The dynamic of senescent cells accumulation can explain the age-specific incidence of autoimmune diseases

Endothelial Senescence and Chronic Fatigue Syndrome, a COVID-19 Based Hypothesis

Myalgic encephalomyelitis/chronic fatigue syndrome is a serious illness of unknown etiology, characterized by debilitating exhaustion, memory impairment, pain and sleep abnormalities. Viral infections are believed to initiate the pathogenesis of this syndrome although the definite proof remains elusive. With the unfolding of COVID-19 pandemic, the interest in this condition has resurfaced as excessive tiredness, a major complaint of patients infected with the SARS-CoV-2 virus, often lingers for a long time, resulting in disability, and poor life quality. In a previous article, we hypothesized that COVID-19-upregulated angiotensin II triggered premature endothelial cell senescence, disrupting the intestinal and blood brain barriers. Here, we hypothesize further that post-viral sequelae, including myalgic encephalomyelitis/chronic fatigue syndrome, are promoted by the gut microbes or toxin translocation from the gastrointestinal tract into other tissues, including the brain. This model is supported by the SARS-CoV-2 interaction with host proteins and bacterial lipopolysaccharide. Conversely, targeting microbial translocation and cellular senescence may ameliorate the symptoms of this disabling illness.

Immune System Dysfunction in the Elderly

Human aging is characterized by both physical and physiological frailty that profoundly affects the immune system. In this context aging is associated with declines in adaptive and innate immunity established as immunosenescence. Immunosenescence is a new concept that reflects the age-associated restructuring changes of innate and adaptive immune functions. Thus elderly individuals usually present chronic low-level inflammation, higher infection rates and chronic diseases. A study of alterations in the immune system during aging could provide a potentially useful biomarker for the evaluation of immune senescence treatment. The immune system is the result of the interplay between innate and adaptive immunity, yet the impact of aging on this function is unclear. In this article the function of the immune system during aging is explored.

Role of miR-204 in the regulation of apoptosis, endoplasmic reticulum stress response, and inflammation in human trabecular meshwork cells

PURPOSE

To investigate the biological functions of miR-204 in human trabecular meshwork (HTM) cells.

METHODS

Changes in gene expression induced by miR-204 in HTM cells were evaluated by gene array analysis using arrays and confirmed by quantitative-PCR (Q-PCR). Direct targeting of miR-204 to 12 potential novel targets was confirmed using a luciferase system, and five of them were verified by Western blot analysis. Effects of miR-204 on apoptosis, cell viability, and accumulation of carbonylated proteins were evaluated in HTM cells treated with H(2)O(2). Induction of endoplasmic reticulum (ER) stress markers by tunicamycin was analyzed by Q-PCR, and expression of IL-8 and IL-11 was analyzed by ELISA.

RESULTS

MiR-204 decreased the expression of multiple genes in HTM cells. Twelve genes (AP1S2, Bcl2l2, BIRC2, EDEM1, EZR, FZD1, M6PR, RAB22A, RAB40B, SERP1, TCF12, and TCF4) were validated as direct targets of miR-204. Downregulation of expressions at protein levels of Bcl2l2, BIRC2, EZR, M6PR, and SERP1 were confirmed by Western blot analysis. HTM cells transfected with miR-204 showed increased levels of apoptosis, decreased viability, increased accumulation of oxidized proteins after H(2)O(2) treatment, decreased induction of ER stress response markers, and reduced expression of inflammatory mediators IL-8 and IL-11.

CONCLUSIONS

MiR-204 potentially plays an important role in the regulation of multiple functions in HTM cells including apoptosis, accumulation of damaged proteins, ER stress response, and expression of inflammatory mediators.

Modulation of inflammatory markers by miR-146a during replicative senescence in trabecular meshwork cells

PURPOSE

To investigate the alterations in microRNA (miRNA) expression during replicative senescence (RS) in human trabecular meshwork (HTM) cells.

METHODS

Two HTM cell lines were serially passaged until they reached RS. Changes in expression of 30 miRNAs were assessed by real-time quantitative (q)-PCR. The effects of miR-146a on gene expression were analyzed with gene arrays and the results confirmed by real-time q-PCR. Protein levels of IRAK1 and PAI-1 were analyzed by Western blot and those of IL6 and IL8 by ELISA. Senescence-associated markers were monitored by flow cytometry and cell proliferation by BrdU incorporation.

RESULTS

RS of HTM cells was associated with significant changes in expression of 18 miRNAs, including the upregulation of miR-146a. miR-146a downregulated multiple genes associated with inflammation, including IRAK1, IL6, IL8, and PAI-1, inhibited senescence-associated beta-galactosidase (SA-beta-gal) activity and production of intracellular reactive species (iROS), and increased cell proliferation. Overexpression of either IRAK1 or PAI-1 inhibited the effects of miR-146a on cell proliferation and iROS production in senescent cells.

CONCLUSIONS

RS in HTM cells was associated with changes in miRNA expression that could influence the senescent phenotype. Upregulation of the anti-inflammatory miR-146a may serve to restrain excessive production of inflammatory mediators in senescent cells and limit their deleterious effects on the surrounding tissue. Among the different proteins repressed by miR-146a, the inhibition of PAI-1 may act to minimize the effects of senescence on the generation of iROS and growth arrest and prevent alterations of the extracellular proteolytic activity of the TM.