Loss of ischemic tolerance with age: can we protect an old kidney

The most abundant and vulnerable cohort of patients with acute kidney injury (AKI) is represented by the older people. It is well-known, the kidney tissue undergoes some changes with age, both at the morphological and molecular level. Therefore, when treating AKI in older patients, it is necessary to take into account the morphofunctional features of aging kidney tissue and metabolic alterations. We have shown that the kidney of old rats does not perceive signals from the most well-known protective approaches such as ischemic preconditioning (IPC) and caloric restriction (CR). Although the old kidney did not develop more severe AKI after ischemia, we found no pronounced effect on attempts to increase its resistance by IPC and CR. Analysis of the mechanisms underlying this loss of tolerance has shown that the most affected pathways are the mechanism of mitochondrial quality control, the effectiveness of autophagy, and the proliferative potential of kidney cells. However, several protective pathways activated in the young kidney were also active in the old one in response to the CR. In particular, an increase in SIRT1 deacetylase, antiapoptotic Bcl-xL, and a decrease in oxidative stress were observed. Our results show that some defense systems demonstrating their effectiveness in young organisms lose their beneficial effect in old organisms, while others still can be activated by protective approaches. Thus, it is necessary to carefully analyze the possibilities of increasing ischemic tolerance for old organisms. This work was supported by the Russian science foundation (grant #21-75-30009).

Aristolochic Acid Induces Renal Fibrosis and Senescence in Mice

The kidney is one of the most susceptible organs to age-related impairments. Generally, renal aging is accompanied by renal fibrosis, which is the final common pathway of chronic kidney diseases. Aristolochic acid (AA), a nephrotoxic agent, causes AA nephropathy (AAN), which is characterized by progressive renal fibrosis and functional decline. Although renal fibrosis is associated with renal aging, whether AA induces renal aging remains unclear. The aim of the present study is to investigate the potential use of AAN as a model of renal aging. Here, we examined senescence-related factors in AAN models by chronically administering AA to C57BL/6 mice. Compared with controls, the AA group demonstrated aging kidney phenotypes, such as renal atrophy, renal functional decline, and tubulointerstitial fibrosis. Additionally, AA promoted cellular senescence specifically in the kidneys, and increased renal p16 mRNA expression and senescence-associated β-galactosidase activity. Furthermore, AA-treated mice exhibited proximal tubular mitochondrial abnormalities, as well as reactive oxygen species accumulation. Klotho, an antiaging gene, was also significantly decreased in the kidneys of AA-treated mice. Collectively, the results of the present study indicate that AA alters senescence-related factors, and that renal fibrosis is closely related to renal aging.

The Aging Kidney—As Influenced by Heavy Metal Exposure and Selenium Supplementation

The aging process in the kidneys has been well studied. It is known that the glomerular filtration rate (GFR) declines with age in subjects older than 50–60 years. However, there is still insufficient knowledge regarding the response of the aged kidney to environmental toxicants such as mercury, cadmium, and lead. Here, we present a review on the functional decline and proposed mechanisms in the aging kidney as influenced by metal pollutants. Due to the prevalence of these toxicants in the environment, human exposure is nearly unavoidable. Further, it is well known that acute and chronic exposures to toxic metals may be detrimental to kidneys of normal adults, thus it may be hypothesized that exposure of individuals with reduced GFR will result in additional reductions in renal function. Individuals with compromised renal function, either from aging or from a combination of aging and disease, may be particularly susceptible to environmental toxicants. The available data appear to show an association between exposure to mercury, cadmium and/or lead and an increase in incidence and severity of renal disease in elderly individuals. Furthermore, some physiological thiols, as well as adequate selenium status, appear to exert a protective action. Further studies providing improved insight into the mechanisms by which nephrotoxic metals are handled by aging kidneys, as well as possibilities of therapeutic protection, are of utmost importance.

