitrotyrosine formation might derive from iNOS and EDl-positive cells that gathered around the CaOx crystals. L-NAME cotreatment (L + HP + LN group) reduced renal oxidative nitrosative stress and tubular damage, which were induced by L + HP. The results showed that chronic L-arginine treatment to the hyperoxaluric kidney with massive CaOx crystal deposition may have a toxic effect by enhancing intrarenal oxidative and nitrosative stress. hyperoxaluria; nephrolithiasis; NAD(P)H oxidase; nitric oxide synthase

N-methyl-D-aspartate (NMDA) receptor activated by glutamate/glycine is located in the kidneys. The NMDA receptor subunit NRI is increased in damaged renal tissue. This study explored the role of NMDA receptors in ischemia-reperfusion-induced renal dysfunction in rats. With Western blot analysis and renal functional assay, NMDA receptor expression was evaluated, as well as its functional role in female Wistar rat kidneys after 45 min of unilateral ischemia followed by 24 h of reperfusion. The effects of intrarenal NMDA receptor agonist and antagonist on renal blood flow (RBF), glomerular filtration rate (GFR), urine volume (UV), sodium (UNaV), and potassium (UKV) excretion were determined. NMDA NR1 was present in the glomeruli, brush-border membrane, and outer medulla but not in the cortex and inner medulla. Homogenous distribution of non-NMDA GluR2/3, sparse kainate KAI, and undetectable group I of metabotropic glutamate receptor were noted in the control kidneys. Ischemia-reperfusion kidneys showed enhanced renal NR1, but not NR2C and GluR2/3 expression, and were associated with decreased GFR/RBF and natriuretic/diuretic responses. Intrarenal NMDA agonists significantly reduced GFR, UV, UNaV, and UKV but had no effect on blood pressure and RBF in sham control and ischemia-reperfusion kidneys. NMDA antagonist D-2-amino-5-phosphonopentanoic acid (D-AP-5) treatment completely abolished NMDA-induced renal dysfunction. D-AP-5 treatment significantly ameliorated ischemia-reperfusion-induced glomerular and tubular dysfunction by restoring decreased GFR, UV, and [U.sub.Na]V levels. Ischemia-reperfusion upregulates renal NMDA NR1 receptor expression, leading to reduced glomerular and tubular function in the kidneys. The NMDA antagonist can ameliorate ischemia-reperfusion-induced renal dysfunction. ischemia-reperfusion; kidney; glutamate; renal function

Stimulation of capsaicin receptors results in an increase in afferent renal nerve activity (ARNA), but it is unclear how capsaicin contributes to sensory activation intrarenally. Here, we studied the relationships between capsaicin receptor activation, substance P (SP) release, and the sensory response in the rat renal pelvis. Immunoblots showed that one of the capsaicin receptors, transient receptor potential vanilloid type 1 channel (TRPV1), was found in various renal tissues and was especially abundant in the renal pelvis, where most sensory nerve fibers originate. Interestingly, immunolabeling showed colocalization of TRPV1, SP, and the panneuronal marker PGP9.5 in the renal pelvis. Electrophysiological recordings showed that SP and capsaicin activated the same mechanosensitive ARNA in a single-unit preparation. Intrapelvic administration of capsaicin or a specific TRPV1 agonist, resiniferatoxin, resulted in a dose-dependent increase in multi-unit ARNA and SP release, and these effects were blocked by the TRVP1 blocker capsazepine. Inhibition of the SP receptor by L-703,606 largely prevented capsaicin- or resiniferatoxin-induced ARNA. Capsazepine also prevented intrapelvic pressure (IPP)-dependent ARNA activation and contralateral diuresis/natriuresis in the renorenal reflex at an IPP of 20 mmHg, but had no effect at an IPP of 50 mmHg. These data indicate that TRPV1, a low-pressure baroreceptor, is present in the renal pelvis and exclusively regulates neuropeptide release from primary renal afferent C-fibers in response to mechanostimulation. neurokinin-1 receptor; renorenal reflex; capsaicin receptor; intrapelvic pressure

