Wnt-induced, TRP53-mediated Cell Cycle Arrest of Precursors Underlies Interstitial Cell of Cajal Depletion During Aging

Ca2+ dynamics in interstitial cells: foundational mechanisms for the motor patterns in the gastrointestinal tract

The gastrointestinal (GI) tract displays multiple motor patterns that move nutrients and wastes through the body. Smooth muscle cells (SMCs) provide the forces necessary for GI motility, but interstitial cells, electrically coupled to SMCs, tune SMC excitability, transduce inputs from enteric motor neurons, and generate pacemaker activity that underlies major motor patterns, such as peristalsis and segmentation. The interstitial cells regulating SMCs are interstitial cells of Cajal (ICC) and PDGF receptor (PDGFR)α+ cells. Together these cells form the SIP syncytium. ICC and PDGFRα+ cells express signature Ca2+-dependent conductances: ICC express Ca2+-activated Cl- channels, encoded by Ano1, that generate inward current, and PDGFRα+ cells express Ca2+-activated K+ channels, encoded by Kcnn3, that generate outward current. The open probabilities of interstitial cell conductances are controlled by Ca2+ release from the endoplasmic reticulum. The resulting Ca2+ transients occur spontaneously in a stochastic manner. Ca2+ transients in ICC induce spontaneous transient inward currents and spontaneous transient depolarizations (STDs). Neurotransmission increases or decreases Ca2+ transients, and the resulting depolarizing or hyperpolarizing responses conduct to other cells in the SIP syncytium. In pacemaker ICC, STDs activate voltage-dependent Ca2+ influx, which initiates a cluster of Ca2+ transients and sustains activation of ANO1 channels and depolarization during slow waves. Regulation of GI motility has traditionally been described as neurogenic and myogenic. Recent advances in understanding Ca2+ handling mechanisms in interstitial cells and how these mechanisms influence motor patterns of the GI tract suggest that the term "myogenic" should be replaced by the term "SIPgenic," as this review discusses.

The Crucial Role of the Interstitial Cells of Cajal in Neurointestinal Diseases

Neurointestinal diseases result from dysregulated interactions between the nervous system and the gastrointestinal (GI) tract, leading to conditions such as Hirschsprung's disease and irritable bowel syndrome. These disorders affect many people, significantly diminishing their quality of life and overall health. Central to GI motility are the interstitial cells of Cajal (ICC), which play a key role in muscle contractions and neuromuscular transmission. This review highlights the role of ICC in neurointestinal diseases, revealing their association with various GI ailments. Understanding the functions of the ICC could lead to innovative perspectives on the modulation of GI motility and introduce new therapeutic paradigms. These insights have the potential to enhance efforts to combat neurointestinal diseases and may lead to interventions that could alleviate or even reverse these conditions.

Insulin-Like Growth Factor1 Preserves Gastric Pacemaker Cells and Motor Function in Aging via ERK1/2 Activation

BACKGROUND & AIMS

Impaired gastric motor function in the elderly causes reduced food intake leading to frailty and sarcopenia. We previously found that aging-related impaired gastric compliance was mainly owing to depletion of interstitial cells of Cajal (ICC), pacemaker cells, and neuromodulator cells. These changes were associated with reduced food intake. Transformation-related protein 53-induced suppression of extracellular signal-regulated protein kinase (ERK)1/2 in ICC stem cell (ICC-SC) cell-cycle arrest is a key process for ICC depletion and gastric dysfunction during aging. Here, we investigated whether insulin-like growth factor 1 (IGF1), which can activate ERK in gastric smooth muscles and invariably is reduced with age, could mitigate ICC-SC/ICC loss and gastric dysfunction in klotho mice, a model of accelerated aging.

