The Impact of Melatonin Supplementation and NLRP3 Inflammasome Deletion on Age-Accompanied Cardiac Damage

This study was partially supported by grants from the Instituto de Salud Carlos III through the projects PI13-981, PI16-00519, PI19-01372, and CB/10/00238 (Co-funded by European Regional Development Fund/European Social Fund "Investing in your future"); the Conserjeria de Economia, Innovacion, Ciencia y Empleo, Junta de Andalucia (CTS-101), Spain, and also by Sohag University, Egypt. M.F.-O and J.F.-M are supported by a FPU fellowship from the Ministerio de Educacion, Spain.To investigate the role of NLRP3 inflammasome in cardiac aging, we evaluate here morphological and ultrastructural age-related changes of cardiac muscles fibers in wild-type and NLRP3-knockout mice, as well as studying the beneficial effect of melatonin therapy. The results clarified the beginning of the cardiac sarcopenia at the age of 12 months, with hypertrophy of cardiac myocytes, increased expression of beta-MHC, appearance of small necrotic fibers, decline of cadiomyocyte number, destruction of mitochondrial cristae, appearance of small-sized residual bodies, and increased apoptotic nuclei ratio. These changes were progressed in the cardiac myocytes of 24 old mice, accompanied by excessive collagen deposition, higher expressions of IL-1 alpha, IL-6, and TNF alpha, complete mitochondrial vacuolation and damage, myofibrils disorganization, multivesicular bodies formation, and nuclear fragmentation. Interestingly, cardiac myocytes of NLRP3(-/-) mice showed less detectable age-related changes compared with WT mice. Oral melatonin therapy preserved the normal cardiomyocytes structure, restored cardiomyocytes number, and reduced beta-MHC expression of cardiac hypertrophy. In addition, melatonin recovered mitochondrial architecture, reduced apoptosis and multivesicular bodies' formation, and decreased expressions of beta-MHC, IL-1 alpha, and IL-6. Fewer cardiac sarcopenic changes and highly remarkable protective effects of melatonin treatment detected in aged cardiomyocytes of NLRP3(-/-) mice compared with aged WT animals, confirming implication of the NLRP3 inflammasome in cardiac aging. Thus, NLRP3 suppression and melatonin therapy may be therapeutic approaches for age-related cardiac sarcopenia.Instituto de Salud Carlos III (European Regional Development Fund/European Social Fund "Investing in your future") PI13-981 PI16-00519 PI19-01372 CB/10/00238Junta de Andalucia CTS-101Sohag UniversityGerman Research Foundation (DFG

The Protective Effect of Melatonin Against Age-Associated, Sarcopenia-Dependent Tubular Aggregate Formation, Lactate Depletion, and Mitochondrial Changes.

To gain insight into the mechanism of sarcopenia and the protective effect of melatonin, the gastrocnemius muscles of young (3-4 months), early-aged (12 months), and old-aged (24 months) wild-type C57BL/6J female mice were examined by magnetic resonance and microscopy. Locomotor activity, lactate production, and nuclear apoptosis were also assessed. The results support the early onset of sarcopenia at 12 months of age, with reduction of muscle fiber number, muscle weight/body weight ratio, lactate, and locomotor activity. Lipid droplet infiltration and autophagosomes were also detected. These changes driven little effects on the early-aged muscle, but they got worse in old-aged animals by the progressive damage of the muscle. Old-aged muscle showed a reduction of the mitochondrial number, a destruction of the mitochondrial cristae, and swelling. Tubular aggregates and nucleic acid fragmentation were the most striking findings in old-aged muscle, reflecting a broad damage with loss of autophagy efficacy. Oral melatonin administration conserved the normal muscular architecture, weight, muscle fiber number, and activity in the old age; it stimulated lactate production, prevented mitochondrial damage and tubular aggregates, and reduced the percentage of apoptotic nuclei in aged muscles. Altogether, gastrocnemius muscle showed age-mediated signs of sarcopenia that were reduced by melatonin treatment