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Macrophages are active contributors to the innate immune defense system. As macrophage activation is clearly affected by the surrounding microenvironment, the present study investigated the effect of sulforaphane (SFN) on the bactericidal activity of macrophages and the underlying molecular mechanisms involved in this process. Human THP‑1‑derived macrophages, primary human peripheral blood mononuclear cell‑derived macrophages, and primary mouse bone marrow derived‑macrophages (BMDMs) pretreated with SFN or DMSO were utilized in a model of Staphylococcus aureus infection. The results suggested that SFN pretreatment of macrophages effectively repressed the intracellular survival of S. aureus through modulation of p38/JNK signaling and decreased S. aureus‑induced caspases‑3/7‑dependent cell apoptosis, potentially through downregulation of microRNA (miR)‑142‑5p and miR‑146a‑5p. As SFN is a well‑known activator of nuclear factor erythroid 2‑related factor 2 (Nrf2), Nrf2‑/‑ BMDMs were used to demonstrate that the SFN‑mediated inhibitory effect was independent of Nrf2. Nevertheless, an increase in intracellular bacterial survival in Nrf2‑deficient macrophages was observed. In addition, SFN pretreatment suppressed S. aureus‑induced transcriptional expression of genes coding for the proinflammatory cytokines interleukin (IL)‑1β, IL‑6, and tumor necrosis factor‑α (TNF‑α), as well as for the M1 markers C‑C motif chemokine receptor 7, IL‑23 and inducible nitric oxide synthase (iNOS). Western blot analysis indicated that S. aureus challenge activated p38 mitogen‑activated protein kinase (MAPK) (p38) and c‑Jun N‑terminal kinase (JNK) MAPK signaling pathways, while SFN pretreatment prevented p38 and JNK phosphorylation. Pretreatment with 2 specific inhibitors of p38 and JNK, SB203580 and SP600125, respectively, resulted in a decrease in S. aureus‑induced proinflammatory gene expression levels compared with those observed in the SFN‑pretreated macrophages. Furthermore, THP‑1‑derived macrophages pretreated with SB203580 or SP600125 prior to bacterial infection exhibited a significant inhibition in intracellular S. aureus survival. In conclusion, we hypothesize that concomitant targeting of the p38/JNK‑inflammatory response and the S. aureus‑induced apoptosis with SFN may be a promising therapeutic approach in S. aureus infection.

With 4 billion people in lockdown in the world, COVID-19 outbreak may result in excessive sedentary time, especially in the population of vulnerable and disabled subjects. In many chronic disorders and diseases including type 2 diabetes mellitus and hypertension, cardiovascular and immune beneficial effects of exercise interventions should be reminded.

Repetitive transcranial magnetic stimulation (rTMS) is a promising, innovative, and non-invasive therapy used clinically. Efficacy of rTMS has been demonstrated to ameliorate psychiatric disorders and neuropathic pain through neuromodulation of affected neural circuits. However, little is known about the mechanisms and the specific neural circuits via which rTMS facilitates these functional effects. The aim of this study was to begin revealing the mechanisms by which rTMS may tap into existing neural circuits, by using a well characterized spinal motor circuit – the phrenic circuit. Here we hypothesized that rTMS can be used to enhance phrenic motoneuron excitability in anesthetized Sprague Dawley rats. Multiple acute rTMS protocols were used revealing 10 Hz rTMS protocol induced a robust, long-lasting increase in phrenic motoneuron excitability, functionally evaluated by diaphragm motor evoked potentials (59.1 ± 21.1 % of increase compared to baseline 60 min after 10 Hz protocol against 6.0 ± 5.8 % (p = 0.007) for Time Control, −5.8 ± 7.4 % (p < 0.001) for 3 Hz, and 5.2 ± 12.5 % (p = 0.008) for 30 Hz protocols). A deeper analyze allowed to discriminate “responder” and “non-responder” subgroups among 10 Hz rTMS treated animals. Intravenous injections of GABA(A) and GABA(B) receptor agonists prior to 10 Hz rTMS treatment, abolished the enhanced phrenic motoneuron excitability, suggesting GABAergic input plays a mechanistic role in rTMS-induced phrenic excitability. These data demonstrate that a single high frequency rTMS protocol at 10 Hz increases phrenic motoneuron excitability, mediated by a local GABAergic “disinhibition”. By understanding how rTMS can be used to affect neural circuits non-invasively we can begin to harness the therapeutic potential of this neuromodulatory strategy to promote recovery after disease or injury to the central nervous system.

