Genomic profile of Toll-like receptor pathways in traumatically brain-injured mice: effect of exogenous progesterone

Abstract

BackgroundTraumatic brain injury (TBI) causes acute inflammatory responses that result in an enduring cascade of secondary neuronal loss and behavioral impairments. It has been reported that progesterone (PROG) can inhibit the increase of some inflammatory cytokines and inflammation-related factors induced by TBI. Toll-like receptors (TLRs) play a critical role in the induction and regulation of immune/inflammatory responses. Therefore, in the present study, we examined the genomic profiles of TLR-mediated pathways in traumatically injured brain and PROG's effects on these genes.MethodsBilateral cortical impact injury to the medial frontal cortex was induced in C57BL/6J mice. PROG was injected (i.p., 16 mg/kg body weight) at 1 and 6 h after surgery. Twenty-four hours post-surgery, mice were killed and peri-contusional brain tissue was harvested for genomic detection and protein measurement. RT-PCR arrays were used to measure the mRNA of 84 genes in TLR-mediated pathways. Western blot, ELISA and immunohistochemistry were used to confirm the protein expression of genes of interest.ResultsWe found that 2 TLRs (TLR1 and 2), 5 adaptor/interacting proteins (CD14, MD-1, HSPA1a, PGRP and Ticam2) and 13 target genes (Ccl2, Csf3, IL1a, IL1b, IL1r1, IL6, IL-10, TNFa, Tnfrsf1a, Cebpb, Clec4e, Ptgs2 and Cxcl10) were significantly up-regulated after injury. Administration of PROG significantly down-regulated three of the 13 increased target genes after TBI (Ccl-2, IL-1b and Cxcl-10), but did not inhibit the expression of any of the detected TLRs and adaptor/interacting proteins. Rather, PROG up-regulated the expression of one TLR (TLR9), 5 adaptor/interacting proteins, 5 effectors and 10 downstream target genes. We confirmed that Ccl-2, Cxcl-10, TLR2 and TLR9 proteins were expressed in brain tissue, a finding consistent with our observations of mRNA expression.ConclusionThe results demonstrate that TBI can increase gene expression in TLR-mediated pathways. PROG does not down-regulate the increased TLRs or their adaptor proteins in traumatically injured brain. Reduction of the observed inflammatory cytokines by PROG does not appear to be the result of inhibiting TLRs or their adaptors in the acute stage of TBI.

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

“…Time-course analyses show a peak in C/EBPβ and C/EBPδ mRNA upregulation 24 h after focal cerebral ischemia (Kapadia et al 2006) or traumatic brain injury (Sandhir and Berman 2010). The increase 24 h post-insult has been replicated in many studies (Choi et al 2009;Hua et al 2011;Ridder et al 2009;Tureyen et al 2007;von Gertten et al 2005). Increased C/EBPβ and C/EBPδ mRNA levels have also been reported to occur early in areas of lesion after traumatic brain injury (Oliva et al 2012) or exposure to carbonyl sulphide, a gas that produces highly reproducible neurotoxicity in the rat CNS, particularly in the posterior colliculus (Morrison et al 2009).…”

TLR1 expression in mouse brain was increased in a KA-induced seizure model

“…TLR recognition of these endogenous molecules may be involved in the inflammatory response during ''sterile'' tissue damage [10], and the signaling outcomes appear to differ between MAMP-and DAMPinduced TLR activation, which is likely due to the balance requirement between immune intervention and tissue damage repair [25]. Another study using genomic profiles demonstrated that TLR1 was significantly upregulated in traumatically brain-injured mice [26]. In this study, we used an animal model of seizures generated by an intracerebroventricular injection of KA, which is the most popular model of temporal lobe epilepsy and has similar clinical and pathological features to human TLE [27].…”

The Involvement of Cholesterol in Sepsis and Tolerance to Lipopolysaccharide Highlighted by the Transcriptome Analysis of Zebrafish (Danio rerio)

“…In addition to IL1B or TNFB, other proinflammatory genes were modulated after the LPS treatment: the CCAAT/ enhancer binding protein (C/EBP), beta (CEBPB) (at 6 dpf), which is known as a key modulator in inflammatory diseases [28][29][30] ; the glutaminyl-peptide cyclotransferase-like (QPCTL) was the most up-modulated gene in the 4-dpf LDexposed fish (fold change of 8.3) and have been reported to be involved in several inflammatory processes, such as Alzheimer's disease 31 or monocyte migration. 32,33 The elevated expression levels of all these molecules explain the exaggerated inflammation response that characterizes septic shock.…”