Increased susceptibility of aging gastric mucosa to injury:The mechanisms and clinical implications

This review updates the current views on aging gastric mucosa and the mechanisms of its increased susceptibility to injury.Experimental and clinical studies indicate that gastric mucosa of aging individuals-"aging gastropathy"-has prominent structural and functional abnormalities vs young gastric mucosa.Some of these abnormalities include a partial atrophy of gastric glands,impaired mucosal defense(reduced bicarbonate and prostaglandin generation,decreased sensory innervation),increased susceptibility to injury by a variety of damaging agents such as ethanol,aspirin and other non-steroidal anti-inflammatory drugs(NSAIDs),impaired healing of injury and reduced therapeutic efficacy of ulcer-healing drugs.Detailed analysis of the above changes indicates that the following events occur in aging gastric mucosa:reduced mucosal blood flow and impaired oxygen delivery cause hypoxia,which leads to activation of the early growth response-1(egr-1)transcription factor.Activation of egr-1,in turn,upregulates the dual specificity phosphatase,phosphatase and tensin homologue deleted on chromosome ten(PTEN)resulting in activation of pro-apoptotic caspase-3 and caspase-9 and reduced expression of the anti-apoptosis protein,survivin.The imbalance between pro-and anti-apoptosis mediators results in increased apoptosis and increased susceptibility to injury.This paradigm has human relevance since increased expression of PTEN and reduced expression of survivin were demonstrated in gastric mucosa of aging individuals.Other potential mechanisms operating in aging gastric mucosa include reduced telomerase activity,increase in replicative cellular senescence,and reduced expression of vascular endothelial growth factor and importin-α-a nuclear transport protein essential for transport of transcription factors to nucleus.Aging gastropathy is an important and clinically relevant issue because of:(1)an aging world population due to prolonged life span;(2)older patients have much greater risk of gastroduodenal ulcers and gastrointestinal complications(e.g.,NSAIDs-induced gastric injury)than younger patients;and(3)increased susceptibility of aging gastric mucosa to injury can be potentially reduced or reversed pharmacologically.

Increased susceptibility of aging gastric mucosa to injury and delayed healing:Clinical implications

In this editorial we comment on the article by Fukushi K et al published in the recent issue of the World Journal of Gastroenterology 2018; 24(34): 3908-3918. We focus specifically on the mechanisms of the anti-thrombotic action of aspirin, gastric mucosal injury and aging-related increased susceptibility of gastric mucosa to injury. Aspirin is widely used not only for the management of acute and chronic pain and arthritis, but also importantly for the primary and secondary prevention of cardiovascular events such as myocardial infarcts and strokes. Clinical trials have consistently shown that antiplatelet therapy with long term, low dose aspirin(LDA)-75 to 325 mg daily, dramatically reduces the risk of non-fatal myocardial infarcts, stroke and mortality in patients with established arterial diseases. However, such treatment considerably increases the risk of gastrointestinal(GI) ulcerations and serious bleeding by > 2-4 fold, especially in aging individuals. This risk is further increased in patients using LDA together with other antiplatelet agents, other nonsteroidal anti-inflammatory agents(NSAIDs) and/or alcohol, or in patients with Helicobacter pylori(H. pylori) infection. Previous studies by our group and others have demonstrated prominent structural and functional abnormalities in gastric mucosa of aging individuals(which we refer to as aging gastric mucosa or "aging gastropathy") compared to the gastric mucosa of younger individuals. Aging gastric mucosa has impaired mucosal defense, increased susceptibility to injury by a variety of noxious agents such as aspirin, other NSAIDs and ethanol, and delayed and impaired healing of injury. The mechanism underlying these abnormalities of aging gastric mucosa include reduced mucosal blood flowcausing hypoxia, upregulation of PTEN, activation of proapoptotic caspase-3 and caspase-9, and reduced survivin(anti-apoptosis protein), importin-α(nuclear transport protein), vascular endothelial growth factor, and nerve growth factor. The decision regarding initiation of a long-term LDA therapy should be made after a careful consideration of both cardiovascular and GI risk factors. The latter include a previous history of GI bleeding and/or ulcers, age ≥ 70, male gender, concurrent use of other NSAIDs, alcohol consumption and H. pylori infection. Furthermore, the incidence of GI ulcers and bleeding can be reduced in patients on long term LDA treatment by several measures. Clinicians treating such patients should test for and eradicate H. pylori, instruct patients to avoid alcohol and non-aspirin NSAIDs, including cyclooxygenase-2-selective NSAIDs, and prescribe proton pump inhibitors in patients on LDA therapy. In the future, clinicians may be able to prescribe one of several potential new drugs, which include aspirin associated with phosphatidylcholine(PL2200), which retains all property of aspirin but reduces by approximately 50% LDA-induced GI ulcerations.

Endothelial cells and blood vessels are major targets for COVID-19-induced tissue injury and spreading to various organs

The coronavirus disease 2019(COVID-19)infected so far over 250 million people and caused the death of over 5 million worldwide.Aging,diabetes,and cardiovascular diseases,conditions with preexisting impaired endothelial functions predispose to COVID-19.While respiratory epithelium is the main route of virus entry,the endothelial cells(ECs)lining pulmonary blood vessels are also an integral part of lung injury in COVID-19 patients.COVID-19 not only affects the lungs and respiratory system but also gastrointestinal(GI)tract,liver,pancreas,kidneys,heart,brain,and skin.Blood vessels are likely conduits for the virus dissemination to these distant organs.Importantly,ECs are also critical for vascular regeneration during injury/lesions healing and restoration of vascular network.The World Journal of Gastroenterology has published in last two years over 67 outstanding papers on COVID-19 infection with a focus on the GI tract,liver,pancreas,etc.,however,the role of the endothelial and vascular components as major targets for COVID-19-induced tissue injury,spreading to various organs,and injury healing have not been sufficiently emphasized.In the present article,we focus on these subjects and on current treatments including the most recent oral drugs molnupiravir and paxlovid that show a dramatic,significant efficacy in controlling severe COVID-19 infection.