Cervical spinal cord injury (SCI) results in permanent life-altering motor and respiratory deficits. Other than mechanical ventilation for respiratory insufficiency secondary to cervical SCI, effective treatments are lacking and the development of animal models to explore new therapeutic strategies are needed. The aim of this work was to demonstrate the feasibility of using a mouse model of partial cervical spinal hemisection at the second cervical metameric segment (C2) to investigate the impact of 6 weeks training on forced exercise wheel system on locomotor/respiratory plasticity muscles. To measure run capacity locomotor and respiratory functions, incremental exercise tests and diaphragmatic electromyography were done. In addition, muscle fiber type composition and capillary distribution were assessed at 51 days following chronic C2 injury in diaphragm, extensor digitorum communis (EDC), tibialis anterior (TA) and soleus (SOL) muscles. Six-week exercise training increased the running capacity of trained SCI mice. Fiber type composition in EDC, TA and SOL muscles was not modified by our protocol of exercise. The vascularization was increased in all muscle limbs in SCI trained group. No increase in diaphragmatic electromyography amplitude of the diaphragm muscle on the side of SCI was observed, while the contraction duration was significantly decreased in sedentary group compared to trained group. Cross-sectional area of type IIa myofiber in the contralateral diaphragm side of SCI was smaller in trained group. Fiber type distribution between contralateral and ipsilateral diaphragm in SCI sedentary group was affected, while no difference was observed in trained group. In addition, the vascularization of the diaphragm side contralateral to SCI was increased in trained group. All these results suggest an increase in fatigue resistance and a contribution to the running capacity in SCI trained group. Our exercise protocol could be a promising non-invasive strategy to sustain locomotor and respiratory muscle plasticity following SCI.

International audience; Inflammation plays a crucial role in the defense response of the innate immune system against pathogen infection. In this study, we selected 4 compounds for their potential or proven anti-inflammatory and/or anti-microbial properties to test on our in vitro model of bacteria-infected THP-1-derived macrophages. We first compared the capacity of sulforaphane (SFN), wogonin (WG), oltipraz (OTZ), and dimethyl fumarate (DMF) to induce the nuclear factor erythroid 2-related factor 2 (Nrf2), a key regulator of the antioxidant, anti-inflammatory response pathways. Next, we performed a comparative evaluation of the antioxidant and anti-inflammatory efficacies of the 4 selected compounds. THP-1-derived macrophages and LPS-stimulated macrophages were treated with each compound and expression levels of genes coding for inflammatory cytokines IL-1β, IL-6, and TNF-α were quantified by RT-qPCR. Moreover, expression levels of genes coding for M1 (IL-23, CCR7, IL-1β, IL-6, and TNF-α) and M2 (PPARγ, MRC1, CCL22, and IL-10) markers were determined in classically-activated M1 macrophages treated with each compound. Finally, the effects of each compound on the intracellular bacterial survival of gram-negative E. coli and gram-positive S. aureus in THP-1-derived macrophages and PBMC-derived macrophages were examined. Our data confirmed the anti-inflammatory and antioxidant effects of SFN, WG, and DMF on LPS-stimulated THP-1-derived macrophages. In addition, SFN or WG treatment of classically-activated THP-1-derived macrophages reduced expression levels of M1 marker genes, while SFN or DMF treatment upregulated the M2 marker gene MRC1. This decrease in expression of M1 marker genes may be correlated with the decrease in intracellular S. aureus load in SFN- or DMF-treated macrophages. Interestingly, an increase in intracellular survival of E. coli in SFN-treated THP-1-derived macrophages that was not observed in PBMC-derived macrophages. Conversely, OTZ exhibited pro-oxidant and proinflammatory properties, and affected intracellular survival of E. coli in THP-1-derived macrophages. Altogether, we provide new potential therapeutic alternatives in treating inflammation and bacterial infection.

