Autophagy protects mitochondrial health in heart failure

Myocardial ischemia-reperfusion injury: The balance mechanism between mitophagy and NLRP3 inflammasome

Myocardial ischemia-reperfusion injury (MIRI) is an injury to cardiomyocytes due to restoration of blood flow after myocardial infarction (MI). It has recently gained much attention in clinical research with special emphasis on the roles of mitochondrial autophagy and inflammation. A mild inflammatory response promotes recovery of post-ischemic cardiomyocyte function and vascular regeneration, but a severe inflammatory response can cause irreversible and substantial cellular damage. Similarly, moderate mitochondrial autophagy can help inhibit excessive inflammation and protect cardiomyocytes. However, MIRI is aggravated when mitochondrial function is disrupted, such as inadequate clearance of damaged mitochondria or excessive activation of mitophagy. How to moderately control mitochondrial autophagy while promoting its balance with nucleotide-binding oligomerization structural domain receptor protein 3 (NLRP3) inflammasome activation is critical. In this paper, we reviewed the molecular mechanisms of mitochondrial autophagy and NLRP3 inflammasome, described the interaction between NLRP3 inflammasome and mitochondrial autophagy, and the effects of different signaling pathways and molecular proteins on MIRI, to provide a reference for future research.

Selenomethionine supplementation mitigates fluoride-induced liver apoptosis and inflammatory reactions by blocking Parkin-mediated mitophagy in mice

As an environmental pollutant, fluoride-induced liver damage is directly linked to mitochondrial alteration and oxidative stress. Selenium's antioxidant capacity has been shown to alleviate liver damage. Emerging research proves that E3 ubiquitin ligase Park2 (Parkin)-mediated mitophagy may be a therapeutic target for fluorosis. The current study explored the effect of diverse selenium sources on fluoride-caused liver injury and the role of Parkin-mediated mitophagy in this intervention process. Therefore, this study established a fluoride-different selenium sources co-intervention wild-type (WT) mouse model and a fluoride-optimum selenium sources co-intervention Parkin gene knockout (Parkin-/-) mouse model. Our results show that selenomethionine (SeMet) is the optimum selenium supplementation form for mice suffering from fluorosis when compared to sodium selenite and chitosan nano‑selenium because mice from the F-SeMet group showed more closely normal growth and development levels of liver function, antioxidant capacity, and anti-inflammatory ability. Explicitly, SeMet ameliorated liver inflammation and cell apoptosis in fluoride-toxic mice, accomplished through downregulating the mRNA and protein expression levels associated with mitochondrial fusion and fission, mitophagy, apoptosis, inflammatory signalling pathway of nuclear factor-kappa B (NF-κB), reducing the protein expression levels of PARKIN, PTEN-induced putative kinase1 (PINK1), SQSTM1/p62 (P62), microtubule-associated protein light chain 3 (LC3), cysteinyl aspartate specific proteinase 3 (CASPAS3), as well as restraining the content of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), and interferon-γ (IFN-γ). The Parkin-/- showed comparable positive effects to the SeMet in the liver of fluorosis mice. The structure of the mitochondria, mRNA, protein expression levels, and the content of proinflammatory factors in mice from the FParkin-/- and F + SeMetParkin-/- groups closely resembled those in the F + SeMetWT group. Overall, the above results indicated that SeMet could alleviate fluoride-triggered inflammation and apoptosis in mice liver via blocking Parkin-mediated mitophagy.

Nur77 improves ovarian function in reproductive aging mice by activating mitophagy and inhibiting apoptosis

Reproductive aging not only affects the fertility and physical and mental health of women but also accelerates the aging process of other organs. There is an urgent need newfor novel mechanisms, targets, and drugs to break the vicious cycle of mitochondrial dysfunction, redox imbalance, and germ cell apoptosis associated with ovarian aging. Autophagy, recognized as a longevity mechanism, has recently become a focal point in anti-aging research. Although mitophagy is a type of autophagy, its role and regulatory mechanisms in ovarian aging, particularly in age-related ovarian function decline, remain unclear. Nerve growth factor inducible gene B (Nur77) is an early response gene that can be stimulated by oxidative stress, DNA damage, metabolism, and inflammation. Recent evidence recommends that decreased expression of Nur77 is associated with age-related myocardial fibrosis, renal dysfunction, and Parkinson's disease; however, its association with ovarian aging has not been studied yet. We herein identified Nur77 as a regulator of germ cell senescence, apoptosis, and mitophagy and found that overexpression of Nur77 can activate mitophagy, improve oxidative stress, reduce apoptosis, and ultimately enhance ovarian reserve in aged mice ovaries. Furthermore, we discovered an association between Nur77 and the AKT pathway through String and molecular docking analyses. Experimental confirmation revealed that the AKT/mTOR signaling pathway is involved in the regulation of Nur77 in ovarian function. In conclusion, our results suggest Nur77 as a promising target for preventing and treating ovarian function decline related to reproductive aging.

Molecular and Cellular Mechanisms Underlying the Cardiac Hypertrophic and Pro-Remodelling Effects of Leptin

Since its initial discovery in 1994, the adipokine leptin has received extensive interest as an important satiety factor and regulator of energy expenditure. Although produced primarily by white adipocytes, leptin can be synthesized by numerous tissues including those comprising the cardiovascular system. Cardiovascular function can thus be affected by locally produced leptin via an autocrine or paracrine manner but also by circulating leptin. Leptin exerts its effects by binding to and activating specific receptors, termed ObRs or LepRs, belonging to the Class I cytokine family of receptors of which six isoforms have been identified. Although all ObRs have identical intracellular domains, they differ substantially in length in terms of their extracellular domains, which determine their ability to activate cell signalling pathways. The most important of these receptors in terms of biological effects of leptin is the so-called long form (ObRb), which possesses the complete intracellular domain linked to full cell signalling processes. The heart has been shown to express ObRb as well as to produce leptin. Leptin exerts numerous cardiac effects including the development of hypertrophy likely through a number of cell signaling processes as well as mitochondrial dynamics, thus demonstrating substantial complex underlying mechanisms. Here, we discuss mechanisms that potentially mediate leptin-induced cardiac pathological hypertrophy, which may contribute to the development of heart failure.