MicroRNA-433 Dampens Glucocorticoid Receptor Signaling, Impacting Circadian Rhythm and Osteoblastic Gene Expression

Abstract

Serum glucocorticoids play a critical role in synchronizing circadian rhythm in peripheral tissues, and multiple mechanisms regulate tissue sensitivity to glucocorticoids. In the skeleton, circadian rhythm helps coordinate bone formation and resorption. Circadian rhythm is regulated through transcriptional and post-transcriptional feedback loops that include microRNAs . How microRNAs regulate circadian rhythm in bone is unexplored. We show that in mouse calvaria, miR-433 displays robust circadian rhythm, peaking just after dark. In C3H/10T1/2 cells synchronized with a pulse of dexamethasone, inhibition of miR-433 using a tough decoy altered the period and amplitude of Per2 gene expression, suggesting that miR-433 regulates rhythm. Although miR-433 does not directly target the Per2 3-UTR, it does target two rhythmically expressed genes in calvaria, Igf1 and Hif1␣. miR-433 can target the glucocorticoid receptor; however, glucocorticoid receptor protein abundance was unaffected in miR-433 decoy cells. Rather, miR-433 inhibition dramatically enhanced glucocorticoid signaling due to increased nuclear receptor translocation, activating glucocorticoid receptor transcriptional targets. Last, in calvaria of transgenic mice expressing a miR-433 decoy in osteoblastic cells (Col3.6 promoter), the amplitude of Per2 and Bmal1 mRNA rhythm was increased, confirming that miR-433 regulates circadian rhythm. miR-433 was previously shown to target Runx2, and mRNA for Runx2 and its downstream target, osteocalcin, were also increased in miR-433 decoy mouse calvaria. We hypothesize that miR-433 helps maintain circadian rhythm in osteoblasts by regulating sensitivity to glucocorticoid receptor signaling.The circadian rhythm is an internal timing mechanism important for orchestrating physiological homeostasis, through synchronizing behavioral and physiological patterns. This coordinates biological processes critical for overall health, such as tissue repair and growth, maintenance of the immune response, and optimization of metabolism. The circadian rhythm is driven by a complex interaction between the hypothalamic suprachiasmatic nucleus (SCN), 4 also known as the central clock, and the peripheral circadian clocks. As the central oscillator, the SCN responds to environmental periodic cues, such as light, eating patterns, and temperature. In response to these cues, the SCN entrains peripheral circadian clocks through stimulation of neural or hormonal signals (e.g. glucocorticoids) to enact their effects on target tissues (1).In the central oscillator and peripheral tissues, the rhythm is maintained locally by clock genes that interact through transcriptional and post-transcriptional feedback loops. The main positive regulators are aryl hydrocarbon receptor nuclear translocator-like (Arntl or Bmal1) and circadian locomotor output cycles kaput (Clock), which are negatively regulated by the period genes (Per1, Per2, and Per3) and the cryptochrome genes (Cry1 and Cry2), among others (for a review, see Ref.2). Bmal1 and Clock form a heterodi...

Extracellular Vesicles: Potential Participants in Circadian Rhythm Synchronization

“…In addition, circulating miR-494 and miR-142-3p can modulate CRs by targeting the clock gene BMAL1 96 , 97 , while miR-433 regulates the expression of PER2 and BMAL1 98 . BMAL1 is also targeted by miR-27b-3p 113 and miR-155 99 , while PER1 is targeted by miR-34a 100 , and the miR-192/194 cluster can inhibit the PER family 101 .…”

Electroacupuncture Alleviates Surgical Trauma-Induced Hypothalamus Pituitary Adrenal Axis Hyperactivity Via microRNA-142

“…Pituitary MicroR-449a (miR-449a) impairment induced a decrease in the level of CRH receptor 1 (CRHR1) level in low-birth-weight rats (Nemoto et al, 2015 ), and miR-449a was involved in the GC induced CRHR1 downregulation (Nemoto et al, 2013 ). GC function was related to miR-338 (Zhang et al, 2016 ) and miR-433 (Smith et al, 2016 ) in osteoclast formation. Hypothalamic miRNAs reportedly played a critical role in energy balance (Schneeberger et al, 2015 ).…”

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“…For instance, knockdown of miR-219 was shown to lengthen the circadian period, whereas a Cry1/Cry2 double knockout abolished the miR-219 rhythm [95]. More information of actions of miRNAs on circadian rhythms has accumulated during the last years [96][97][98][99][100][101], but the complete details would exceed the scope of this article. However, a specific point should be addressed because of its fundamental importance.…”