International audience; High spinal cord injuries (SCI) lead to permanent respiratory insufficiency, and the search for new therapeutics to restore this function is essential. To date, the most documented preclinical model for high SCI is the rat cervical C2 hemisection. However, molecular studies with this SCI model are limited due to the poor availability of genetically modified specimens. The aim of this work was to evaluate the pathophysiology of respiratory activity following a cervical C2 injury at different times post-injury in a C57BL/6 mouse model. No significant spontaneous recovery of diaphragmatic activity was observed up to 30 days post-injury in eupneic condition. However, during a respiratory challenge, i.e. mild asphyxia, a partial restoration of the injured diaphragm was observed at 7 days post-injury, corresponding to the crossed phrenic phenomenon. Interestingly, the diaphragmatic recording between 2 respiratory bursts on the injured side showed an amplitude increase between 1–7 days post-injury, reflecting a change in phrenic motoneuronal excitability. This increase in inter-burst excitability returned to pre-injured values when the crossed phrenic phenomenon started to be effective at 7 days post-injury. Taken together, these results demonstrate the ability of the mouse respiratory system to express long-lasting plasticity following a C2 cervical hemisection and genetically modified animals can be used to study the pathophysiological effects on these plasticity phenomena.

Mycobacterium abscessusis a pathogenic, rapidly growing mycobacterium responsible for pulmonary and cutaneous infections in immunocompetent patients and in patients with Mendelian disorders, such as cystic fibrosis (CF).Mycobacterium abscessusis known to transition from a smooth (S) morphotype with cell surface-associated glycopeptidolipids (GPL) to a rough (R) morphotype lacking GPL. Herein, we show thatM. abscessusS and R variants are able to grow inside macrophages and are present in morphologically distinct phagosomes. The S forms are found mostly as single bacteria within phagosomes characterized by a tightly apposed phagosomal membrane and the presence of an electron translucent zone (ETZ) surrounding the bacilli. By contrast, infection with the R form leads to phagosomes often containing more than two bacilli, surrounded by a loose phagosomal membrane and lacking the ETZ. In contrast to the R variant, the S variant is capable of restricting intraphagosomal acidification and induces less apoptosis and autophagy. Importantly, the membrane of phagosomes enclosing the S forms showed signs of alteration, such as breaks or partial degradation. Although not frequently encountered, these events suggest that the S form is capable of provoking phagosome–cytosol communication. In conclusion,M. abscessusS exhibits traits inside macrophages that are reminiscent of slow-growing mycobacterial species.

High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model of respiratory insufficiency in adult rats is the C2 partial injury which causes unilateral diaphragm paralysis. This model allows the investigation of a particular population of respiratory bulbospinal axons which cross the midline at C3-C6 spinal segment, namely the crossed phrenic pathway. Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to study supraspinal descending respiratory pathways in the rat. Interestingly, a lateral C2 injury does not affect the amplitude and latency of the largest motor-evoked potential recorded from the diaphragm (MEPdia) ipsilateral to the injury in response to a single TMS pulse, compared to a sham animal. Although the rhythmic respiratory activity on the contralateral diaphragm is preserved at 7 days post-injury, no diaphragm activity can be recorded on the injured side. However, a profound reorganization of the MEPdia evoked by TMS can be observed. The MEPdia is reduced on the non-injured rather than the injured side. This suggests an increase in ipsilateral phrenic motoneurons excitability. Moreover, correlations between MEPdia amplitude and spontaneous contralateral diaphragmatic activity were observed. The larger diaphragm activity correlated with a larger MEPdia on the injured side, and a smaller MEPdia on the non-injured side. This suggests, for the first time, the occurrence of a functional neuroplasticity process involving changes in motoneuron excitability balance between the injured and non-injured sides at a short post-lesional delay.

