Receptor tyrosine and MAP kinase are involved in effects of H(2)O(2) on interstitial cells of Cajal in murine intestine

Effects of Bifidobacterium lactis BLa80 on fecal and mucosal flora and stem cell factor/c-kit signaling pathway in simulated microgravity rats

BACKGROUND

Simulated microgravity environment can lead to gastrointestinal motility disturbance. The pathogenesis of gastrointestinal motility disorders is closely related to the stem cell factor (SCF)/c-kit signaling pathway associated with intestinal flora and Cajal stromal cells. Moreover, intestinal flora can also affect the regulation of SCF/c-kit signaling pathway, thus affecting the expression of Cajal stromal cells. Cajal cells are the pacemakers of gastrointestinal motility.

AIM

To investigate the effects of Bifidobacterium lactis (B. lactis) BLa80 on the intestinal flora of rats in simulated microgravity and on the gastrointestinal motility-related SCF/c-kit pathway.

METHODS

The internationally recognized tail suspension animal model was used to simulate the microgravity environment, and 30 rats were randomly divided into control group, tail suspension group and drug administration tail suspension group with 10 rats in each group for a total of 28 days. The tail group was given B. lactis BLa80 by intragastric administration, and the other two groups were given water intragastric administration, the concentration of intragastric administration was 0.1 g/mL, and each rat was 1 mL/day. Hematoxylin & eosin staining was used to observe the histopathological changes in each segment of the intestine of each group, and the expression levels of SCF, c-kit, extracellular signal-regulated kinase (ERK) and p-ERK in the gastric antrum of each group were detected by Western blotting and PCR. The fecal flora and mucosal flora of rats in each group were detected by 16S rRNA.

RESULTS

Simulated microgravity resulted in severe exfoliation of villi of duodenum, jejunum and ileum in rats, marked damage, increased space between villi, loose arrangement, shortened columnar epithelium of colon, less folds, narrower mucosal thickness, reduced goblet cell number and crypts, and significant improvement after probiotic intervention. Simulated microgravity reduced the expressions of SCF and c-kit, and increased the expressions of ERK and P-ERK in the gastric antrum of rats. However, after probiotic intervention, the expressions of SCF and c-kit were increased, while the expressions of ERK and P-ERK were decreased, with statistical significance (P < 0.05). In addition, simulated microgravity can reduce the operational taxonomic unit (OTU) of the overall intestinal flora of rats, B. lactis BLa80 can increase the OTU of rats, simulated microgravity can reduce the overall richness and diversity of stool flora of rats, increase the abundance of firmicutes in stool flora of rats, and reduce the abundance of Bacteroides in stool flora of rats, most of which are mainly beneficial bacteria. Simulated microgravity can increase the overall richness and diversity of mucosal flora, increase the abundance of Bacteroides and Desulphurides in the rat mucosal flora, and decrease the abundance of firmicutes, most of which are proteobacteria. After probiotics intervention, the overall Bacteroidetes trend in simulated microgravity rats was increased.

CONCLUSION

B. lactis BLa80 can ameliorate intestinal mucosal injury, regulate intestinal flora, inhibit ERK expression, and activate the SCF/c-kit signaling pathway, which may have a facilitating effect on gastrointestinal motility in simulated microgravity rats.

Spontaneous electrical activity of cultured interstitial cells of cajal from mouse urinary bladder

Interstitial cells of Cajal (ICCs) from the urinary bladder regulate detrusor smooth muscle activities. We cultured ICCs from the urinary bladder of mice and performed patch clamp and intracellular Ca²⁺ ([Ca²⁺]_i) imaging to investigate whether cultured ICCs can be a valuable tool for cellular functional studies. The cultured ICCs displayed two types of spontaneous electrical activities which are similar to those recorded in intact bladder tissues. Spontaneous electrical activities of cultured ICCs were nifedipine-sensitive. Carbachol and ATP, both excitatory neurotransmitters in the urinary bladder, depolarized the membrane and increased the frequency of spike potentials. Carbachol increased [Ca²⁺]_i oscillations and basal Ca²⁺ levels, which were blocked by atropine. These results suggest that cultured ICCs from the urinary bladder retain rhythmic phenotypes similar to the spontaneous electrical activities recorded from the intact urinary bladder. Therefore, we suggest that cultured ICCs from the urinary bladder may be useful for cellular and molecular studies of ICCs.

Inhibition of pacemaker activity in interstitial cells of Cajal by LPS via NF-κB and MAP kinase

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.

Effects of sphingosine-1-phosphate on pacemaker activity of interstitial cells of Cajal from mouse small intestine

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.

Biophysically based modeling of the interstitial cells of cajal: current status and future perspectives

Gastrointestinal motility research is progressing rapidly, leading to significant advances in the last 15 years in understanding the cellular mechanisms underlying motility, following the discovery of the central role played by the interstitial cells of Cajal (ICC). As experimental knowledge of ICC physiology has expanded, biophysically based modeling has become a valuable tool for integrating experimental data, for testing hypotheses on ICC pacemaker mechanisms, and for applications in in silico studies including in multiscale models. This review is focused on the cellular electrophysiology of ICC. Recent evidence from both experimental and modeling domains have called aspects of the existing pacemaker theories into question. Therefore, current experimental knowledge of ICC pacemaker mechanisms is examined in depth, and current theories of ICC pacemaking are evaluated and further developed. Existing biophysically based ICC models and their physiological foundations are then critiqued in light of the recent advances in experimental knowledge, and opportunities to improve these models are identified. The review concludes by examining several potential clinical applications of biophysically based ICC modeling from the subcellular through to the organ level, including ion channelopathies and ICC network degradation.

Interferon-γ plays a role in paraquat-induced neurodegeneration involving oxidative and proinflammatory pathways

Exposure to environmental contaminants, particularly pesticides, may be an important etiological factor in Parkinson's disease (PD); and evidence suggests a role for microglia-dependent inflammatory and oxidative processes in nigrostriatal pathology induced by such toxins. Yet, the events mediating microglial activation and their effects are not fully known. To this end, we hypothesized that the proinflammatory cytokine, interferon-gamma (IFN-γ), may be a prime factor in the pathogenesis of PD, given its critical role in regulating microglial responses to pathogens. Indeed, the present investigation demonstrated that genetic deletion of IFN-γ protected substantia nigra pars compacta (SNc) dopamine (DA) neurons from the toxic effects of the pesticide, paraquat, and normalized changes in inflammatory and oxidative factors within this brain region. Specifically, IFN-γ knockout prevented the paraquat-induced morphological signs of microglial activation and expression of key nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, while also preventing time-dependent changes in proinflammatory enzymes (inducible nitric oxide synthase [iNOS], cyclooxygenase-2 [COX-2]), cytokines (interleukin-1β [IL-1β], tumor necrosis factor-α [TNF-α]), and signaling factors (c-Jun N-terminal kinase [JNK], p38 MAP kinase [p38], Signal transducer and activator of transcription-1 [STAT1], nuclear factor kappa B [NF-κB]). Moreover, paraquat transiently suppressed substantia nigra pars compacta expression of trophic and proneuroplastic factors (cyclic-AMP response element binding protein [CREB], brain-derived neurotrophic factor [BDNF]), and IFN-γ deficiency again reversed these effects. These data suggest that IFN-γ is important for paraquat-induced neurodegeneration and the accompanying oxidative, inflammatory, and trophic changes that characterize the response to the toxin. Targeting IFN-γ could thus have therapeutic implications for PD and other neurodegenerative conditions that involve multiple inflammatory pathways.