Heat shock induces HuR-dependent MKP-1 posttranslational regulation through the p38 MAPK signaling cascade.

Previous studies demonstrated that phosphatases play a pivotal role in modulating inflammation-associated signal transduction, particularly in the context of heat shock, where Mitogen-Activated Protein Kinase Phosphatase-1 (MKP-1) appears to have a central role. Recently, Human Antigen R (HuR) has also been identified as a factor that enhances stress-response protein MKP-1 levels. Consequently, we have directed our interest towards elucidating the mechanisms by which heat shock induces MKP-1 mRNA stabilization, dependent on HuR via the p38 MAPK Signaling Cascade. In this study, we subjected Mouse Embryonic Fibroblast (Mef) cells to heat shock treatment, resulting in a potent stabilization MKP-1 mRNA. The RNA-binding protein HuR, known to influence mRNA, was observed to bind to the MKP-1 AU-rich 3 ´untranslated region. Transfection of p38 wild-type Mef cells with a flag-HuR plasmid resulted in a significant increase in MKP-1 mRNA stability. Interestingly, transfection of the siRNA for HuR into Mef cells resulted in diminished MKP-1 mRNA stability following heat shock, inhibition of p38 MAPK activity effectively curtailed heat shock-mediated MKP-1 mRNA stability. Immunofluorescence analyses further revealed that the translocation of HuR was contingent on p38 MAPK Signaling Cascade. Collectively, these findings underscore the regulatory role of heat shock in MKP-1 gene expression at posttranscriptional levels. The mechanisms underlying the observed increased MKP-1 mRNA stability are shown to be partially dependent on HuR through the p38 MAPK Signaling Cascade.

Peripheral Klotho protects the kidney and brain by regulating M2a/M2c macrophage polarization in d-gal-treated aged mice.

In elderly individuals, aging can cause changes in the structure and function of one or more organs, increasing their susceptibility to various damage factors, especially the heart, kidney, brain and other important organs. Therefore, the incidence of cardiovascular disease, neurodegenerative diseases and chronic kidney disease in the elderly population is significantly higher than that in the general population. In our previous study, the hearts of aged mice did not express the antiaging protein Klotho (KL), but peripheral elevation of KL may significantly delay cardiac aging. The kidney and brain are the main organs that produce KL, but the effects and mechanism of peripheral KL supplementation on the kidney and hippocampus are still unclear. To study the effect and possible mechanism of KL against kidney and hippocampus aging, 60 male BALB/c mice were randomly divided into the Adult group, the KL group, the D-gal-induced Aged group, and the KL + Aged group. The results showed that KL increased anti-inflammatory M2a/M2c macrophages in the kidney and hippocampus of aging mice, significantly reduced tissue inflammation and oxidative stress, and improved organ function and aging status. More importantly, we demonstrate that despite the impermeable bloodbrain barrier in mice, peripherally administered KL surprisingly enhances M2-type microglia polarization, induces cognitive enhancement and reduces neuroinflammation. Cellular experimental results suggest that KL may play a role in delaying senescence by regulating the TLR4/Myd88/NF-κB signaling pathway to regulate macrophage polarization and reduce aging-related inflammation and oxidative stress.

Klotho protects against aged myocardial cells by attenuating ferroptosis.

Klotho (KL) is a renal protein with aging-suppression properties that mediates its regulatory effect during cardiac fibroblast aging. However, to determine whether KL can protect aged myocardial cells by attenuating ferroptosis, this study aimed to investigate the protective effect of KL on aged cells and to explore its potential mechanism. Cell injury of H9C2 cells was induced with D-galactose (D-gal) and treated with KL in vitro. This study demonstrated that D-gal induces aging in H9C2 cells. D-gal treatment increased ß-GAL(ß-galactosidase) activity, decreased cell viability, enhanced oxidative stress, reduced mitochondrial cristae, and decreased the expression of solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase-4 (GPx4), and P53, which are primary regulators of ferroptosis. The results showed that KL can eliminate D-gal-induced aging in H9C2 cells, likely due to its ability to increase the expression of the ferroptosis-associated proteins SLC7A11 and GPx4. Moreover, pifithrin-α, a P53-specific inhibitor, enhanced the expression of SLC7A11 and GPx4. These results suggest that KL may be involved in D-gal-induced H9C2 cellular aging during ferroptosis, mainly through the P53/SLC7A11/GPx4 signaling pathway.

The serum soluble Klotho alleviates cardiac aging and regulates M2a/M2c macrophage polarization via inhibiting TLR4/Myd88/NF-κB pathway.

Aging is a continuous and irreversible process that leads to a progressive deterioration in cardiac geometry and function. Klotho is an anti-aging protein with cardioprotective effect. However, the relationship between Klotho and cardiac aging and its possible mechanism are not completely clear. We applied D-galactosamine (D-Gal) to replicate cardiac senescence by increasing oxidative stress in the heart. M2 anti-inflammatory markers in the aging hearts were observed significantly lower than those in adult mice. Therefore, in this study, we demonstrated that serum soluble Klotho (sKL) could exert its cardioprotective and anti-inflammatory effects by regulating the phenotype of macrophages by inhibiting TLR4/MyD88/NF-κB. In terms of mechanism, supplementation of serum soluble Klotho can prevent excessive oxidative stress, inflammation, apoptosis and cardiac dysfunction in the aging heart. In RAW264.7 cells, sKL induced macrophages to differentiate into M2a/M2c macrophages, and the culture supernatant of M2a/M2c macrophages significantly reversed the senescence of cardiomyocytes and improved myocardial viability compared with the control group. Therefore, supplementation of sKL can improve aging cardiac function, reduce cardiac oxidative stress, inflammation and apoptosis by promoting M2a/M2c polarized macrophages via inhibiting the TLR4/Myd88/NF-κB pathway.