Coupling an activated MAP kinase to circadian clock output

Rhythms in Remodeling: Posttranslational Regulation of Bone by the Circadian Clock

The circadian clock is a fundamental timekeeping system that regulates rhythmic biological processes in response to environmental light-dark cycles. In mammals, core clock genes (CLOCK, BMAL1, PER, and CRY) orchestrate these rhythms through transcriptional-translational feedback loops, influencing various physiological functions, including bone remodeling. Bone homeostasis relies on the coordinated activities of osteoblasts, osteoclasts, and osteocytes, with increasing evidence highlighting the role of circadian regulation in maintaining skeletal integrity. Disruptions in circadian rhythms are linked to bone disorders such as osteoporosis. Posttranslational modifications (PTMs), including phosphorylation, acetylation, and ubiquitination, serve as crucial regulators of both circadian mechanisms and bone metabolism. However, the specific role of PTMs in integrating circadian timing with bone remodeling remains underexplored. This review examines the intersection of circadian regulation and PTMs in bone biology, elucidating their impact on bone cell function and homeostasis. Understanding these interactions may uncover novel therapeutic targets for skeletal diseases associated with circadian disruptions.

Experimental study of effect of corticosterone on primary cultured hippocampal neurons and their Ca2+/CaMKII expression

To explore the effect of different concentrations of corticosterone (CORT) on primary cultured hippocampal neurons and their Ca2+/CaMK II expression and possible mechanism, the changes of hippocampal neurons were observed in terms of morphology, activity of cells, cell death, concentrations of cytosolic free calcium, and the expression of CaMK II by using MTT assay, flow cytometry, fluorescent labeling of Fura-2/AM and Western blotting after 10(-7), 10(-6) and 10(-5) mol/L of CORT was added to culture medium, The evident effect of 10(-6) and 10(-5) mol/L of CORT on the morphology of hippocampal neuron was found. Compared with control neurons, the activity of the cells was markedly decreased and [Ca2+]i increased in the neurons treated with 10(-6) and 10(-5) mol/L of CORT, but no change was observed in the neuron treated with 10(-7) mol/L of CORT. The death was either by way of apoptosis or necrosis in the cells treated with 10(-6) and 10(-5) mol/L of CORT respectively. The correlation analysis showed that a reverse correlation existed between [Ca2+]i and the expression of CaMK II. Either apoptosis or necrosis occurs in the hippocampal neurons treated with CORT. The increased hippocampal [Ca2+]i is both the result of CORT impairing the hippocampal neurons and the cause of the apoptosis of hippocampal neurons and the decreased CaMK II expression.