Keratin 19 is a member of the cytokeratin family that is critical for maintenance of cellular architecture and organization, especially of epithelia. The pancreas has three distinct cell types, ductal, acinar, and islet, each with different functions. Embryologically, the pancreatic and duodenal homeobox 1 (PDX1) homeodomain protein is critical for the initiation of all pancreatic lineages; however, the later differentiation of the endocrine pancreas is uniquely dependent upon high PDX1 expression, whereas PDX1 is down-regulated in the ductal and acinar cell lineages. We find that this down-regulation may be required for normal ductal expression of cytokeratin K19. The K19 promoter-reporter gene assay demonstrates that ectopic PDX1 inhibits K19 reporter gene activity in primary pancreatic ductal cells. This is reinforced by our findings that retrovirally mediated stable transduction of PDX1 in primary pancreatic ductal cells suppresses K19 expression, and short interfering RNA to PDX1 in Min6 insulinoma cells results in the induction of normally undetectable K19. Complementary functional and biochemical approaches led to the unexpected finding that a multimeric complex of PDX1 and two members of the TALE homeodomain factor family, MEIS1a and PBX1b, regulates K19 gene transcription through a specific cis-regulatory element (-341 to -325) upstream of the K19 transcription start site. These data suggest a unifying mechanism whereby PDX1, myeloid ecotropic viral insertion site (MEIS), and pre-B-cell leukemia transcription factor 1 (PBX) may regulate ductal and acinar lineage specification during pancreatic development. Specifically, concomitant PDX1 suppression and MEIS isoform expression result in proper ductal and acinar lineage specification. Furthermore, PDX1 may inhibit the ductal differentiation program in the pancreatic endocrine compartment, particularly beta cells.

The genetic basis of pancreatic ductal adenocarcinoma, which constitutes the most common type of pancreatic malignancy, involves the sequential activation of oncogenes and inactivation of tumor suppressor genes. Among the pivotal genetic alterations are Ki-RAS oncogene activation and p53 tumor suppressor gene inactivation. We explain that the combination of these genetic events facilitates pancreatic carcinogenesis as revealed in novel three-dimensional cell (spheroid cyst) culture and in vivo subcutaneous and orthotopic xenotransplantation models. N-cadherin, a member of the classic cadherins important in the regulation of cell-cell adhesion, is induced in the presence of Ki-RAS mutation but subsequently downregulated with the acquisition of p53 mutation as revealed by gene microarrays and corroborated by reverse transcription-PCR and Western blotting. N-cadherin modulates the capacity of pancreatic ductal cells to migrate and invade, in part via complex formation with keratinocyte growth factor receptor and neural cell adhesion molecule and in part via interaction with p120-catenin. However, modulation of these complexes by Ki-RAS and p53 leads to enhanced cell migration and invasion. This preferentially induces the downstream effector AKT over mitogen-activated protein kinase to execute changes in cellular behavior. Thus, we are able to define molecules that in part are directly affected by Ki-RAS and p53 during pancreatic ductal carcinogenesis, and this provides a platform for potential new molecularly based therapeutic interventions.

SummaryTo define the genetic requirements for pancreatic ductal adenocarcinoma (PDA), we have targeted concomitant endogenous expression of Trp53R172H and KrasG12D to the mouse pancreas, revealing the cooperative development of invasive and widely metastatic carcinoma that recapitulates the human disease. The primary carcinomas and metastases demonstrate a high degree of genomic instability manifested by nonreciprocal translocations without obvious telomere erosion—hallmarks of human carcinomas not typically observed in mice. No mutations were discovered in other cardinal tumor suppressor gene pathways, which, together with previous results, suggests that there are distinct genetic pathways to PDA with different biological behaviors. These findings have clear implications for understanding mechanisms of disease pathogenesis, and for the development of detection and targeted treatment strategies.

A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distress. To date, no efficient therapeutics have been developed to improve/ameliorate the respiratory failure following high cervical spinal cord injury (SCI). Here we propose a murine pre-clinical model of high SCI at the cervical 2 (C2) metameric level to study diverse post-lesional respiratory neuroplasticity. The technique consists of a surgical partial injury at the C2 level, which will induce a hemiparalysis of the diaphragm due to a deafferentation of the phrenic motoneurons from the respiratory centers located in the brainstem. The contralateral side of the injury remains intact and allows the animal recovery. Unlike other SCIs which affect the locomotor function (at the thoracic and lumbar level), the respiratory function does not require animal motivation and the quantification of the deficit/recovery can be easily performed (diaphragm and phrenic nerve recordings, whole body ventilation). This pre-clinical C2 SCI model is a powerful, useful, and reliable pre-clinical model to study various respiratory and non-respiratory neuroplasticity events at different levels (molecular to physiology) and to test diverse putative therapeutic strategies which might improve the respiration in SCI patients.