METHODS

Klotho mice were treated with the stable IGF1 analog LONG R3 recombinant human (rh) IGF1 (150 μg/kg intraperitoneally twice daily for 3 weeks). Gastric ICC/ICC-SC and signaling pathways were studied by flow cytometry, Western blot, and immunohistochemistry. Gastric compliance was assessed in ex vivo systems. Transformation-related protein 53 was induced with nutlin 3a and ERK1/2 signaling was activated by rhIGF-1 in the ICC-SC line.

RESULTS

LONG R3 rhIGF1 treatment prevented reduced ERK1/2 phosphorylation and gastric ICC/ICC-SC decrease. LONG R3 rhIGF1 also mitigated the reduced food intake and impaired body weight gain. Improved gastric function by LONG R3 rhIGF1 was verified by in vivo systems. In ICC-SC cultures, rhIGF1 mitigated nutlin 3a-induced reduced ERK1/2 phosphorylation and cell growth arrest.

CONCLUSIONS

IGF1 can mitigate age-related ICC/ICC-SC loss by activating ERK1/2 signaling, leading to improved gastric compliance and increased food intake in klotho mice.

Cellular Senescence, Inflammation, and Cancer in the Gastrointestinal Tract

Due to modern medical advancements, greater proportions of the population will continue to age with longer life spans. Increased life span, however, does not always correlate with improved health span, and may result in an increase in aging-related diseases and disorders. These diseases are often attributed to cellular senescence, in which cells become disengaged from the cell cycle and inert to cell death. These cells are characterized by a proinflammatory secretome. The proinflammatory senescence-associated secretory phenotype, although part of a natural function intended to prevent further DNA damage, creates a microenvironment suited to tumor progression. This microenvironment is most evident in the gastrointestinal tract (GI), where a combination of bacterial infections, senescent cells, and inflammatory proteins can lead to oncogenesis. Thus, it is important to find potential senescence biomarkers as targets of novel therapies for GI diseases and disorders including cancers. However, finding therapeutic targets in the GI microenvironment to reduce the risk of GI tumor onset may also be of value. This review summarizes the effects of cellular senescence on GI aging, inflammation, and cancers, and aims to improve our understanding of these processes with a goal of enhancing future therapy.

Wnt Signaling and Aging of the Gastrointestinal Tract

Aging is considered a risk factor for various diseases including cancers. In this aging society, there is an urgent need to clarify the molecular mechanisms involved in aging. Wnt signaling has been shown to play a crucial role in the maintenance and differentiation of tissue stem cells, and intensive studies have elucidated its pivotal role in the aging of neural and muscle stem cells. However, until recently, such studies on the gastrointestinal tract have been limited. In this review, we discuss recent advances in the study of the role of Wnt signaling in the aging of the gastrointestinal tract and aging-related carcinogenesis.

Zuogui Wan slowed senescence of bone marrow mesenchymal stem cells by suppressing Wnt/β-catenin signaling

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine (TCM), Zuogui Wan (ZGW) is a classical prescription for senile disorders and delay aging. Modern studies show that ZGW promotes central nerve cell regeneration, prevents and cures osteoporosis, enhances the body's antioxidant capacity, regulates the body's immune function, and promotes mesenchymal stem cells (MSCs) proliferation.

AIM OF THE STUDY

It has been shown that MSCs aging is closely associated with organism's aging and age-related disorders. The study aimed to define the effects of ZGW on the aging bone marrow mesenchymal stem cells (BMSCs) and to identify the mechanisms of ZGW delaying BMSCs senescence.

MATERIALS AND METHODS

Network pharmacology analysis combined with GEO data mining, molecular docking and experimental validation were used to evaluate the mechanisms by which ZGW delays MSCs senescence (MSCS). LC-MS was used for quality control analysis of ZGW.