Temporal decrease in renal sensory responses in rats after chronic ligation of the bile duct. Am J Physiol Renal Physiol 283: F164-F172, 2002. First published February 19, 2002; 10.1152/ajprenal.00231.2001.--Renal responses to renal sensory receptor activation were examined in rats after 1 and 4 wk of common bile duct ligation (CBDL). Compared with sham-operated rats (Sham), urine and sodium excretion after acute saline loading was significantly reduced at both times after CBDL. The blunted excretory responses in CBDL rats, accompanied by less activation of afferent renal nerve activity (ARNA), were already apparent at 1 wk and became severe at 4 wk. The defect in ARNA activation in CBDL rats was further studied using specific stimuli to activate renal sensory receptors. Graded increases in intrapelvic pressure or renal pelvic perfusion of substance P (SP) elicited an increase in ARNA in Sham rats, these responses being temporally attenuated in CBDL rats. Despite no significant change in renal pelvic SP release, no renorenal reflex was demonstrable in 4-wk CBDL rats. Immunoblotting showed that expression of renal pelvic neurokinin 1 (NK-1) receptors was 32 and 47% lower in 1- and 4-wk CBDL rats, respectively, than in Sham rats, this decrease correlating well with plasma SP levels. The quantitative real-time RT-PCR showed similar levels of NK-1 receptor mRNA in the renal pelvis in the Sham and 4-wk CBDL groups. We conclude that impairment of renal excretory and sensory responses increases with the duration of cirrhosis. An impaired renorenal reflex in cirrhotic rats is involved in the defective activation of the renal sensory receptors could be due, in part, to the low expression of NK-1 receptors, which is dependent on the duration of CBDL. The decrease in NK-1 receptor protein levels is not due to a decrease in mRNA levels. afferent renal nerve activity; renorenal reflex; substance P; neurokinin 1 receptor; cirrhosis

We previously demonstrated that the pulmonary vascular response to substance P (SP) increased in chronically hypoxic rats. This study explored the temporal increase in reactivity of the pulmonary vascular response to SP and its underlying mechanisms. First, young female Wistar rats were exposed to sea level (SL) or simulated high altitude (HA) for 15 h/day for 3 days, 1 wk, 2 wk, and 4 wk. Lungs were isolated and perfused with 4% bovine serum albumin in Krebs-Henseleit buffer solution. SP (1.5 x [10.sup.-4] M) induced significant increases in pulmonary arterial pressure ([P.sub.pa]), venous pressure ([P.sub.v]), capillary pressure ([P.sub.c]), arterial resistance ([R.sub.a]), and filtration coefficient ([K.sub.fc]) in SL lungs. Increases in [P.sub.pa] and [R.sub.a] were significantly augmented in HA lungs, with a temporal increase trend peaking at 2 wk of HA exposure. The selective neurokinin (NK) type 1 (N[K.sub.1]) receptor antagonist SR-14033 significantly attenuated SP-induced increases in [P.sub.pa], [P.sub.v], [P.sub.c], [R.sub.a], and [K.sub.fc] in SL lungs. In lungs exposed to HA for 2 wk, SR-14033 suppressed the effect of SP on [P.sub.pa]. Also, chronic hypoxia induced significant increases in N[K.sub.1] receptors and N[K.sub.1] receptor mRNA, with a temporal trend. We conclude that chronic hypoxia temporally augments SP-induced vascular responses, which are closely associated with increases in N[K.sub.1] receptors and gene expression. pulmonary hypertension; tachykinins; gene expression