REST and Stress Resistance in the Aging Kidney

Background: Chronic kidney disease is associated with the loss of functional nephrons, leading to increased mechanical and metabolic stress in the remaining cells, particularly for cells constituting the filtration barrier, such as podocytes. The failure of podocytes to mount an adequate stress response can lead to further nephron loss and disease progression. However, the mechanisms that regulate this degenerative process in the kidney are unknown. Methods: We combined in vitro, in vivo, and organ-on-chip approaches to identify the RE1-silencing transcription factor (REST), a repressor of neuronal genes during embryonic development, as a central regulator of podocyte adaptation to injury and aging. Results: Mice with a specific deletion of REST in podocytes exhibit albuminuria, podocyte apoptosis, and glomerulosclerosis during aging, and exhibit increased vulnerability to renal injury. This phenotype is mediated, in part, by effects of REST on the podocyte cytoskeleton that promote resistance to mechanical stressors and augment podocyte survival. Finally, REST expression is upregulated in human podocytes during aging, consistent with a conserved mechanism of stress resistance. Conclusions: These results suggest that REST protects the kidney from injury and degeneration during aging, with potentially important therapeutic implications.

Role of tubular epithelial arginase-II in renal inflammaging

The aging kidney undergoes complex changes and is vulnerable to injury and development of chronic kidney disease (CKD) with preponderance affecting more women than men. Evidence has been presented that the type-II L-arginine:ureohydrolase, arginase-II (Arg-II) plays a role in the acceleration of aging. Arg-II is highly expressed in the kidney. However, the role of Arg-II in renal aging is not known. This study is to investigate whether Arg-II is involved in the kidney aging process dependently on sex. Arg-II level in the kidney of wild type (WT) mice is significantly elevated with aging, which is accompanied by an increase in expression of the inflammatory cytokines/chemokines, tissue macrophages, factors involved in fibrosis, and tubulointestitial fibrosis in both males and females. This renal aging phenotype is significantly suppressed in arg-II−/− mice, mainly in the females in which Arg-II level is higher than in the males. Importantly, numerous factors such as IL-1β, MCP1, VCAM-1, and TGFβ1 are mainly localized in the proximal tubular S3 segment cells expressing Arg-II in the aging kidney. In human proximal tubular cells (HK-2), TNF-α enhances adhesion molecule expression dependently on Arg-II upregulation. Overexpression of Arg-II in the cells enhances TGFβ1 levels which is prevented by mitochondrial ROS inhibition. In summary, our study reveals that renal proximal tubular Arg-II plays an important role in the kidney aging process in females. Arg-II could be a promising therapeutic target for the treatment and prevention of aging-associated kidney diseases.