Respiratory related diseases associated with the neuronal control of breathing represent life-threatening issues and to date, no effective therapeutics are available to enhance the impaired function. The aim of this study was to determine whether a preclinical respiratory model could be used for further studies to develop a non-invasive therapeutic tool applied to rat diaphragmatic neuronal circuitry. Transcranial magnetic stimulation (TMS) was performed on adult male Sprague-Dawley rats using a human figure-of-eight coil. The largest diaphragmatic motor evoked potentials (MEPdia) were recorded when the center of the coil was positioned 6 mm caudal from Bregma, involving a stimulation of respiratory supraspinal pathways. Magnetic shielding of the coil with mu metal reduced magnetic field intensities and improved focality with increased motor threshold and lower amplitude recruitment curve. Moreover, transynaptic neuroanatomical tracing with pseudorabies virus (applied to the diaphragm) suggest that connections exist between the motor cortex, the periaqueductal grey cell regions, several brainstem neurons and spinal phrenic motoneurons (distributed in the C3-4 spinal cord). These results reveal the anatomical substrate through which supraspinal stimulation can convey descending action potential volleys to the spinal motoneurons (directly or indirectly). We conclude that MEPdia following a single pulse of TMS can be successfully recorded in the rat and may be used in the assessment of respiratory supraspinal plasticity. Supraspinal non-invasive stimulations aimed to neuromodulate respiratory circuitry will enable new avenues of research into neuroplasticity and the development of therapies for respiratory dysfunction associated with neural injury and disease (e.g. spinal cord injury, amyotrophic lateral sclerosis).

Cell adhesion can be divided into cell-cell adhesion mediated by three major structures, tight junctions, adherens junctions, desmosomes, and cell-matrix adhesion, which is for the most part integrin-based. Cell-cell interactions play an important role in the maintenance and integrity of tissues and organs but similar to cell-matrix complexes may also transduce cell signaling. While this is the basics for understanding cell adhesion and its function, the role of cell adhesion proteins in disease, especially tumorigenesis, is far more diverse. A summary is given in the paper presented by Dr. Andl in this issue where she also focuses on recently discovered cell adhesion components and the regulation of cell adhesion molecules by miRNAs. In cancer, cell adhesion molecules are generally thought to be deactivated in order to aid in cancer cell dissemination and dispersal. However, aside from the loss of function, various gain-of-function events occur during induction and progression of cancer that can be mediated by cell adhesion molecules. Many of the molecules involved in these processes, such as the components of desmosomes, were initially identified as targets of autoimmune diseases. This special issue outlines the latest findings in research and review articles. Tight junctions mediate apical cell-cell adhesion and regulate epithelial cell polarity. Members of the claudin family are involved in a number of diseases including cancer; however, little is known regarding the mechanisms behind their pathophysiological function. Drs. Singh, Sharma, and Dhawan give an overview of the current state of knowledge in this issue. To identify cell transformation mechanisms other than previously described, Lynch et al. investigated the effect of MMP-7 mediated cleavage of E-cadherin. They demonstrate that loss of cell-cell adhesion is induced following E-cadherin processing, which results in increased cell migration, loss of polarization, and activation of RhoA. Interactions of cell adhesion molecules with their environment are central to their regulation and to cell migration and invasion. In the tumor context, the array of integrin receptors expressed causes the cells to differentially respond to external signals, resist the effects of cytotoxic drugs, and facilitate growth and invasion through a range of different tissue environments encountered by invasive cancer cells. In particular, the regulation of integrin receptor interaction with the extracellular matrix is thought to be critical for those cancers that invade and metastasize using a mesenchymal mode of migration. Jossen et al. show a novel prostate cancer bone metastatic model to assay drug sensitivity in three-dimensional cultures that mimic the preclinical or clinical setting more accurately. In here, they show that prostate cells revert to more epithelial cells, mesenchymal-epithelial transition (MET) in the presence of bone stroma modeling later stages of metastatic colonization, and are sensitized to radiation treatment when blocking E-cadherin or α-integrin. Mesenchymal migration as a therapeutic target for glioblastoma is discussed by Zhong et al. Another potential therapeutic agent, a Src inhibitor, is described by Yaseem et al. Comparison of SKI-606 and Iressa effects, Src/Abl and EGFR inhibitors, respectively, on cervical cancer cell lines shows inhibition of cell proliferation. Additionally, SKI-606 decreases cell migration and invasion through MET accompanied by the re-expression of E-cadherin and the recruitment of β-catenin to the cell membrane. Hironobu Yamashita et al. demonstrate that lysophosphatidic acid, a phospholipid growth factor, induces the stimulation of lamellipodia formation and enhanced cell migration through the upregulation of the TGFβ1 target gene Laminin-322. The role of focal adhesion kinase (FAK) phosphorylation in the dynamic regulation of integrin-based adhesions and cellular migration is shown in a paper by Hamadi et al. Upon pervanadate-induced phosphorylation, FAK delocalizes from focal adhesions to newly formed membrane ruffles in a src-dependent event. Finally, advances in nanotechnology that allow the study of cellular transformation in engineered cellular environments are introduced by Siti Hawa Ngalmi et al. Such cross-disciplinary approaches have begun to advance our knowledge of how adhesion signaling is organized and how cells relay information regarding the composition and structure of the external environment into biological activity. In particular, these advances are being driven by novel microscopy technologies and the continuing development of new techniques that allow us to visualize the intricate workings of adhesion-dependent signaling processes. This synopsis gives a glimpse at the current leading edge science published in this special issue of the Journal of Oncology. We hope that these papers inspire interest in multidisciplinary approaches as well as in the identification of novel therapeutics. Claudia D. Andl Ala-Eddin Al Moustafa Therese B. Deramaudt Geraldine M. O'Neill

