ABSTRACT
Background: The disruption of the circadian clock is associated with inflammatory and immunological disorders. BMAL2, a critical circadian protein, forms a dimer with CLOCK, activating transcription. Extracellular cold-inducible RNA-binding protein (eCIRP), released during sepsis, can induce macrophage endotoxin tolerance. We hypothesized that eCIRP induces BMAL2 expression and promotes macrophage endotoxin tolerance through triggering receptor expressed on myeloid cells-1 (TREM-1). Methods: C57BL/6 wild-type (WT) male mice were subjected to sepsis by cecal ligation and puncture (CLP). Serum levels of eCIRP 20 h post-CLP were assessed by ELISA. Peritoneal macrophages (PerM) were treated with recombinant mouse (rm) CIRP (eCIRP) at various doses for 24 h. The cells were then stimulated with LPS for 5 h. The levels of TNF-α and IL-6 in the culture supernatants were assessed by ELISA. PerM were treated with eCIRP for 24 h, and the expression of PD-L1, IL-10, STAT3, TREM-1 and circadian genes such as BMAL2, CRY1, and PER2 was assessed by qPCR. Effect of TREM-1 on eCIRP-induced PerM endotoxin tolerance and PD-L1, IL-10, and STAT3 expression was determined by qPCR using PerM from TREM-1-/- mice. Circadian gene expression profiles in eCIRP-treated macrophages were determined by PCR array and confirmed by qPCR. Induction of BMAL2 activation in bone marrow-derived macrophages was performed by transfection of BMAL2 CRISPR activation plasmid. The interaction of BMAL2 in the PD-L1 promoter was determined by computational modeling and confirmed by the BIAcore assay. Results: Serum levels of eCIRP were increased in septic mice compared to sham mice. Macrophages pre-treated with eCIRP exhibited reduced TNFα and IL-6 release upon LPS challenge, indicating macrophage endotoxin tolerance. Additionally, eCIRP increased the expression of PD-L1, IL-10, and STAT3, markers of immune tolerance. Interestingly, TREM-1 deficiency reversed eCIRP-induced macrophage endotoxin tolerance and significantly decreased PD-L1, IL-10, and STAT3 expression. PCR array screening of circadian clock genes in peritoneal macrophages treated with eCIRP revealed the elevated expression of BMAL2, CRY1, and PER2. In eCIRP-treated macrophages, TREM-1 deficiency prevented the upregulation of these circadian genes. In macrophages, inducible BMAL2 expression correlated with increased PD-L1 expression. In septic human patients, blood monocytes exhibited increased expression of BMAL2 and PD-L1 in comparison to healthy subjects. Computational modeling and BIAcore assay identified a putative binding region of BMAL2 in the PD-L1 promoter, suggesting BMAL2 positively regulates PD-L1 expression in macrophages. Conclusion: eCIRP upregulates BMAL2 expression via TREM-1, leading to macrophage endotoxin tolerance in sepsis. Targeting eCIRP to maintain circadian rhythm may correct endotoxin tolerance and enhance host resistance to bacterial infection.
Subject(s)
RNA-Binding Proteins , Sepsis , Animals , Humans , Male , Mice , ARNTL Transcription Factors/genetics , Disease Models, Animal , Endotoxins/immunology , Immune Tolerance , Lipopolysaccharides/immunology , Macrophages/immunology , Macrophages/metabolism , Macrophages, Peritoneal/immunology , Macrophages, Peritoneal/metabolism , Mice, Inbred C57BL , Mice, Knockout , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Sepsis/immunology , Sepsis/metabolism , Triggering Receptor Expressed on Myeloid Cells-1/immunology , Triggering Receptor Expressed on Myeloid Cells-1/genetics , Triggering Receptor Expressed on Myeloid Cells-1/metabolismABSTRACT
Marine mammals, especially cetaceans, have evolved a very special form of sleep characterized by unihemispheric slow-wave sleep (USWS) and a negligible amount or complete absence of rapid-eye-movement sleep; however, the underlying genetic mechanisms remain unclear. Here, we detected unique, significant selection signatures in basic helix-loop-helix ARNT like 2 (BMAL2; also called ARNTL2), a key circadian regulator, in marine mammal lineages, and identified two nonsynonymous amino acid substitutions (K204E and K346Q) in the important PER-ARNT-SIM domain of cetacean BMAL2 via sequence comparison with other mammals. In vitro assays revealed that these cetacean-specific mutations specifically enhanced the response to E-box-like enhancer and consequently promoted the transcriptional activation of PER2, which is closely linked to sleep regulation. The increased PER2 expression, which was further confirmed both in vitro and in vivo, is beneficial for allowing cetaceans to maintain continuous movement and alertness during sleep. Concordantly, the locomotor activities of zebrafish overexpressing the cetacean-specific mutant bmal2 were significantly higher than the zebrafish overexpressing the wild-type gene. Subsequently, transcriptome analyses revealed that cetacean-specific mutations caused the upregulation of arousal-related genes and the downregulation of several sleep-promoting genes, which is consistent with the need to maintain hemispheric arousal during USWS. Our findings suggest a potential close relationship between adaptive changes in BMAL2 and the remarkable adaptation of USWS and may provide novel insights into the genetic basis of the evolution of animal sleep.
Subject(s)
ARNTL Transcription Factors , Cetacea , Sleep, Slow-Wave , Animals , Locomotion/genetics , Mammals , Sleep/genetics , Sleep, Slow-Wave/genetics , Zebrafish , ARNTL Transcription Factors/genetics , ARNTL Transcription Factors/metabolism , Cetacea/geneticsABSTRACT
Objective To study the expression of clock genes in Parkinson's disease(PD) and also the molecular clock machinery of PD.Methods Seventeen PD patients(nine men,eight women)and sixteen agematched controls(nine men,seven women) were investigated in this study.Bload samples were collected over a 12h span at 21:00,00:00,06:00 and 09:00.Using a real-time PCR assay,the peripheral molecular clock was examined by measuring Bmall and Bmal2 expression in total leukocytes during the dark span(from 21:00 to 09:00)in PD patients and age-matched healthy controls.Results At PD,the relative abundance of Bmall was significantly lower at 21:00,00:00 and 06:00(21:00:(22.17±4.09)vs(51.14±8.31),P=0.003,00:00:(30.30±5.45)vs(100.00±24.71),P=0.008,06:00:(19.02±3.33)vs(65.61±14.11),P=0.002).The relative Bmal2 levels in PD patients were significantly less abundant than controls at 21:00 and 00:00(21:00:(48.09±7.40)vs(84.96±9.34),P=0.005;00:00:((65.85±7.88)vs(100.00±11.78),P=0.025).Conclusion These results suggest that a peripheral molecular clock is altered in PD patients.In addition,the relative abundance of Bmall and Bmal2 was significantly lower in PD patients versus control subjects,which can provide a molecular basis to help monitor disease progression and response to investigational drugs.