A higher expression level of mitogenic fibroblast growth factor‐2 (FGF‐2) has been reported in human nasal mucus of both chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP). Meanwhile, we have shown that long pentraxin 3 (PTX3), an essential component of humoral innate immunity that is produced at sites of infection and inflammation, was overproduced in human nasal mucosae and secretions of CRSsNP. Therefore, this study was aimed to investigate how FGF‐2 regulates PTX3 expression in human CRSsNP nasal mucosa‐derived fibroblast cells (hNMDFs). The FGF‐2 treatment caused ptx3 mRNA expression and PTX3 protein induction and secretion. In parallel, a differential expression of FGF receptor (FGFR)−1 to FGFR‐4 was observed in hNMDFs and human nasal tissues. While conventionally known PI3K/Akt/mTOR and AP‐1 pathways following FGFR activation were shown to be involved, the protein kinase Cδ (PKCδ) and cAMP response element‐binding protein (CREB) were also found to be as critical signaling molecules in FGF‐2‐induced PTX3 induction. The PKCδ and CREB activation could be detected in total cells and in the cell nucleus. Accordingly, a novel CREB binding sequence was detected in the human ptx3 promoter region and could interact with activated CREB in cells challenged with FGF‐2. Surprisingly, the phospholipase D (PLD), but not phosphoinositide‐ and phosphatidylcholine‐phospholipase C, was necessarily required for PKCδ and CREB activation. Therefore, we demonstrated here for the first time that FGF‐2 mediates PTX3 production not only through PI‐3K/Akt/mTOR and AP‐1 activation, but also through a novel FGFR–PLD–PKCδ–CREB cellular signaling pathway. [ABSTRACT FROM AUTHOR]

Ischemic neuron loss contributes to brain dysfunction in patients with cardiac arrest (CA). Histidine–tryptophan–ketoglutarate (HTK) solution is a preservative used during organ transplantation. We tested the potential of HTK to protect neurons from severe hypoxia (SH) following CA. We isolated rat primary cortical neurons and induced SH with or without HTK. Changes in caspase-3, hypoxia-inducible factor 1-alpha (HIF-1α), and nicotinamide adenine dinucleotide phosphate oxidase-4 (NOX4) expression were evaluated at different time points up to 72 h. Using a rat asphyxia model, we induced CA-mediated brain damage and then completed resuscitation. HTK or sterile saline was administered into the left carotid artery. Neurological deficit scoring and mortality were evaluated for 3 days. Then the rats were sacrificed for evaluation of NOX4 and H2O2 levels in blood and brain. In the in vitro study, HTK attenuated SH- and H2O2-mediated cytotoxicity in a volume- and time-dependent manner, associated with persistent HIF-1α expression and reductions in procaspase-3 activation and NOX4 expression. The inhibition of HIF-1α abrogated HTK’s effect on NOX4. In the in vivo study, neurological scores were significantly improved by HTK. H2O2 level, NOX4 activity, and NOX4 gene expression were all decreased in the brain specimens of HTK-treated rats. Our results suggest that HTK acts as an effective neuroprotective solution by maintaining elevated HIF-1α level, which was associated with inhibited procaspase-3 activation and decreased NOX4 expression. [ABSTRACT FROM AUTHOR]

Enhanced sodium excretion is associated with intrarenal oxidative stress. The present study evaluated whether oxidative stress caused by high sodium (HS) may be involved in calcium oxalate crystal formation. Male rats were fed a sodium-depleted diet. Normal-sodium and HS diets were achieved by providing drinking water containing 0.3% and 3% NaCl, respectively. Rats were fed a sodium-depleted diet with 5% hydroxyl-L-proline (HP) for 7 and 42 days to induce hyperoxaluria and/or calcium oxalate deposition. Compared to normal sodium, HS slightly increased calcium excretion despite diuresis; however, the result did not reach statistical significance. HS did not affect the hyperoxaluria, hypocalciuria or supersaturation caused by HP; however, it increased calcium oxalate crystal deposition soon after 7 days of co-treatment. Massive calcium oxalate formation and calcium crystal excretion in HS+HP rats were seen after 42 days of treatment. HP-mediated hypocitraturia was further exacerbated by HS. Moreover, HS aggravated HP-induced renal injury and tubular damage via increased apoptosis and oxidative stress. Increased urinary malondialdehyde excretion, in situ superoxide production, NAD(P)H oxidase and xanthine oxidase expression and activity, and decreased antioxidant enzyme expression or activity in the HS+HP kidney indicated exaggerated oxidative stress. Interestingly, this redox imbalance was associated with reduced renal osteopontin and Tamm-Horsfall protein expression (via increased excretion) and sodium-dependent dicarboxylate cotransporter NaDC-1 upregulation. Collectively, our results demonstrate that a HS diet induces massive crystal formation in the hyperoxaluric kidney; this is not due to increased urinary calcium excretion but is related to oxidative injury and loss of anticrystallization defense. [ABSTRACT FROM AUTHOR]

