Reduced immune cell infiltration and increased pro-inflammatory mediators in the brain of Type 2 diabetic mouse model infected with West Nile virus

Abstract

BackgroundDiabetes is a significant risk factor for developing West Nile virus (WNV)-associated encephalitis (WNVE) in humans, the leading cause of arboviral encephalitis in the United States. Using a diabetic mouse model (db/db), we recently demonstrated that diabetes enhanced WNV replication and the susceptibility of mice to WNVE. Herein, we have examined immunological events in the brain of wild type (WT) and db/db mice after WNV infection. We hypothesized that WNV-induced migration of protective leukocytes into the brain is attenuated in the presence of diabetes, leading to a high viral load in the brain and severe disease in diabetic mice.MethodsNine-week old C57BL/6 WT and db/db mice were infected with WNV. Leukocyte infiltration, expression of cell adhesion molecules (CAM), neuroinflammatory responses, activation of astrocytes, and neuronal death were analyzed using immunohistochemistry, qRT-PCR, flow cytometry, and western blot.ResultsWe demonstrate that infiltration of CD45+ leukocytes and CD8+T cells was significantly reduced in the brains of db/db mice, which was correlated with attenuated expression of CAM such as E-selectin and ICAM-1. WNV infection in db/db mice was associated with an enhanced inflammatory response in the brain. mRNA and protein levels of key chemokines such as CXCL10, CXCL1, CCL2, CCL5, CCL3, and G-CSF, and cytokines such as IL-1β, TNF, IL-6, IFNγ, and IL-1α were significantly elevated in the brains of db/db mice compared to WT mice. Elevated levels of cytokines also correlated with increased astrocytes activation and neuronal damage in the brains of db/db mice.ConclusionThese data suggest that reduced leukocytes recruitment, in part, due to lower levels of CAM results in failure to clear WNV infection from the brain leading to increased production of inflammatory molecules, which mediates increased neuronal death and mortality in db/db mice. This is the first study to elucidate the expression of CAM and their correlation with the migration of leukocytes, specifically cytotoxic CD8+ T cells, in increasing disease severity in the diabetic mouse model.

Microglia activation due to obesity programs metabolic failure leading to type two diabetes

“…63 The link between glucose intolerance and central inflammation was reported by Kumar M (2014), showing that in the genetic diabetic model (db/db mice) displays increase in mRNA and protein levels of key chemokines such as CXCL10, CXCL1, CCL2, CCL5, CCL3 and G-CSF, and cytokines such as IL-1β, TNF, IL-6, IFNγ and IL-1α compared to WT mice, suggesting that metabolic compromise correlate with central immune response activation despite hypercaloric state. 64 Also, initial research by Velloso's group reported that specific low-grade chronic inflammation modulates body glucose homeostasis, supporting that hypothalamic TNFα administration to rats leads to hyperinsulinemia and insulin resistance in liver and skeletal muscle, 65 and also generates pancreas dysfunction. 66, 67 Of note, these effect are dependent on parasympathetic signals delivered by the vagus nerve to pancreas or liver.…”

Mechanism of West Nile Virus Neuroinvasion: A Critical Appraisal

“…In the case of in vitro WNV infection of endothelium, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and E-selectin appeared to be upregulated (Table 2) [32,45]. The importance of ICAM-1 and E-selectin for leukocytic neuro-infiltration post-WNV inoculation is further supported by in vivo evidence [46,48]. Expression of certain integrins, such as very late antigen (VLA)-4 on LyC6 hi monocyte-derived macrophages, may also be important in aiding migration of particular leukocytes into the CNS in vivo [49].…”

Insulin potentiates JAK/STAT signaling to broadly inhibit flavivirus replication in insect vectors

“…6D-- Prior to our studies, the insulin signaling pathway had not been specifically linked to 305 host immunity to WNV. Intriguingly, however, diabetes mellitus has been shown to 306 increase risk of WNV infection (Nash et al, 2001) and, in mouse models of the disease, 307 leukocyte and T cell recruitment are decreased and WNV replication and 308 neuroinvasiveness are increased in the absence of insulin (Kumar et al, 2012(Kumar et al, , 2014. These 309 observations are mirrored in malaria parasite infection.…”