Ruohonen, S. | Search bioRxiv

bioRxiv2023

α-Melanocyte-Stimulating Hormone Regulates Pathological Cardiac Remodeling by Activating Melanocortin 5 Receptor in Cardiomyocytes

Background-Melanocyte-stimulating hormone (-MSH) regulates diverse physiological functions by activating melanocortin receptors (MC-R). -MSH is predominantly expressed in the pituitary gland, but it is also found in several peripheral tissues such as the skin and heart. However, the role of -MSH and its possible target receptors in the heart remain completely unknown. Therefore, we sought to investigate whether -MSH could be involved in the regulation of pathological cardiac remodeling. MethodsTissue -MSH concentrations and the effects of chronic -MSH administration were investigated in mice subjected to transverse aortic constriction (TAC). Rat H9c2 cells, neonatal mouse ventricular myocytes and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) were used to study the effects of -MSH and selective MC-R agonists. Inducible cardiomyocyte-specific melanocortin 5 receptor (MC5-R) knockout mouse model was engineered to investigate the role of MC5-R in cardiac hypertrophy. Results-MSH was highly expressed in the mouse heart, particularly in the ventricles, and its level was reduced in the left ventricles of TAC-operated mice. Administration of a stable -MSH analogue protected mice against TAC-induced cardiac hypertrophy and systolic dysfunction. In vitro experiments revealed that cardiomyocytes serve as effector cells for the -MSH mediated antihypertrophic signaling and that selective activation of MC5-R mimics the actions of -MSH. In keeping with these findings, MC5-R was downregulated in the failing mouse heart and stressed hiPSC-CMs. Silencing of MC5-R in mouse cardiomyocytes induced hypertrophy and fibrosis markers in vitro and aggravated TAC-induced cardiac hypertrophy and fibrosis in vivo. Conversely, pharmacological activation of MC5-R improved systolic function and reduced cardiac fibrosis in TAC-operated mice. Conclusions-MSH is expressed in the heart and protects against pathological cardiac remodeling by activating MC5-R in cardiomyocytes. These results suggest that analogues of naturally occurring -MSH, that have been recently approved for clinical use and have agonistic activity at MC5-R, may be of benefit in treating heart failure.

physiology↗

bioRxiv2022

Dissecting the KNDy hypothesis: KNDy neuron-derived kisspeptins are dispensable for puberty but essential for preserved female fertility and gonadotropin pulsatility

Kiss1 neurons in the hypothalamic arcuate-nucleus (ARC) play key roles in the control of GnRH pulsatility and fertility. A fraction of ARC Kiss1 neurons, termed KNDy, co-express neurokinin B (NKB; encoded by Tac2). Yet, NKB- and Kiss1-only neurons are also found in the ARC, while a second major Kiss1-neuronal population is present in the rostral hypothalamus. The specific contribution of different Kiss1 neuron sub-sets to reproductive control remains unfolded. To tease apart the physiological roles of KNDy-born kisspeptins, conditional ablation of Kiss1 in Tac2-expressing cells was implemented in vivo. Mice with Tac2 cell-specific Kiss1 KO (TaKKO) displayed reduced ARC kisspeptin content and Kiss1 expression, with greater suppression in females, which was detectable at infantile-pubertal age. In contrast, Tac2/NKB levels were fully preserved. Despite the drop of ARC Kiss1/kisspeptin, pubertal timing was normal in TaKKO mice of both sexes. However, young-adult TaKKO females displayed disturbed LH pulsatility and sex steroid levels, with suppressed basal LH and pre-ovulatory LH surges, early-onset subfertility and premature ovarian insufficiency. Conversely, testicular histology and fertility were grossly conserved in TaKKO males. Ablation of Kiss1 in Tac2-cells led also to sex-dependent alterations in body composition, glucose homeostasis and locomotor activity. Our data document that KNDy-born kisspeptins are dispensable/compensable for puberty in both sexes, but required for maintenance of female gonadotropin pulsatility and fertility, as well as adult metabolic homeostasis. Significance StatementNeurons in the hypothalamic arcuate nucleus (ARC) co-expressing kisspeptins and NKB, named KNDy, have been recently suggested to play a key role in pulsatile secretion of gonadotropins, and hence reproduction. However, the relative contribution of this Kiss1 neuronal-subset, vs. ARC Kiss1-only and NKB-only neurons, as well as other Kiss1 neuronal populations, has not been assessed in physiological settings. We report here findings in a novel mouse-model with elimination of KNDy-born kisspeptins, without altering other kisspeptin compartments. Our data highlights the heterogeneity of ARC Kiss1 populations and document that, while dispensable/compensable for puberty, KNDy-born kisspeptins are required for proper gonadotropin pulsatility and fertility, specifically in females. Characterization of this functional diversity is especially relevant, considering the potential of kisspeptin-based therapies for management of human reproductive disorders. Disclosure StatementThe authors have nothing to disclose in relation to the contents of this work.

physiology↗