Deciphering RNA m6A regulation in aging: Perspectives on current advances and future directions

N⁶-methyladenosine (m⁶A) is a dynamic and reversible RNA modification that has emerged as a crucial player in the life cycle of RNA, thus playing a pivotal role in various biological processes. In recent years, the potential involvement of RNA m⁶A modification in aging and age-related diseases has gained increasing attention, making it a promising target for understanding the molecular mechanisms underlying aging and developing new therapeutic strategies. This Perspective article will summarize the current advances in aging-related m⁶A regulation, highlighting the most significant findings and their implications for our understanding of cellular senescence and aging, and the potential for targeting RNA m⁶A regulation as a therapeutic strategy. We will also discuss the limitations and challenges in this field and provide insights into future research directions. By providing a comprehensive overview of the current state of the field, this Perspective article aims to facilitate further advances in our understanding of the molecular mechanisms underlying aging and to identify new therapeutic targets for aging-related diseases.     

Bifidobacterium longum supplementation improves age-related delays in fracture repair

Age-related delays in bone repair remains an important clinical issue that can prolong pain and suffering. It is now well established that inflammation increases with aging and that this exacerbated inflammatory response can influence skeletal regeneration. Recently, simple dietary supplementation with beneficial probiotic bacteria has been shown to influence fracture repair in young mice. However, the contribution of the gut microbiota to age-related impairments in fracture healing remains unknown. Here, we sought to determine whether supplementation with a single beneficial probiotic species, Bifidobacterium longum (B. longum), would promote fracture repair in aged (18-month-old) female mice. We found that B. longum supplementation accelerated bony callus formation which improved mechanical properties of the fractured limb. We attribute these pro-regenerative effects of B. longum to preservation of intestinal barrier, dampened systemic inflammation, and maintenance of the microbiota community structure. Moreover, B. longum attenuated many of the fracture-induced systemic pathologies. Our study provides evidence that targeting the gut microbiota using simple dietary approaches can improve fracture healing outcomes and minimize systemic pathologies in the context of aging.     

Role of pulmonary epithelial arginase-II in activation of fibroblasts and lung inflammaging

Elevated arginases including type-I (Arg-I) and type-II isoenzyme (Arg-II) are reported to play a role in aging, age-associated organ inflammaging, and fibrosis. A role of arginase in pulmonary aging and underlying mechanisms are not explored. Our present study shows increased Arg-II levels in aging lung of female mice, which is detected in bronchial ciliated epithelium, club cells, alveolar type 2 (AT2) pneumocytes, and fibroblasts (but not vascular endothelial and smooth muscle cells). Similar cellular localization of Arg-II is also observed in human lung biopsies. The age-associated increase in lung fibrosis and inflammatory cytokines, including IL-1β and TGF-β1 that are highly expressed in bronchial epithelium, AT2 cells, and fibroblasts, are ameliorated in arg-ii deficient (arg-ii^−/−) mice. The effects of arg-ii^−/− on lung inflammaging are weaker in male as compared to female animals. Conditioned medium (CM) from human Arg-II-positive bronchial and alveolar epithelial cells, but not that from arg-ii^−/− cells, activates fibroblasts to produce various cytokines including TGF-β1 and collagen, which is abolished by IL-1β receptor antagonist or TGF-β type I receptor blocker. Conversely, TGF-β1 or IL-1β also increases Arg-II expression. In the mouse models, we confirmed the age-associated increase in IL-1β and TGF-β1 in epithelial cells and activation of fibroblasts, which is inhibited in arg-ii^−/− mice. Taken together, our study demonstrates a critical role of epithelial Arg-II in activation of pulmonary fibroblasts via paracrine release of IL-1β and TGF-β1, contributing to pulmonary inflammaging and fibrosis. The results provide a novel mechanistic insight in the role of Arg-II in pulmonary aging.     

Exercise enhancement by RGS14 disruption is mediated by brown adipose tissue

Enhanced exercise capacity is not only a feature of healthful aging, but also a therapy for aging patients and patients with cardiovascular disease. Disruption of the Regulator of G Protein Signaling 14 (RGS14) in mice extends healthful lifespan, mediated by increased brown adipose tissue (BAT). Accordingly, we determined whether RGS14 knockout (KO) mice exhibit enhanced exercise capacity and the role of BAT in mediating exercise capacity. Exercise was performed on a treadmill and exercise capacity was assessed by maximal running distance and work to exhaustion. Exercise capacity was measured in RGS14 KO mice and their wild types (WT), and also in WT mice with BAT transplantation from RGS14 KO mice or from other WT mice. RGS14 KO mice demonstrated 160 ± 9% increased maximal running distance and 154 ± 6% increased work to exhaustion, compared to WT mice. RGS14 KO BAT transplantation to WT mice, resulted in a reversal of phenotype, with the WT mice receiving the BAT transplant from RGS14 KO mice demonstrating 151 ± 5% increased maximal running distance and 158 ± 7% increased work to exhaustion, at three days after BAT transplantation, compared to RGS14 KO donors. BAT transplantation from WT to WT mice also resulted in increased exercise performance, but not at 3 days, but only at 8 weeks after transplantation. The BAT induced enhanced exercise capacity was mediated by (1) mitochondrial biogenesis and SIRT3; (2) antioxidant defense and the MEK/ERK pathway, and increased hindlimb perfusion. Thus, BAT mediates enhanced exercise capacity, a mechanism more powerful with RGS14 disruption.     