The present results demonstrated that high glucose (G), salt (S), and cholesterol C (either alone or in combination), as mimicking extracellular changes in metabolic syndrome, damage cardiomyocyte-like H9c2 cells and reduce their viability in a time-dependent manner. However, the effects were greatest when cells were exposed to all three agents (GSC). The mRNA of glycoprotein (gp) 130 and WSX-1, both components of the interleukin (IL)-27 receptor, were present in H9c2 cells. Although mRNA expression was not affected by exogenous treatment with IL-27, the expression of gp130 mRNA (but not that of WSX-1 mRNA) was attenuated by GSC. Treatment of IL-27 to H9c2 cells increased activation of signal transducer and activator of transcription 3 (STAT3) and protected cells from GSC-induced cytochrome c release and cell damage. The protective effects of IL-27 were abrogated by the STAT3 inhibitor, stattic. The results of the present study clearly demonstrate that the STAT3 pathway triggered by anti-inflammatory IL-27 plays a role in protecting cardiomyocytes against GSC-mediated damage. [ABSTRACT FROM AUTHOR]

N-methyl-D-aspartate (NMDA) receptor activation in rat kidney reduces renal perfusion and ultrafiltration. Hypoperfusion-induced ischemia is the most frequent cause of functional insufficiency in the endotoxemic kidney. Here, we used non-hypotensive rat model of lipopolysaccharide-induced endotoxemia to examine whether NMDA receptor hyperfunction contributes to acute kidney injury. Lipopolysaccharide-induced renal damage via increased enzymuria and hemodynamic impairments were ameliorated by co-treatment with the NMDA receptor blocker, MK-801. The NMDA receptor NR1 subunit in the rat kidney mainly co-localized with serine racemase, an enzyme responsible for synthesizing the NMDA receptor co-agonist, D-serine. The NMDA receptor hyperfunction in lipopolysaccharide-treated kidneys was demonstrated by NR1 and serine racemase upregulation, particularly in renal tubules, and by increased D-serine levels. Lipopolysaccharide also induced cell damage in cultured tubular cell lines and primary rat proximal tubular cells. This damage was mitigated by MK-801 and by small interfering RNA targeting NR1. Lipopolysaccharide increased cytokine release in tubular cell lines via toll-like receptor 4. The release of interleukin-1β from these cells are the most abundant. An interleukin-1 receptor antagonist not only attenuated cell death but also abolished lipopolysaccharide-induced NR1 and serine racemase upregulation and increases in D-serine secretion, suggesting that interleukin-1β-mediated NMDA receptor hyperfunction participates in lipopolysaccharide-induced tubular damage. The results of this study indicate NMDA receptor hyperfunction via cytokine effect participates in lipopolysaccharide-induced renal insufficiency. Blockade of NMDA receptors may represent a promising therapeutic strategy for the treatment of sepsis-associated renal failure. [ABSTRACT FROM AUTHOR]