Lipid Peroxidation: Aging Kidney

Kidney is one of the tissues affected by age that involves cellular and structural changes inside the kidney and notably implicates with comorbidity, related to cardiovascular disease aging. Aging kidney causes the elderly susceptible to clinical deterioration from ordinary stimulation that younger individual can compensate, including acute renal injury, volume depletion or overload, sodium and potassium level disorders, and toxic reaction against kidney excreted drugs. As one of the organs with the fastest aging rate, kidney shows several age-related decline in both structural and functional with 30% of the glomerulus are damaged and represent diffuse glomerular sclerosis by age 75 and explain why the prevalence of chronic kidney disease (CKD) and end-stage renal disease are very common in the elderly. The cross-sectional population-based study by The National Health and Nutrition Examination Survey supports the theory of age-related decline in kidney function, although some other subjects did not have an absolute decline in kidney function. The underlying molecular mechanisms could be the target of future therapeutic strategies. Aging is a natural biological process characterized by a gradual decline in cellular function as well as progressive structural change of organ systems. In aging kidney, there are interactions of genetic factors, environmental changes, and cellular dysfunction that lead to the typical structural and functional changes. One of the most popular theory of aging is the theory of free radicals or oxidative stress based on the fact that cells are under chronic oxidative stress due to an imbalance between pro oxidants and antioxidants. Reactive oxygen species are oxygen-derived oxidizing compounds that are highly reactive, consisting of free radicals and non-radicals. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) refer to both reactive radicals and non-radical derivatives of oxygen and nitrogen. Reactive oxygen and nitrogen species (RONS) are produced by all aerobic cells and play an important role in aging as well as age-related diseases. Lipid peroxidation is a process of oxidative degradation of lipids that process by which free radicals bind to lipid electrons in the cell membrane resulting in direct cell damage. Lipid peroxidation can cause cellular damage in several ways such as impairing the integrity of the plasma membrane and subcellular organelles by peroxidation, “chain reaction” of ROS production, and activation of phospholipase A2 (PLA2) caused by lipid peroxidation. Fatty acids and other PLA2 metabolites (such as lysophospholipids) are known to damage cell membranes. In the development of kidney damage, the process of lipid peroxidation plays an important role. This is presumably due to the large number of long-chain polyunsaturated fatty acids (PUFAs) in the lipid composition of the kidneys and there are substantial evidence to suggest that ROS is involved in the ischemic, toxic, and immunologically mediated pathogenesis of renal injury, but the cellular mechanisms that result in cell injury and death are still being studied.

Cellular Senescence in Kidney Fibrosis: Pathologic Significance and Therapeutic Strategies

Age-related disorders such as chronic kidney disease (CKD) are increasingly prevalent globally and pose unprecedented challenges. In many aspects, CKD can be viewed as a state of accelerated and premature aging. Aging kidney and CKD share many common characteristic features with increased cellular senescence, a conserved program characterized by an irreversible cell cycle arrest with altered transcriptome and secretome. While developmental senescence and acute senescence may positively contribute to the fine-tuning of embryogenesis and injury repair, chronic senescence, when unresolved promptly, plays a crucial role in kidney fibrogenesis and CKD progression. Senescent cells elicit their fibrogenic actions primarily by secreting an assortment of inflammatory and profibrotic factors known as the senescence-associated secretory phenotype (SASP). Increasing evidence indicates that senescent cells could be a promising new target for therapeutic intervention known as senotherapy, which includes depleting senescent cells, modulating SASP and restoration of senescence inhibitors. In this review, we discuss current understanding of the role and mechanism of cellular senescence in kidney fibrosis. We also highlight potential options of targeting senescent cells for the treatment of CKD.

The Effect of Giving Dadih on Manganese Superoxide Dismutase Gene Expression and Malondialdehyde Levels at Aging Kidney

BACKGROUND: The aging process is a complex physiological mechanism that cannot be disclosed in exact detail. Various theories about the aging process have been put forward by many experts. AIM: This study aims to prove the effect of dadih on manganese superoxide dismutase (MnSOD) gene expression and malondialdehyde levels at aging kidney. MATERIALS AND METHODS: This study used 30 Rattus norvegicus which were divided into three groups: Group 1 was a positive control (did not get dadih), Group 2 received dadih 1 × 4.5 g/day, and Group 3 received dadih 2 × 4.5 g/day for 42 days. After that, MDA levels of kidney tissue are examined using the thiobarbituric acid reactive substances examination technique and examination of kidney and examination of MnSOD was done by immunohistochemical staining of kidney tissue. Data were analyzed using the normality test with Shapiro-Wilk. RESULTS: The results showed that dadih were be able to decreased MDA levels in Group 2 and Group 3 compared to Group 1 (control) 0.97 ± 0.06 pg/mL to 0.75 ± 0.03 (p < 0.05). Dadih also increased MnSOD expression sequentially from Group 1 33.66 ± 9.29 to Group 2 53.58 ± 8.51 and Group 3 73.70 ± 4.29 (p < 0.05) CONCLUSION: This study concluded that dadih can reduce MDA levels in old kidney tissue and dadih can increase the expression of MnSOD.