Involvement of M3 cholinergic receptor signal transduction pathway in regulation of the expression of chemokine MOB-1, MCP-1 genes in pancreatic acinar cells

M3 receptor is involved in the effect of penehyclidine hydrochloride reduced endothelial injury in LPS-stimulated human pulmonary microvascular endothelial cell

LPS has been recently shown to induce muscarinic acetylcholine 3 receptor (M₃ receptor) expression and penehyclidine hydrochloride (PHC) is an anticholinergic drug which could block the expression of M₃ receptor. PHC has been demonstrated to perform protective effect on cell injury. This study is to investigate whether the effect of PHC on microvascular endothelial injury is related to its inhibition of M₃ receptor or not. HPMVECs were treated with specific M₃ receptor shRNA or PBS, and randomly divided into LPS group (A group), LPS+PHC group (B group), LPS + M₃ shRNA group (C group) and LPS + PHC + M₃ shRNA group (D group). Cells were collected at 60 min after LPS treatment to measure levels of LDH, endothelial permeability, TNF-α and IL-6 levels, NF-κB p65 activation, I-κB protein expression, p38MAPK, and ERK1/2 activations as well as M₃ mRNA expression. PHC could decrease LDH levels, cell permeability, TNF-α and IL-6 levels, p38 MAPK, ERK1/2, NF-κB p65 activations and M₃ mRNA expressions compared with LPS group. When M₃ receptor was silence, the changes of these indices were much more obvious. These findings suggest that M₃ receptor plays an important role in LPS-induced pulmonary microvascular endothelial injury, which is regulated through NF-κB p65 and MAPK activation. And knockout of M₃ receptor could attenuate LPS-induced pulmonary microvascular endothelial injury. Regulative effects of PHC on pulmonary microvascular permeability and NF-κB p65 as well as MAPK activations are including but not limited to inhibition of M₃ receptor.

Animal models of gastrointestinal and liver diseases. Animal models of acute and chronic pancreatitis

Animal models of pancreatitis are useful for elucidating the pathogenesis of pancreatitis and developing and testing novel interventions. In this review, we aim to summarize the most commonly used animal models, overview their pathophysiology, and discuss their strengths and limitations. We will also briefly describe common animal study procedures and refer readers to more detailed protocols in the literature. Although animal models include pigs, dogs, opossums, and other animals, we will mainly focus on rodent models because of their popularity. Autoimmune pancreatitis and genetically engineered animal models will be reviewed elsewhere.

Effect of M3 muscarinic acetylcholine receptor deficiency on collagen antibody-induced arthritis

BACKGROUND

There is increasing evidence that the non-neuronal cholinergic system might be of importance for the pathology of rheumatoid arthritis. The role of M3 muscarinic acetylcholine receptor (M3R) in this regard has, however, not been investigated to date. Thus, in the present study we analyzed if M3R deficiency might have a protective effect on experimentally induced arthritis.

METHODS

Collagen antibody-induced arthritis (CAIA) was evoked in M3R-deficient (M3R(-/-)) mice and wild-type (WT) littermates. Severity of arthritis was assessed by scoring of paw swelling. The joints of arthritic and nonarthritic animals were analyzed for histopathological changes regarding synovial tissue, cartilage degradation and bone destruction. Further, gene expression analysis of respective markers was performed. Systemic and local inflammatory response was determined by flow cytometry and immunohistochemistry for leukocytes as well as mRNA and protein measurements for pro-inflammatory cytokines and chemokines.

RESULTS

In arthritic M3R(-/-) mice the number of leukocytes, specifically neutrophils, was enhanced even though clinical arthritis score was not significantly different between WT and M3R(-/-) mice with CAIA. In M3R(-/-) mice, levels of neutrophil chemoattractant chemokine C-X-C-motif ligand 2 (CXCL2) as well as the pro-inflammatory cytokine interleukin-6 were already strongly increased in mice with low arthritis score, whereas WT mice only showed prominent expression of these markers when reaching high arthritis scores. Furthermore, arthritic M3R(-/-) mice displayed a stronger degradation of collagen II in the articular cartilage and, most strikingly, histopathological evaluation revealed more severe bone destruction in arthritic mice with M3R deficiency compared to WT littermates. Moreover, in M3R(-/-) mice, gene expression of markers for bone degradation (matrix metalloproteinase 13, cathepsin K and receptor activator of nuclear factor-κB ligand) was already increased in mice with low arthritis score.

CONCLUSIONS

Taken together, the present study shows that while M3R(-/-) mice were not protected from CAIA, they had a tendency toward a higher inflammatory response after arthritis induction than WT mice. Further, arthritis-induced joint destruction was significantly stronger in mice with M3R deficiency, indicating that stimulation of M3R might have protective effects on arthritis.