Ventilator-induced lung injury is associated with inflammatory mechanism and causes high mortality. The objective of this study was to discover the role of IL-33 and its ST2 receptor in acute lung injury induced by mechanical ventilator (ventilator-induced lung injury; VILI). Male Wistar rats were intubated after tracheostomy and received ventilation at 10 cm H2O of inspiratory pressure (PC10) by a G5 ventilator for 4 hours. The hemodynamic and respiratory parameters were collected and analyzed. The morphological changes of lung injury were also assessed by histological H&E stain. The dynamic changes of lung injury markers such as TNF-α and IL-1β were measured in serum, bronchoalveolar lavage fluid (BALF), and lung tissue homogenization by ELISA assay. During VILI, the IL-33 profile change was detected in BALF, peripheral serum, and lung tissue by ELISA analysis. The Il-33 and ST2 expression were analyzed by immunohistochemistry staining and western blot analysis. The consequence of VILI by H&E stain showed inducing lung congestion and increasing the expression of pro-inflammatory cytokines such as TNF-α and IL-1β in the lung tissue homogenization, serum, and BALF, respectively. In addition, rats with VILI also exhibited high expression of IL-33 in lung tissues. Interestingly, the data showed that ST2L (membrane form) was highly accumulated in the membrane fraction of lung tissue in the PC10 group, but the ST2L in cytosol was dramatically decreased in the PC10 group. Conversely, the sST2 (soluble form) was slightly decreased both in the membrane and cytosol fractions in the PC10 group compared to the control group. In conclusion, these results demonstrated that ST2L translocation from the cytosol to the cell membranes of lung tissue and the down-expression of sST2 in both fractions can function as new biomarkers of VILI. Moreover, IL-33/ST2 signaling activated by mechanically responsive lung injury may potentially serve as a new therapy target. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) was the third gasotransmitter to be recognized as a cytoprotectant. A recent study demonstrated that exogenous supplementation of H2S ameliorates functional insufficiency in chronic kidney disease (CKD). However, how the H2S system is impaired by CKD has not been elucidated. The uremic toxin indoxyl sulfate (IS) is known to accumulate in CKD patients and harm the renal tubular cells. This study therefore treated the proximal tubular cells, LLC-PK1, with IS to see how IS affects H2S formation. Our results showed that H2S release from LLC-PK1 cells was markedly attenuated by IS when compared with control cells. The H2S donors NaHS and GYY-4137 significantly attenuated IS-induced tubular damage, indicating that IS impairs H2S formation. Interestingly, IS downregulated the H2S-producing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST), and these effects could be reversed by inhibition of the IS receptor, aryl hydrocarbon receptor (AhR). As transcription factor specificity protein 1 (Sp1) regulates the gene expression of H2S-producing enzymes, we further showed that IS significantly decreased the DNA binding activity of Sp1 but not its protein expression. Blockade of AhR reversed low Sp1 activity caused by IS. Moreover, exogenous H2S supplementation attenuated IS-mediated superoxide formation and depletion of the cellular glutathione content. These results clearly indicate that IS activates AhR, which then attenuates Sp1 function through the regulation of H2S-producing enzyme expression. The attenuation of H2S formation contributes to the low antioxidant defense of glutathione in uremic toxin-mediated oxidative stress, causing tubular cell damage. [ABSTRACT FROM AUTHOR]

