The innate immune response to coxsackievirus B3 predicts progression to cardiovascular disease and heart failure in male mice

Abstract

BackgroundMen are at an increased risk of dying from heart failure caused by inflammatory heart diseases such as atherosclerosis, myocarditis and dilated cardiomyopathy (DCM). We previously showed that macrophages in the spleen are phenotypically distinct in male compared to female mice at 12 h after infection. This innate immune profile mirrors and predicts the cardiac immune response during acute myocarditis.MethodsIn order to study sex differences in the innate immune response, five male and female BALB/c mice were infected intraperitoneally with coxsackievirus B3 (CVB3) or phosphate buffered saline and their spleens were harvested 12 h later for microarray analysis. Gene expression was determined using an Affymetrix Mouse Gene 1.0 ST Array. Significant gene changes were verified by quantitative real-time polymerase chain reaction or ELISA.ResultsDuring the innate immune response to CVB3 infection, infected males had higher splenic expression of genes which are important in regulating the influx of cholesterol into macrophages, such as phospholipase A2 (PLA2) and the macrophage scavenger receptor compared to the infected females. We also observed a higher expression in infected males compared to infected females of squalene synthase, an enzyme used to generate cholesterol within cells, and Cyp2e1, an enzyme important in metabolizing cholesterol and steroids. Infected males also had decreased levels of the translocator protein 18 kDa (TSPO), which binds PLA2 and is the rate-limiting step for steroidogenesis, as well as decreased expression of the androgen receptor (AR), which indicates receptor activation. Gene differences were not due to increased viral replication, which was unaltered between sexes.ConclusionsWe found that, compared to females, male mice had a greater splenic expression of genes which are important for cholesterol metabolism and activation of the AR at 12 h after infection. Activation of the AR has been linked to increased cardiac hypertrophy, atherosclerosis, myocarditis/DCM and heart failure in male mice and humans.

Biomarkers of Heart Failure in Myocarditis and Dilated Cardiomyopathy

“…The importance of TLR4 signaling in a strictly autoimmune model of myocarditis was demonstrated by Nishikubo et al where TLR4 signaling was found to be necessary to mount a Th1-type immune response (Nishikubo et al, 2007). We have shown that TLR4 is upregulated on macrophages and mast cells during the innate immune response to CVB3 and during acute CVB3 myocarditis and this response results in increased inflammation and progression to DCM and HF in males compared to females (Frisancho-Kiss et al, 2007;Onyimba et al, 2011). A Th1 response in male mice was found to be due to TLR4-derived IL-18, which was originally named IFN--inducing factor, rather than to a classical IL-12/STAT4-induced Th1 response .…”

Testosterone and interleukin-1β increase cardiac remodeling during coxsackievirus B3 myocarditis via serpin A 3n

“…Sections (5 m thick) were stained with hematoxylin and eosin or with Masson's trichrome to detect inflammation or fibrosis, respectively. Myocarditis and fibrosis were assessed as the percentage of the heart section with inflammation or fibrosis compared with the overall size of the heart section using an eyepiece grid at low power (ϫ25), as previously described (9,15,16,19,37). Collagen deposition using Masson's trichrome stains an intensely "baby blue" color compared with inflammation, which appears as dark blue.…”

“…Cardiac function and ventricular dilation were assessed by transthoracic echocardiography (Acuson Sequoia C256, 15-MHz linear transducer, Siemens, Malvern, PA) in conscious mice, as previously described (9,37). The M-mode LV end-systolic crosssectional diameter was determined from an average of three to five cardiac cycles.…”

The 18 kDa Translocator Protein and Atherosclerosis in Mice Lacking Apolipoprotein E

“…According to these models, the inner surface of the channel formed by the TSPO molecule would present a hydrophilic but uncharged pathway, allowing amphiphilic cholesterol molecules to cross the outer mitochondrial membrane (Papadopoulos et al, 1997(Papadopoulos et al, , 2006Veenman et al, 2007). At cellular levels TSPO is present in virtually all of the cells of the cardiovascular system, where they appear to take part in the responses to various challenges that an organism and its cardiovascular system face (Veenman & Gavish, 2006), including atherosclerosis and accompanying symptoms (Onyimba et al, 2011;Bird et al, 2010;Dimitrova-Shumkovska et al, 2010a,b,c, 2012.…”