RESULTS

PPI network analysis revealed that EGF, TNF, JUN, MMPs, IL-6, MAPK8, and MYC are components of the core PPI network. GO and KEGG analyses revealed that oxidative stress, regulation of response to DNA damage stimuli, and Wnt signaling were significantly enriched. GEO database validation also indicated that Wnt signaling closely correlated with MSCs aging. Molecular docking analysis of the top-13 active components in the "ZGW-Targets-MSCS" network indicated that most components have strong affinity for key proteins in Wnt signaling, suggesting that modulation of Wnt signaling is an important mechanism of ZGW activity against MSCS. Further experimental validation found that ZGW indeed regulates Wnt signaling and suppresses the expression of age-related factors to enhance cell proliferation, ameliorate DNA damage, and reduce senescence-related secretory phenotype (SASP) secretion, thereby maintaining multidirectional differentiation of rat BMSCs. Similar results were obtained using the Wnt inhibitor, XAV-939.

CONCLUSIONS

Together, our data show that ZGW slows BMSCs aging by suppressing Wnt signaling.

Aging of enteric neuromuscular systems in gastrointestinal tract

BACKGROUND

Aging is a complex biological process and associated with a progressive decline in functions of most organs including the gastrointestinal (GI) tract. Age-related GI motor disorders/dysfunctions include esophageal reflux, dysphagia, constipation, fecal incontinence, reduced compliance, and accommodation. Although the incidence and severity of these diseases and conditions increase with age, they are often underestimated due in part to nonspecific and variable symptoms and lack of sufficient medical attention. They negatively affect quality of life and predispose the elderly to other diseases, sarcopenia, and frailty. The mechanisms underlying aging-associated GI dysfunctions remain unclear, and there is limited data examining the effect of aging on GI motor functions. Many studies on aging-associated changes to cells within the tunica muscularis including enteric neurons, smooth muscles, and interstitial cells have proposed that cell loss and/or molecular changes may be involved in the pathogenesis of age-related GI motor disorders/dysfunctions. There is also evidence that the aging contributes to phenotypic changes in innate immune cells, which are physically and functionally linked to other cells in the tunica muscularis and can alter GI (patho) physiology. However, various patterns of changes have been reported, some of which are contradictory, indicating a need for additional work in this area.

PURPOSE

Although GI infection due to intestinal bacterial overgrowth, bleeding, and cancers are also important and common problems in the elderly patients, this mini-review focuses on data obtained from enteric neuromuscular aging research with the goal of better understanding the cellular and molecular mechanisms of enteric neuromuscular aging to enhance future therapy.

A narrative review of imatinib-resistant gastrointestinal stromal tumors

Objective:

Review the studies that investigate the mechanisms underlying imatinib-resistant gastrointestinal stromal tumors (GIST).

Background:

GIST are the most common mesenchymal tumors of the gastrointestinal (GI) tract and the most common sarcoma in humans. GIST are thought to be arise from interstitial cells of Cajal (ICC), pacemaker and neuromodulator cells in the GI tract, as well as “fibroblast”-like cells, which are another type of interstitial cells of the gut wall and also known as telocyte or platelet-derived growth factor-alpha (PDGFRA)-positive cells. The majority of GIST harbor gain-of-function mutations in either KIT or PDGFRA, and these gain-of-function mutations are mutually exclusive and most often heterozygous. GIST are responsive to the KIT/PDGFRA tyrosine kinase inhibitor (TKI), imatinib, the standard first-line drug for advanced and metastatic GIST. However, imatinib alone does not eradicate GIST despite an initial clinical benefit, and more than 90% of GIST harbor imatinib-resistance. Although second and third-generation TKIs have been developed and are currently in clinical use, they are not curative for refractory and metastatic GIST due to the emergence of clones with drug-resistant mutations. Eradication of drug-resistant GIST will cure patients with refractory GIST. Several mechanisms may contribute to refractory GIST. These mechanisms are secondary mutations in KIT and/or PDGFRA, alternative activation of tyrosine kinases, stem cells for GIST and cellular quiescence, a reversible nonproliferating state in which cells retain the ability to reenter cell proliferation.

Methods:

We review our current optimal treatment approach for managing patients with advanced and refractory GIST.

Conclusions:

This review explores the novel and potential therapeutic approaches to combat drug-resistant GIST.