Aims The aim of the study was to test the hypothesis that the renal nitric oxide (NO) system is involved in the animal model of nephrolithiasis by evaluating the relationship between nitric oxide synthase (NOS) and oxidative stress. Methods Deposition of renal calculi was induced by adding 0.75% ethylene glycol (EG) to the drinking water of male Wistar rats. After 42 days of treatment, urinary biochemistry and urinary levels of oxalate, NO metabolites (nitrate and nitrite), cGMP, and lipid peroxides, and markers for renal damage and oxidative stress in the kidney were examined. In the second part of the experiment, two diuretic stimuli (intrarenal infusion of l-arginine or saline loading) were applied to test the renal NO system response. Finally, levels of three isoforms of NOS in renal tissues were evaluated by immunostaining. Results In the EG-treated rats, increased urinary excretion of enzymes and lipid peroxides and increased nitrotyrosine levels and oxidative injury markers in the kidneys indicated that peroxynitrite formation occurred during oxidative stress, while the 24-hr urinary excretion of NO metabolites and cGMP remained unchanged. In contrast to control rats, urinary excretion and NO metabolites and cGMP excretion were unresponsive to intrarenal l-arginine infusion; in response to saline loading, an increase in these factors was seen, but the increase was only 50% of that seen in the identically treated control group. A significant decrease in eNOS expression and increase in iNOS expression were observed in the renal medulla of the EG-treated group, whereas expression of nNOS was not affected. Conclusions Although basal renal NO production remained unchanged, excessive peroxynitrite formation in the kidney was noted in this model. A decreased response of the NOS system was noted when diuretic stimuli were applied. How the imbalance between eNOS and iNOS expression influences CaOx stone formation requires detailed evaluation. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Mice lacking Na+/H+ exchanger 1 (NHE1) show a unique epilepsy phenotype although the underlying mechanisms remain unclear. Since expression of delta-opioid receptor (DOR) may be involved in control of epileptic activity, we conducted immunohistochemistry and autoradiography to investigate whether DOR expression is dys-regulated in the brain of NHE1 null mouse. Immunohistochemistry showed a decline in DOR expression in hippocampus and cortex. Autoradiographic results confirmed that the density of DOR was decreased in most cortical and hippocampal regions such as striate and temporal cortex, hippocampal CA1 and CA3 regions (reduced by 27.7±6.4%, 29.4±5.1%, 40.7±4.4% and 20.6±5.7%, respectively, P <0.05). These data demonstrate that NHE1 null mutation leads to a reduction of DOR expression in the cortical and hippocampal regions, which provides a new clue for the genesis of epilepsy. [Copyright &y& Elsevier]

Renal ischaemia releases reactive oxygen species (ROS) in the kidneys. We hypothesized that the kidneys are more resistant to the insult of ROS in chronically hypoxic rats. We thus compared rats kept at sea level (SL) and those that had been adapted to hypoxia (hypoxia adapted, HA) by exposure to an altitude of 5500 m in an altitude chamber for 15 h day−1 for 4 weeks. Xanthine (X, 0.75 mg kg−1) and xanthine oxidase (XO, 24.8 mU kg−1) were injected intrarenally. A lucigenin‐enhanced chemiluminescence method was employed to detect the amount of free radicals in renal venous blood samples and on the kidney surface. In the renal venous blood samples, 26.05 (± 4.36) × 104 and 10.98 (± 1.79) × 104 counts were detected in the SL and HA rats, respectively, after X‐XO treatment; these figures were significantly different. On the kidney surface of the SL rats, the free radical count amounted to 12.77 (± 1.64) × 104, while that in the HA rats was 8.47 (± 0.42) × 104; these figures were also significantly different. There was a significant increase in urine volume and urinary excretion of Na+, K+ and protein after X‐XO administration in both groups of rats. However, the effect was greater for the SL rats than for the HA rats. The lipid peroxidation of the kidneys was not significantly different in the two groups of rats. Finally, we found that the activity of superoxide dismutase (SOD) and SOD mRNA were higher in the renal tissue of HA rats. We conclude that the renal response to free radicals is attenuated after chronic hypoxia in rats, and that SOD might play an important role in protecting HA rats from oxidative stress. [ABSTRACT FROM AUTHOR]