Pancreatic ductal adenocarcinoma (PDA) is an extremely aggressive malignancy, which carries a dismal prognosis. Activating mutations of the Kras gene are common to the vast majority of human PDA. In addition, recent studies have demonstrated that embryonic signaling pathway such as Hedgehog and Notch are inappropriately upregulated in this disease. The role of another embryonic signaling pathway, namely the canonical Wnt cascade, is still controversial. Here, we use gene array analysis as a platform to demonstrate general activation of the canonical arm of the Wnt pathway in human PDA. Furthermore, we provide evidence for Wnt activation in mouse models of pancreatic cancer. Our results also indicate that Wnt signaling might be activated downstream of Hedgehog signaling, which is an early event in PDA evolution. Wnt inhibition blocked proliferation and induced apoptosis of cultured adenocarcinoma cells, thereby providing evidence to support the development of novel therapeutical strategies for Wnt inhibition in pancreatic adenocarcinoma.

In a recent issue of Cell Death and Discovery, we described a new mechanism by which sulforaphane decreased mycobacterial burden in an in vitro model of THP-1-derived macrophage infection by Mycobacterium abscessus.1 This sulforaphane-mediated diminution was due to the induction of a caspase-independent cell apoptosis and necessitated activation of both nuclear factor E2-related factor 2 (Nrf2) and p38 mitogen-activated protein kinases (MAPK) signaling pathways. M. abscessus is a nontuberculous mycobacterium that belongs to the group of rapid growing mycobacteria. This emerging pathogen is able to cause skin, bone and soft tissue infections, and more generally exacerbations of lung diseases.2 Its high tolerance to antibiotics, which limits patient treatment, has become a public health concern worldwide. M. abscessus has been increasingly involved in patients with cystic fibrosis and in immunosuppressed patients,3 enhancing their risk of developing chronic airway infections and leading to a fatal outcome. Bacterial infection induces an imbalance between oxidants and antioxidants, triggering an oxidative burst that is well known for its bactericidal effect. Yet, some selected mycobacteria are able to thrive in this oxidative environment. It is then unsurprising that the use of oxidant scavengers such as MnTE-2-PyP or N-acetyl-L-cysteine has been shown to decrease M. abscessus load by activating bacterial killing in phagolysosomes.4 In our study, we decreased the oxidative environment in THP-1-derived macrophages by activating Nrf2, the key transcription factor that controls the cascade of cytoprotective and antioxidant defense mechanisms, and the maintenance of the redox homeostasis. Upon oxidative stress or infection, cytoplasmic Nrf2 is released from its inhibitor Keap-1, translocates into the nucleus, and forms a cofactor complex that binds to specific antioxidant responsive elements (ARE) found in promoters of phase II antioxidant and detoxifying enzymes. Nrf2 signaling pathway has been shown to have an important role whether beneficial or detrimental, in microbial infections.5 M. abscessus infection of THP-1-derived macrophages activates Nrf2 signaling pathway, and induces the expression of heme oxygenase-1 and NADPH quinone oxidoreductase-1, two downstream targets of Nrf2. In addition, M. abscessus induced reactive oxygen species (ROS) production in infected macrophages and blocked phagosomal acidification thus allowing its intracellular proliferation. Sulforaphane, a well-established activator of Nrf2 was used to pretreat macrophages before mycobacterial infection. The results showed an inhibition of mycobacterial growth 7 days postinfection in sulforaphane pretreated macrophages compared with vehicle pretreated