Age-mediated gut microbiota dysbiosis promotes the loss of dendritic cells tolerance

The old age-related loss of immune tolerance inflicts a person with a wide range of autoimmune and inflammatory diseases. Dendritic cells (DCs) are the sentinels of the immune system that maintain immune tolerance through cytokines and regulatory T-cells generation. Aging disturbs the microbial composition of the gut, causing immune system dysregulation. However, the vis-à-vis role of gut dysbiosis on DCs tolerance remains highly elusive. Consequently, we studied the influence of aging on gut dysbiosis and its impact on the loss of DC tolerance. We show that DCs generated from either the aged (DC^Old) or gut-dysbiotic young (DC^Dysbiotic) but not young (DC^Young) mice exhibited loss of tolerance, as evidenced by their failure to optimally induce the generation of Tregs and control the overactivation of CD4⁺ T cells. The mechanism deciphered for the loss of DC^Old and DC^Dysbiotic tolerance was chiefly through the overactivation of NF-κB, impaired frequency of Tregs, upregulation in the level of pro-inflammatory molecules (IL-6, IL-1β, TNF-α, IL-12, IFN-γ), and decline in the anti-inflammatory moieties (IL-10, TGF-β, IL-4, IDO, arginase, NO, IRF-4, IRF-8, PDL1, BTLA4, ALDH2). Importantly, a significant decline in the frequency of the Lactobacillus genus was noticed in the gut. Replenishing the gut of old mice with the Lactobacillus plantarum reinvigorated the tolerogenic function of DCs through the rewiring of inflammatory and metabolic pathways. Thus, for the first time, we demonstrate the impact of age-related gut dysbiosis on the loss of DC tolerance. This finding may open avenues for therapeutic intervention for treating age-associated disorders with the Lactobacillus plantarum.     

Selenium in combination with a tomato lipid extract as a therapy for benign prostatic hyperplasia and its alterations in rats with induced BPH

Benign prostatic hyperplasia (BPH) is the most common adenoma in old men. Tomatoes are a rich source of bioactive compounds that, as well as selenium (Se), possess antioxidant and antiproliferative activity. The aim was to evaluate the therapeutic effect of Se in combination with a tomato extract in aged rats with BPH. Aged male Wistar rats were divided in the following groups (n = 10 rats/group): Control (C), BPH, BPH + Finasteride (BPH + F), BPH + Tomato Lipidic Extract (BPH + E), BPH + Selenium (BPH + S) and BPH plus E plus S (BPH + E + S). After 4 weeks of treatment, prostate weight, diuresis, antioxidants enzymes, prooxidants and inflammatory markers, growth factors and androgens were determined. BPH + E + S reduced prostate weight by 59.29% and inhibited growth by 99.35% compared to BPH + F which only decreased weight and inhibited growth by 15.31% and 57.54%, respectively. Prooxidant markers were higher with BPH + F (49.4% higher vs. BPH), but BPH + E + S decreased these markers (94.27% vs. BPH) and increased antioxidant activity. Finally, diuresis was higher with the BPH + E + S combination and markers of inflammation and growth factors were significantly lower with respect to BPH + F. Our findings provide a beneficial and protective therapeutic option of E + S directed against androgens, oxidative stress and inflammation that regulates cell proliferation in the prostate gland.     

In vitro aging of calmodulin generates isoaspartate at multiple Asn-Gly and Asp-Gly sites in calcium-binding domains II, III, and IV.

We have determined the major sites responsible for isoaspartate formation during in vitro aging of bovine brain calmodulin under mild conditions. Protein L-isoaspartyl methyltransferase (EC 2.1.1.77) was used to quantify isoaspartate by the transfer of methyl-3H from S-adenosyl-L-[methyl-3H]methionine to the isoaspartyl (alpha-carboxyl) side chain. More than 1.2 mol of methyl-acceptor sites per mol of calmodulin accumulated during a 2-week incubation without calcium at pH 7.4, 37 degrees C. Analysis of proteolytic peptides of aged calmodulin revealed that > 95% of the methylation capacity is restricted to residues in the four calcium-binding domains, which are predicted to be highly flexible in the absence of calcium. We estimate that domains III, IV, and II accumulated 0.72, 0.60, and 0.13 mol of isoaspartate per mol of calmodulin, respectively. The Asn-97-Gly-98 sequence (domain III) is the greatest contributor to isoaspartate formation. Other major sites of isoaspartate formation are Asp-131-Gly-132 and Asp-133-Gly-134 in domain IV, and Asn-60-Gly-61 in domain II. Significant isoaspartate formation was also localized to Asp-20, Asp-22, and/or Asp-24 in domain I, to Asp-56 and/or Asp-58 in domain II, and to Asp-93 and/or Asp-95 in domain III. All of these residues are calcium ligands in the highly conserved EF-hand calcium-binding motif. Thus, other EF-hand proteins may also be subject to isoaspartate formation at these ligands. The results support the idea that isoaspartate formation in structured proteins is strongly influenced by both the C-flanking residue and by local flexibility.     

Aluminum Toxicity: A Case Study on Tobacco (<i>Nicotiana tabacum</i> L.)

Aluminum is an abundant metal in the earth’s crust that turns out to be toxic in acidic environments. Many plants are affected by the presence of aluminum at the whole plant level, at the organ level, and at the cellular level. Tobacco as a cash crop (Nicotiana tabacum L.) is a widely cultivated plant worldwide and is also a good model organism for research. Although there are many articles on Al-phytotoxicity in the literature, reviews on a single species that are economically and scientifically important are limited. In this article, we not only provide the biology associated with tobacco Al-toxicity, but also some essential information regarding the effects of this metal on other plant species (even animals). This review provides information on aluminum localization and uptake process by different staining techniques, as well as the effects of its toxicity at different compartment levels and the physiological consequences derived from them. In addition, molecular studies in recent years have reported specific responses to Al toxicity, such as overexpression of various protective proteins. Besides, this review discusses data on various organelle-based responses, cell death, and other mechanisms, data on tobacco plants and other kingdoms relevant to these studies.