Inflammation worsens oxalate nephropathy by exacerbating tubular damage. The transient receptor potential vanilloid 1 (TRPV1) channel is present in kidney and has a polymodal sensing ability. Here, we tested whether TRPV1 plays a role in hyperoxaluria-induced renal inflammation. In TRPV1-expressed proximal tubular cells LLC-PK1, oxalate could induce cell damage in a time- and dose-dependent manner; this was associated with increased arachidonate 12-lipoxygenase (ALOX12) expression and synthesis of endovanilloid 12(S)-hydroxyeicosatetraenoic acid for TRPV1 activation. Inhibition of ALOX12 or TRPV1 attenuated oxalate-mediated cell damage. We further showed that increases in intracellular Ca2+ and protein kinase C α activation are downstream of TRPV1 for NADPH oxidase 4 upregulation and reactive oxygen species formation. These trigger tubular cell inflammation via increased NLR family pyrin domain-containing 3 expression, caspase-1 activation, and interleukin (IL)-1β release, and were alleviated by TRPV1 inhibition. Male hyperoxaluric rats demonstrated urinary supersaturation, tubular damage, and oxidative stress in a time-dependent manner. Chronic TRPV1 inhibition did not affect hyperoxaluria and urinary supersaturation, but markedly reduced tubular damage and calcium oxalate crystal deposition by lowering oxidative stress and inflammatory signaling. Taking all these results together, we conclude that TRPV1 hyperfunction contributes to oxalate-induced renal inflammation. Blunting TRPV1 function attenuates hyperoxaluric nephropathy. [ABSTRACT FROM AUTHOR]

The accumulation of the uremic toxin indoxyl sulfate (IS) induces target organ damage in chronic kidney disease (CKD) patients, and causes complications including cardiovascular diseases, renal osteodystrophy, muscle wasting, and anemia. IS stimulates reactive oxygen species (ROS) production in CKD, which impairs glomerular filtration by a direct cytotoxic effect on the mesangial cells. IS further reduces antioxidant capacity in renal proximal tubular cells and contributes to tubulointerstitial injury. IS-induced ROS formation triggers the switching of vascular smooth muscular cells to the osteoblastic phenotype, which induces cardiovascular risk. Low-turnover bone disease seen in early CKD relies on the inhibitory effects of IS on osteoblast viability and differentiation, and osteoblastic signaling via the parathyroid hormone. Excessive ROS and inflammatory cytokine releases caused by IS directly inhibit myocyte growth in muscle wasting via myokines' effects. Moreover, IS triggers eryptosis via ROS-mediated oxidative stress, and elevates hepcidin levels in order to prevent iron flux in circulation in renal anemia. Thus, IS-induced oxidative stress underlies the mechanisms in CKD-related complications. This review summarizes the underlying mechanisms of how IS mediates oxidative stress in the pathogenesis of CKD's complications. Furthermore, we also discuss the potential role of oral AST-120 in attenuating IS-mediated oxidative stress after gastrointestinal adsorption of the IS precursor indole. [ABSTRACT FROM AUTHOR]

R1971 --> Hydrogen sulfide (H2S) is the third gasotransmitter that recognized as a cytoprotectant. Recent study demonstrated that exogenous supplement of H2S ameliorates functional insufficiency in chronic kidney disease (CKD). However, how H2S system is impaired by CKD has not been elucidated. The uremic toxin indoxyl sulfate (IS) is known to accumulate in CKD patients and harm the renal tubular cells. This study therefore treated proximal tubular cells LLC‐PK1 with IS to see how IS affects H2S formation. Our results showed that H2S release from LLC‐PK1 cells was markedly attenuated by IS when compared to that in control cells. The H2S donors NaHS and GYY‐4137 significantly attenuated IS‐induced tubular damage by enhancing cell survival in dose‐dependent manners. Inhibition of remnant H2S production in the IS‐treated cells by AOAA exacerbated tubulotoxicity. These results clearly indicated IS impairs H2S formation. We then examined protein and mRNA expression of H2S‐producing enzymes cystathionine β‐synthase (CBS), cystathionine γ‐lyase (CSE), and 3‐mercaptopyruvate sulfurtransferase (3‐MST). IS downregulated both CBS and 3‐MST protein and mRNA expressions after 24‐72 h of treatment. CSE protein and mRNA levels were lowered at 24 h and 24‐48 h, respectively, by IS. The low expression of CBS and 3‐MST at both protein and mRNA levels could be reversed by AhR inhibition. As transcription factor specificity protein 1 (Sp1) regulates gene expression of H2S‐producing enzymes, we further showed that IS significantly decreased the DNA binding activity of Sp1, this however did not affect Sp1 protein expression. AhR inhibition reversed low Sp1 activity caused by IS. Together these results, we conclude that IS activates AhR which then attenuates Sp1 function on regulation of H2S‐producing enzyme expression. Attenuation of H2S formation contributed to uremic toxin‐mediated renal tubular cell damage. [ABSTRACT FROM AUTHOR]