ones. This sulforaphane-induced mycobacterial growth inhibition was neither caused by phagosomal pH acidification nor increase in cell phagocytosis, but rather induction of cell apoptosis. Contrary to the well-known cyprotective effect of sulforaphane and Nrf2 signaling pathway,6 we demonstrated that pre-stimulation of Nrf2 signaling pathway by sulforaphane before M. abscessus infection triggered a caspase-independent cell apoptosis. Pretreatment of macrophages with sulforaphane alone had no significant effect on cell death. To our knowledge, this is the first study showing sulforaphane-induced Nrf2 triggers a caspase3/7-independent and p38 MAPK-dependent cell apoptosis in mycobacteria infected macrophages (Figure 1). Figure 1 Infection of THP-1 derived macrophages by M. abscessus elicits caspase3/7-dependent cell apoptosis. Pretreatment of macrophages with an Nrf2 activator before mycobacterial challenge initiates a caspase-independent cell apoptosis Cell death in macrophages has a critical role in the host response to mycobacterial infection. Cell apoptosis is an effective mechanism used by the innate defense system to fight bacterial infection. This energy-dependent mechanism generates apoptotic bodies that will facilitate T-dependent antigen response and induce mycobacterial killing by uninfected neighboring macrophages.7 As M. abscessus has only been recently identified as a separate species, very little is known in the dynamics between M. abscessus and macrophage cell survival/cell death. In our in vitro model, M. abscessus induced cell necrosis in untreated cells but not cell apoptosis. This phenomenon has been observed in M. tuberculosis that has the ability to inhibit cell apoptosis in favor of cell necrosis.8 Recent highlights on caspase-independent forms of apoptosis triggered by infection have been described in the literature. Necroptosis, also known as programmed necrosis, can be initiated by various agents including microbial infection, and is characterized by activation of the receptor-interacting protein (RIP) kinases RIP1 and RIP3-dependent signaling pathway. This programmed cell death is a critical antiviral process in the host innate immune defense system. Phagocytes infected with viruses that are able to inhibit the classical caspase-dependent apoptosis pathway can undergo necroptosis to facilitate viral clearance by the neighboring immune system.9, 10 Moreover, Roca and Ramakrishnan have demonstrated a tumor-necrosis factor (TNF)-induced necroptosis in a M. tuberculosis infected zebrafish model. In the early stages of mycobacteria infection, injection of an excess of TNF in infected macrophages induced mitochondrial ROS production through a RIP1/RIP3-dependent kinase pathway, process necessary for the bacterial clearance. However, ROS-mediated necroptosis rapidly led to release and propagation of M. tuberculosis in the extracellular microenvironment.11 Another caspase 3/7-independent apoptosis is the inflammation-mediated cell death known as pyroptosis. This particular programmed cell death participates in the host cell defense system against pathogens and requires activation of caspase 1, IL-1β and IL-18.12 Recently, Bai et al.13 have shown that M. tuberculosis-mediated production of IL-32γ in THP-1-derived macrophages induced caspase 1-dependent pyroptosis which help reduce intracellular M. tuberculosis burden. In conclusion, additional studies are required to specifically identify the caspase-independent form(s) of apoptosis initiated by the combination of Nrf2 activation and M. abscessus infection. Nevertheless, our findings strongly suggest that Nrf2 activators may be of great interest as future therapeutic treatments in supplement to the actual lengthy multi-drug therapies used in patients diagnosed with mycobacterial infection.

