The gastrointestinal (GI) tract is a vital organ that digests food, absorbs nutrients, and excretes waste. Normal GI motility is the basis for these functions. The interstitial cells of Cajal (ICC) in the GI muscularis layer promote GI motility together with the enteric nervous system and smooth muscle cells. Since GI motility results from complex coordination of these heterogeneous cells, failure of any one of them can lead to GI dysmotility. Knowledge about ICC in physiological conditions has accumulated in recent decades, while the pathophysiology of ICC in GI inflammatory diseases, such as inflammatory bowel disease, is not well understood. In this review, we summarize the previous studies about the pathophysiological changes of ICC in inflammatory diseases and discuss the inflammatory mediators that induce ICC dysfunction.

Esophageal achalasia is classified into three subtypes according to manometric findings. Since several factors, including clinical characteristics and treatment response, have been reported to differ among the subtypes, the underlying pathogenesis may also differ. However, a comprehensive understanding regarding the differences is still lacking. We therefore performed a systematic review of the differences among the three subtypes of achalasia to clarify the current level of comprehension. In terms of clinical features, type III, which is the least frequently diagnosed of the three subtypes, showed the oldest age and most severe symptoms, such as chest pain. In contrast, type I showed a higher prevalence of lung complications, and type II showed weight loss more frequently than the other types. Histopathologically, type I showed a high loss of ganglion cells in esophagus, and on a molecular basis, type III had elevated serum pro-inflammatory cytokine levels. In addition to peristalsis and the lower esophageal sphincter (LES) function, the upper esophageal sphincter (UES) function of achalasia has attracted attention, as an impaired UES function is associated with severe aspiration pneumonia, a fatal complication of achalasia. Previous studies have indicated that type II shows a higher UES pressure than the other subtypes, while an earlier decline in the UES function has been confirmed in type I. Differences in the treatment response are also crucial for managing achalasia patients. A number of studies have reported better responses in type II cases and less favorable responses in type III cases to pneumatic dilatation. These differences help shed light on the pathogenesis of achalasia and support its clinical management according to the subtype.

Distinct sex differences in the prevalence and symptoms of abnormal bowel habits in patients with irritable bowel syndrome (IBS) have been reported. We have elucidated the sex differences in the regulation of colorectal motility via the central nervous system. Noxious stimuli in the colorectum of anesthetized male rats enhance colorectal motility by activating monoaminergic neurons in descending pain inhibitory pathways from the brainstem to the lumbosacral spinal cord. These monoaminergic neurons release serotonin and dopamine into the lumbosacral spinal cord, resulting in the increment of colorectal motility. In female rats, in contrast, noxious stimuli in the colorectum have no effect on colorectal motility. We clarified that GABAergic inhibition in the lumbosacral spinal cord masks the enhancement of colorectal motility induced by monoamines in female animals. Considering that IBS patients often show visceral hypersensitivity and hyperalgesia, our studies suggest that differences in the descending neurons that respond to painful stimuli are involved in various sex differences in abnormal bowel habits.

Garcinia buchananii stem bark extract (GBB), commonly used for treating diarrhea in Africa, triggers ectopic aboral contractions, causing inhibition of propulsive motility in the colon ex vivo. To determine whether or not these effects were associated with decreased inhibitory neuromuscular transmission, the responsible constituent compounds, and mechanisms of action, we studied the effects of GBB and specific fractions and flavanones isolated from GBB on intestinal motility using pellet propulsion assays in guinea pig distal colons. In addition, microelectrode recordings were used to measure the effects on the inhibitory junction potentials (IJPs) in the porcine ileum and descending colon smooth muscle. Psychoactive Drug Screening Program secondary receptor functional assays were used to determine whether or not GBB and its constituent compounds act via purinergic (P2Y) and muscarinic receptors. GBB inhibited propulsive motility, but (2R,3S,2″R,3″R)-manniflavanone (MNF), (2R,3S,2″R,3″R)-GB-2 (GB-2) and (2R,3S,2″S)-buchananiflavanone (BNF), the main ingredients of GBB, did not affect motility. We discovered that, in the porcine descending colon, IJPs contained purinergic, nitrergic, and nonpurinergic nonnitrergic components. Furthermore, ileal IJPs were purely purinergic. GBB blocked all components of IJPs, while MNF and GB-2 inhibited purinergic IJPs only. BNF inhibited the purinergic and nonpurinergic components of IJPs. MRS2365, a Y1 (P2Y) agonist, did not evoke sustained membrane hyperpolarization in the presence of GBB. However, GBB, MNF, GB-2 and BNF did not affect P2Y or muscarinic receptors. In conclusion, inhibitory neuromuscular transmission in the porcine descending colon involves all components of IJPs. GBB decreases inhibitory neuromuscular transmission, likely by the actions of MNF, GB-2 and BNF. These effects do not involve P2Y or muscarinic receptors.

Vascular smooth muscle cell (VSMC) migration plays an important role in cardiovascular diseases, including atherosclerotic plaque formation and restenosis after vascular intervention. The mechanisms involved in VSMC migration are complex and have not been fully elucidated. Recently, we discovered a novel interaction, direct binding of active Fyn-paxillin at focal adhesions, which plays an important role in actin stress fiber formation and migration in VSMCs. In this review, we highlight paxillin as an intermediate signaling molecule that mediates actin stress fiber formation and VSMC migration through the Fyn/paxillin/Rho-kinase signaling pathway by directly binding to active Fyn. We also discuss the inhibition of VSMC migration by blocking the active Fyn-paxillin interaction and the potential of this interaction as a therapeutic target for cardiovascular diseases.

In contrast to the long-standing focus on the pathophysiology of skeletal muscles in the hunt for a cure for Duchenne muscular dystrophy (DMD), we opine that the malfunctioning of dystrophin produced by vascular smooth muscle is a major contributor to the pathology of the illness. We believe that a biological response modifier glucan (BRMG), which has been shown in clinical studies of DMD to boost the expression of vascular smooth muscle dystrophin and provide anti-fibrotic and anti-inflammatory effects, may play a key role in reducing the pathogenesis of DMD. According to the evaluation of biomarkers, this BRMG, which is safe and side-effect-free, reduces the pathogenesis of DMD. We describe the possible mechanisms of action by which this BRMG helps in alleviating the symptoms of DMD by targeting smooth muscle dystrophin, in addition to its advantages over other therapeutic modalities, as well as how it can serve as a valuable adjunct to existing therapies. We suggest that using BRMG adjuncts that target smooth muscle dystrophin would be a potential therapeutic approach that prolongs the lifespan and extends the duration of ambulation from the onset of DMD. Further studies are needed to validate this hypothesis.