Indoxyl sulfate (IS), a uremic toxin, causes chronic kidney disease (CKD) progression via its tubulotoxicity. After cellular uptake, IS directly induces apoptotic and necrotic cell death of tubular cells. Additionally, IS increases oxidative stress and decreases antioxidant capacity, which are associated with tubulointerstitial injury. Injured tubular cells are a major source of transforming growth factor-β1 (TGF-β1), which induces myofibroblast transition from residual renal cells in damaged kidney, recruits inflammatory cells and thereby promotes extracellular matrix deposition in renal fibrosis. Moreover, IS upregulates signal transducers and activators of transcription 3 phosphorylation, followed by increases in TGF-β1, monocyte chemotactic protein-1 and α-smooth muscle actin production, which participate in interstitial inflammation, renal fibrosis and, consequently, CKD progression. Clinically, higher serum IS levels are independently associated with renal function decline and predict all-cause mortality in CKD. The poor removal of serum IS in conventional hemodialysis is also significantly associated with all-cause mortality and heart failure incidence in end-stage renal disease patients. Scavenging the IS precursor by AST-120 can markedly reduce tubular IS staining that attenuates renal tubular injury, ameliorates IS-induced oxidative stress and rescues antioxidant glutathione activity in tubular epithelial cells, thereby providing a protective role against tubular injury and ultimately retarding renal function decline. [ABSTRACT FROM AUTHOR]

Indoxyl sulfate (IS) is accumulated during severe renal insufficiency and known for its nephrotoxic properties. Transient receptor potential vanilloid 1 (TRPV1) is present in the kidney and acts as a renal sensor. However, the mechanism underlying IS-mediated renal tubular damage in view of TRPV1 is lacking. Here, we demonstrated that TRPV1 was expressed in tubular cells of Lilly Laboratories cell-porcine kidney 1 (LLC-PK1) and Madin-Darby canine kidney cells (MDCK). IS treatment in both cells exhibited tubular damage with increased LDH release and reduced cell viability in dose- and time-dependent manners. MDCK, however, was more vulnerable to IS. We, therefore, investigated MDCK cells to explore a more detailed mechanism. Interestingly, IS-induced tubular damage was markedly attenuated in the presence of selective TRPV1 blockers. IS showed no effect on TRPV1 expression but significantly increased arachidonate 12-lipoxygenase (ALOX12) protein, mRNA expression, and 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) amounts in a dose-dependent manner, indicating that the ALOX12/12(S)-HETE pathway induced TRPV1 hyperfunction in IS-mediated tubulotoxicity. Blockade of ALOX12 by cinnamyl-3,4-dihydroxy-α-cyanocinnamate or baicalein attenuated the effects of IS. Since aryl hydrocarbon receptor (AhR) activation after IS binding is crucial in mediating cell death, here, we found that the AhR blockade not only ameliorated tubular damage but also attenuated ALOX12 expression and 12(S)-HETE production caused by IS. The uremic toxic adsorbent AST-120, however, showed little effect on ALOX12 and 12(S)-HETE, as well as IS-induced cell damage. These results clearly indicated that IS activated AhR and then upregulated ALOX12, and this induced endovanilloid 12(S)-HETE synthesis and contributed to TRPV1 hyperfunction in IS-treated tubular cells. Further study on TRPV1 may attenuate kidney susceptibility to the functional loss of end-stage kidney disease via IS. [ABSTRACT FROM AUTHOR]