Background & Aims: The Ki-RAS oncogene is altered in pancreatic ductal neoplasms. Pancreatic ductal cells (PDCs) were purified from cytokeratin 19 (K19)- Ki-RAS G12V transgenic mice and control littermates to identify properties of Ki-Ras activation in a cell-type-specific context. Because Ki-RAS mutation has prognostic significance in patients treated with radiation, we studied the influence of Ki-RAS status on radiation survival. Methods: Pancreatic ductal fragments from mice with Ki-RAS G12V mutation or wild-type (WT)- Ki-RAS were cultured. Growth curves, electron microscopy, flow cytometry, and analysis of signaling and cell-cycle proteins were established. Farnesyltransferase inhibitor (FTI) treatment with R115777 before and after irradiation was used to determine the effect of Ki-Ras farnesylation on cell survival. Results: PDCs from WT and K19-Ki-RAS G12V mice had features of ductal cells with formation of 3-dimensional structures on collagen without differences in morphology, growth, and cell-cycle distribution. This may result from up-regulation of p16INK4 and p27 Kip1 and lack of hyperstimulation of the mitogen-activated protein kinase pathway in Ki-RAS G12V PDCs. No differences in radiation survival between Ki-RAS G12V PDCs and WT PDCs were observed. However, Ki-RAS G12V PDCs expressing mutant p53 V143A had enhanced survival compared with WT PDCs transduced with p53 V143A . R115777 treatment sensitized Ki-RAS G12V PDCs and Ki-RAS G12V /p53 V143A PDCs, but not WT PDCs. Conclusions: Novel characterization of murine WT PDCs and Ki-RAS G12V PDCs is described. Induction of cell-cycle regulators and lack of mitogen-activated protein kinase hyperstimulation likely are responsible for constraining activated Ki-RAS G12V -mediated proliferation. Because its activation was required for sensitization by an FTI, R115777 may be useful against pancreatic tumors expressing oncogenic Ki-Ras.

A frequent genetic alteration found in premalignant stages of pancreatic adenocarcinoma is K-ras oncogene point mutation. The mechanistic basis for the inability of K-ras mutation to transform pancreatic ductal cells is unclear, although cooperating events with p16 inactivation, p53 mutation, and SMAD 4 mutation are recognized to be necessary. We have generated a novel mouse model in which the cytokeratin 19 promoter, specifically active in pancreatic ductal cells but not other cell types of the pancreas, is fused to mutant K-ras. This is of direct relevance to human pancreatic cancer because premalignant lesions are found specifically in ductal cells. There is dramatic periductal lymphocytic infiltration in the pancreata of transgenic mice, predominantly CD4+ T lymphocytes, which may act as an adaptive immune response to activated ras-mediated signaling. In addition, gene array analysis reveals an induction of N-cadherin in transgenic mice pancreatic ductal cells, the significance of which relates to promotion of cell adhesion and deterrence of cell migration. Apart from these important biological considerations, there is parallel activity of the cytokeratin 19 promoter in the stem cell region of the gastric epithelium, namely in mucous neck cells. Activated K-ras in this context causes mucous neck cell hyperplasia, a precursor to gastric adenocarcinoma. There is concomitant parietal cell decrease, which is a key step toward gastric adenocarcinoma. Taken together, we have defined how mutant K-ras signaling modulates important molecular events in the initiating events of pancreatic and gastric carcinogenesis.