M3 subtype of muscarinic acetylcholine receptor promotes cardioprotection via the suppression of miR-376b-5p

The M₃ subtype of muscarinic acetylcholine receptors (M₃-mAChR) plays a protective role in myocardial ischemia and microRNAs (miRNAs) participate in many cardiac pathophysiological processes, including ischemia-induced cardiac injury. However, the role of miRNAs in M₃-mAChR mediated cardioprotection remains unexplored. The present study was designed to identify miRNAs that are involved in cardioprotective effects of M₃-mAChR against myocardial ischemia and elucidate the underlying mechanisms. We established rat model of myocardial ischemia and performed miRNA microarray analysis to identify miRNAs involved in the cardioprotection of M₃-mAChR. In H9c2 cells, the viability, intracellular free Ca²⁺ concentration ([Ca²⁺]i), intracellular reactive oxygen species (ROS), miR-376b-5p expression level, brain derived neurophic factor (BDNF) and nuclear factor kappa-B (NF-κB) levels were measured. Our results demonstrated that M₃-mAChR protected myocardial ischemia injury. Microarray analysis and qRT-PCR revealed that miR-376b-5p was significantly up-regulated in ischemic heart tissue and the M₃-mAChRs agonist choline reversed its up-regulation. In vitro, miR-376b-5p promoted H₂O₂-induced H9c2 cell injuries measured by cells viability, [Ca²⁺]i and ROS. Western blot and luciferase assay identified BDNF as a direct target of miR-376b-5p. M₃-mAChR activated NF-κB and thereby inhibited miR-376b-5p expression. Our data show that a novel M₃-mAChR/NF-κB/miR-376b-5p/BDNF axis plays an important role in modulating cardioprotection. MiR-376b-5p promotes myocardial ischemia injury possibly by inhibiting BDNF expression and M₃-mAChR provides cardioprotection at least partially mediated by the downregulation of miR-376b-5p through NF-κB. These findings provide new insight into the potential mechanism by which M₃-mAChR provides cardioprotection against myocardial ischemia injury.

Protein kinase D1 mediates NF-kappaB activation induced by cholecystokinin and cholinergic signaling in pancreatic acinar cells

The transcription factor NF-kappaB plays a critical role in inflammatory and cell death responses during acute pancreatitis. Previous studies in our laboratory demonstrated that protein kinase C (PKC) isoforms PKCdelta and epsilon are key regulators of NF-kappaB activation induced by cholecystokinin-8 (CCK-8), tumor necrosis factor-alpha, and ethanol. However, the downstream participants in regulating NF-kappaB activation in exocrine pancreas remain poorly understood. Here, we demonstrate that protein kinase D1 (PKD1) is a key downstream target of PKCdelta and PKCepsilon in pancreatic acinar cells stimulated by two major secretagogues, CCK-8 and the cholinergic agonist carbachol (CCh), and that PKD1 is necessary for NF-kappaB activation induced by CCK-8 and CCh. Both CCK-8 and CCh dose dependently induced a rapid and striking activation of PKD1 in rat pancreatic acinar cells, as measured by in vitro kinase assay and by phosphorylation at PKD1 activation loop (Ser744/748) or autophosphorylation site (Ser916). The phosphorylation and activation of PKD1 correlated with NF-kappaB activity stimulated by CCK-8 or CCh, as measured by NF-kappaB DNA binding. Either inhibition of PKCdelta or epsilon by isoform-specific inhibitory peptides, genetic deletion of PKCdelta and epsilon in pancreatic acinar cells, or knockdown of PKD1 by using small interfering RNAs in AR42J cells resulted in a marked decrease in PKD1 and NF-kappaB activation stimulated by CCK-8 or CCh. Conversely, overexpression of PKD1 resulted in augmentation of CCK-8- and CCh-stimulated NF-kappaB activation. Finally, the kinetics of PKD1 and NF-kappaB activation during cerulein-induced rat pancreatitis showed that both PKD1 and NF-kappaB activation were early events during acute pancreatitis and that their time courses of response were similar. Our results identify PKD1 as a novel early convergent point for PKCdelta and epsilon in the signaling pathways mediating NF-kappaB activation in pancreatitis.

Relationship between carbachol hyperstimulation-induced pancreatic acinar cellular injury and trypsinogen or NF-kappaB activation in rats in vitro

The relationship between M3 cholinergic receptor agonist (carbachol) hyperstimulation-induced pancreatic acinar cellular injury and trypsinogen activation or NF-kappaB activation in rats was studied in vitro. Rat pancreatic acinar cells were isolated, cultured and treated with carbachol, the active protease inhibitor (pefabloc), and NF-kappaB inhibitor (PDTC) in vitro. Intracellular trypsin activity was measured by using a fluorogenic substrate. The cellular injury was evaluated by measuring the leakage of LDH from pancreatic acinar cells. The results showed that as compared with control group, 10(-3) mol/L carbachol induced a significant increase of the intracellular trypsin activity and the leakage of LDH from pancreatic acinar cells. Pretreatment with 2 mmol/L pefabloc could significantly decrease the activity of trypsin and the leakage of LDH from pancreatic acinar cells (P < 0.01) following the treatment with a high concentration of carbachol (10(-3) mol/L) in vitro. The addition of 10(-2) mol/L PDTC didn't result in a significant decrease in the activity of trypsin and the leakage of LDH from pancreatic acinar cells treated with a high concentration of carbachol (10(-3) mol/L) in vitro (P > 0.05). It was concluded that intracellular trypsinogen activation is likely involved in pancreatic acinar cellular injury induced by carbachol hyperstimulation in vitro. NF-kappaB activation may not be involved in pancreatic acinar cellular injury induced by carbachol hyperstimulation in vitro.