The Effect of Rev-erbα Agonist SR9011 on the Immune Response and Cell Metabolism of Microglia

Abstract

Microglia are the immune cells of the brain. Hyperactivation of microglia contributes to the pathology of metabolic and neuroinflammatory diseases. Evidence has emerged that links the circadian clock, cellular metabolism, and immune activity in microglia. Rev-erb nuclear receptors are known for their regulatory role in both the molecular clock and cell metabolism, and have recently been found to play an important role in neuroinflammation. The Rev-erbα agonist SR9011 disrupts circadian rhythm by altering intracellular clock machinery. However, the exact role of Rev-erbα in microglial immunometabolism remains to be elucidated. In the current study, we explored whether SR9011 also had such a detrimental impact on microglial immunometabolic functions. Primary microglia were isolated from 1-3 days old Sprague-Dawley rat pups. The expression of clock genes, cytokines and metabolic genes was evaluated using RT-PCR and rhythmic expression was analyzed. Phagocytic activity was determined by the uptake capacity of fluorescent microspheres. Mitochondria function was evaluated by measuring oxygen consumption rate and extracellular acidification rate. We found that key cytokines and metabolic genes are rhythmically expressed in microglia. SR9011 disturbed rhythmic expression of clock genes in microglia. Pro-inflammatory cytokine expression was attenuated by SR9011 during an immune challenge by TNFα, while expression of the anti-inflammatory cytokine Il10 was stimulated. Moreover, SR9011 decreased phagocytic activity, mitochondrial respiration, ATP production, and metabolic gene expression. Our study highlights the link between the intrinsic clock and immunometabolism of microglia. We show that Rev-erbα is implicated in both metabolic homeostasis and the inflammatory responses in microglia, which has important implications for the treatment of metabolic and neuroinflammatory diseases.

Microglia and the Aging Brain: Are Geriatric Microglia Linked to Poor Sleep Quality?

“…Similarly, genetic or pharmacological suppression of REV-ERBα in microglial cells showed decreased uptake and clearance of Aβ [61]. Administration of the REV-ERBα agonist, SR9011, decreased the inflammatory response of primary microglia [62]. REV-ERBs contribute to a negative feedback loop of the cellular clock repressing a subset of inflammatory genes in a signal-dependent manner by inhibiting enhancer-specific transcription [63].…”

Circadian Clock Regulates Inflammation and the Development of Neurodegeneration

“…Agonist-GSK4112 LPS Decreased IL-6 in human MDMs, primary alveolar macrophages, and THP-1 cells; Reduced Cxcl11, Cxcl6, Il19, and Il10 in human MDMs (Gibbs et al, 2012) REV-ERB Agonist-GSK4112/ Hemin LPS Reduced Il6 in THP-1 (Raghuram et al, 2007;Gibbs et al, 2012) REV-ERBa Antagonist-SR8278 viral-induced encephalitis Reduced survival rate in mice; Increased CCL2 expression (Gagnidze et al, 2016) REV-ERBa Antagonist-GSK1362 LPS Reduced Il6, Ccl2, and G-csf in alveolar macrophages and decreased Il6 expression in BMDMs (Pariollaud et al, 2018) RORa and RORg Agonists-SR100, ursolic acid, SR2211, SR1555, or ML209 / Inhibited development of Th17 cells and reduced inflammatory gene expression (Kojetin and Burris, 2014) REV-ERBa Agonist-GSK4112/ SR9011 LPS Inhibited microglial activation and reduced iNOS and COX-2 secretion and Il6 and Tnfa expression Guo et al, 2019) REV-ERBa Agonist-SR9011 / Reduced phagocytosis, mitochondrial respiration, energy production, and metabolic-related gene expression in primary microglia (Wolff et al, 2020) REV-ERBa Agonist-SR9011 TNFa Decreased Tnfa, Il6, Ccl2, and Il1b, and increased Il10 in primary microglia (Wolff et al, 2020) REV-ERBa Agonist-SR9009 LPS+ATP Suppressed IL-1b and Il6 expression in primary microglia (Griffin et al, 2019a) REV-ERBa Agonist-SR9009 LPS Reduced Il6, Tnfa, and Il1b in primary astrocyte (Griffin et al, 2019a) REV-ERBa Agonist-SR9009 LPS Reduced Il6 and Ccl2 in hippocampus (Griffin et al, 2019a) REV-ERBa Agonist-SR9011, SR9009, and SR10067 / Increased wakefulness and reduced sleep and anxiety-like behavior in mice (Banerjee et al, 2014) REV-ERBa Antagonist-SR8278 / Induced Mania-like behavior (Chung et al, 2014) REV-ERBa Antagonist-SR8278 fAb1-42 Enhanced microglial phagocytosis and increased fAb1-42 uptake by BV-2 cells (Lee et al, 2020) regulated by circadian clocks. Circadian disruption leads to immune dysfunction and neurodegeneration.…”

“…Rev-erbα deficient microglia reveal pro-inflammatory phenotypes and elevated NF-kB activation via binding to the promoter regions of related genes; global deletion of Rev-erbα leads to hippocampal microgliosis and neuronal damage in mice ( Griffin et al., 2019a ). Pharmacologic activation of Rev-erbα inhibits TNFα or LPS-induced pro-inflammatory cytokine expression ( Griffin et al., 2019a ; Wolff et al., 2020 ). Furthermore, astrocytes are also involved in innate immunity in the brain and secrete inflammatory mediators.…”

“…Besides, REV-ERBα agonists-GSK4112 and SR9011 suppress microglial activation, reduce iNOS and COX-2 secretion, and transcription of Il6 and Tnf α, which may be mediated by repression of nuclear factor kappa B (NF-κB) pathway in LPS-treated microglial cells ( Nakazato et al., 2017 ; Guo et al., 2019 ). Moreover, SR9011 reduces phagocytosis, mitochondrial respiration, energy production, and metabolic-related gene expression in primary microglial cells; while under TNFα stimulation, SR9011 decreases the transcripts of Tnf α, Il6 , Ccl2 , and Il1 β, and increases the expression of Il10 in primary microglia ( Wolff et al., 2020 ). Activation of Rev-erbα with agonist-SR9009 suppresses IL-1β secretion and Il6 mRNA expression in primary microglial cells under LPS combined with ATP stimulation, and also significantly reduces the gene expression of Il6 , Tnfa , and Il1b in LPS-induced primary astrocytes ( Griffin et al., 2019a ).…”

Ischemic Stroke and Sleep: The Linking Genetic Factors

“…Moreover, in the experiment, Rev‐erbα regulates mitochondrial function and protects cells against oxidative and environmental stress by upregulating antioxidant enzymes (FoxO1, MnSOD, Hmox1, and catalase) and decreasing ROS production [ 62 ]. These effects can be involved in inflammatory response of microglia [ 63 ], neuroprotection, and brain recovery after acute damage. However, the evidence regarding the role of Rev‐erbα and RORα in stroke is lacking.…”