Melatonin up‐regulates bone marrow mesenchymal stem cells osteogenic action but suppresses their mediated osteoclastogenesis via MT₂‐inactivated NF‐κB pathway

Abstract

Background and Purpose: Melatonin is a neurohormone involved in bone homeostasis. Melatonin directs bone remodelling and the role of bone marrow mesenchymal stem cells (BMMSCs) in the regulating melatonin-mediated bone formationresorption balance remains undefined. Experimental Approach: Osteoporosis models were established and bone tissue and serum were collected to test the effects of melatonin on bone homeostasis. Melatonin receptors were knocked down, the NF-κB signalling pathway and receptor activator of NF-κB ligand (RANKL) expression were investigated. Communication between bone marrow mesenchymal stem cells and osteoclasts was detected with directcontact or indirect-contact system. Key Results: Bone loss and microstructure disorder in mice were reversed after melatonin treatment, as a result of anabolic and anti-resorptive effects. In vitro, a physiological (low) concentration of melatonin promoted the bone marrow mesenchymal stem cells, osteogenic lineage commitment and extracellular mineralization but had no impact on extracellular matrix synthesis. After MT knockdown, especially MT 2 , the positive effects of melatonin on osteogenesis were attenuated. The canonical NF-κB signalling pathway was the first discovered downstream signalling pathway after MT receptor activation and was found to be down-regulated by melatonin during osteogenesis. Melatonin suppressed BMMSC-mediated osteoclastogenesis by inhibiting RANKL production in BMMSCs and this effect only occurred when BMMSCs and osteoclast precursors were co-cultured in an indirect-contact manner. Conclusion and Implications: Our work suggests that melatonin plays a crucial role in bone balance, significantly accelerates the osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing the MT 2 -dependent NF-κB signalling pathway, and down-regulates osteoclastogenesis via RANKL paracrine secretion. Abbreviations: ALP, alkaline phosphatase; BMD, bone mineral density; BMMs, bone marrow monocytes; BMMSCs, bone marrow mesenchymal stem cells; BV/TV, trabecular bone volume per total volume; Col-I, collagen I; CTX-I, C-terminal telopeptide α1 chain of type I collagen; H&E, haematoxylin and eosin; Mel, melatonin; OCN, osteocalcin; OPG, osteoprotegerin; OVX, ovariectomy; PINP, N-terminal propeptide of type I procollagen; RANK, receptor activator of NF-κB; RANKL, receptor activator of NF-κB ligand; TRAP, tartrate-resistant acid phosphatase; Tb. N, trabecular bone number; Tb. Sp, trabecular bone separation; Tb. Th, trabecular bone thickness; μCT, micro-CT.

Melatonin Act as an Antidepressant via Attenuation of Neuroinflammation by Targeting Sirt1/Nrf2/HO-1 Signaling

“…Recently it has been demonstrated that melatonin acts through the Nrf2 pathway and prevents the decline of antioxidant enzyme activities during brain pathological conditions (Moezi et al, 2011;Mendez-David et al, 2015;Herrera-Arozamena et al, 2020;Zhi W. et al, 2020), supporting our results that endogenous melatonin counterbalances the oxidative stress by boosting the body antioxidants system via its receptors. Our results are also in agreement with growing evidence that melatonin enhances HO-1 expression via NF-κB, p38 MAPK, and Nrf2 cascade signaling mechanism (Santofimia-Castaño et al, 2015;Yu et al, 2017;Shah et al, 2017;Ma et al, 2018;Zhao et al, 2018;Rehman et al, 2019;Xi et al, 2019;García et al, 2020;Hein et al, 2020;Zhou et al, 2020;Zhi W. et al, 2020).…”

Melatonin effects on bone: Implications for use as a therapy for managing bone loss

“…86 Melatonin can perform its function independent of melatonin receptors [26][27][28][29][30] or by binding to its two cognate G-protein-coupled receptors, MT1 and MT2, which are widely distributed throughout bodily tissues and cells, 15,[18][19][20][21][22][23] including both osteoblasts and osteoclasts 34 and in the mitochondria. 22,23 Melatonin's bone-favoring effects in aging women may be explained by its stimulatory effects on osteoblasts, 36,51,[65][66][67]119,[139][140][141][142][143][144][145] and inhibitory effects on osteoclasts [146][147][148][149][150][151][152] through MT2 melatonin receptor pathway. 36,66,119,153 Support for melatonin's bone-protective actions have been demonstrated in rodent models where melatonin either modified endogenously by pinealectomy [154][155][156][157]…”

Recent Advances of Osterix Transcription Factor in Osteoblast Differentiation and Bone Formation

“…Furthermore, the occupancy of Osx at the promoter of the Bsp gene is also enhanced by melatonin. Researchers believe that melatonin may be a potent osteogenic agent in the treatment of osteoporosis ( Machida et al, 2006 ; Han et al, 2017 ; Choi et al, 2018 ; Zhou et al, 2020 ). Another hormone neuropeptide Y, produced by osteoblasts and other peripheral tissues, was also proved to directly promote osteogenic differentiation of MC3T3-E1 cells by upregulating Osx in vitro ( Zhang B. et al, 2020 ).…”