Potent and multiple regulatory actions of microglial glucocorticoid receptors during CNS inflammation

In CNS, glucocorticoids (GCs) activate both GC receptor (GR) and mineralocorticoid receptor (MR), whereas GR is widely expressed, the expression of MR is restricted. However, both are present in the microglia, the resident macrophages of the brain and their activation can lead to pro- or anti-inflammatory effects. We have therefore addressed the specific functions of GR in microglia. In mice lacking GR in macrophages/microglia and in the absence of modifications in MR expression, intraparenchymal injection of lipopolysaccharide (LPS) activating Toll-like receptor 4 signaling pathway resulted in exacerbated cellular lesion, neuronal and axonal damage. Global inhibition of GR by RU486 pre-treatment revealed that microglial GR is the principal mediator preventing neuronal degeneration triggered by lipopolysaccharide (LPS) and contributes with GRs of other cell types to the protection of non-neuronal cells. In vivo and in vitro data show GR functions in microglial differentiation, proliferation and motility. Interestingly, microglial GR also abolishes the LPS-induced delayed outward rectifier currents by downregulating Kv1.3 expression known to control microglia proliferation and oxygen radical production. Analysis of GR transcriptional function revealed its powerful negative control of pro-inflammatory effectors as well as upstream inflammatory activators. Finally, we analyzed the role of GR in chronic unpredictable mild stress and aging, both known to prime or sensitize microglia in vivo. We found that microglial GR suppresses rather than mediates the deleterious effects of stress or aging on neuronal survival. Overall, the results show that microglial GR acts on several key processes limiting pro-inflammatory actions of activated microglia

Can behavioral theory inform the understanding of depression and medication nonadherence among HIV-positive substance users?

Medication adherence is highly predictive of health outcomes across chronic conditions, particularly HIV/AIDS. Depression is consistently associated with worse adherence, yet few studies have sought to understand how depression relates to adherence. This study tested three components of behavioral depression theory—goal-directed activation, positive reinforcement, and environmental punishment—as potential indirect effects in the relation between depressive symptoms and medication nonadherence among low-income, predominantly African American substance users (n = 83). Medication nonadherence was assessed as frequency of doses missed across common reasons for nonadherence. Non-parametric bootstrapping was used to evaluate the indirect effects. Of the three intermediary variables, there was only an indirect effect of environmental punishment; depressive symptoms were associated with greater nonadherence through greater environmental punishment. Goal-directed activation and positive reinforcement were unrelated to adherence. Findings suggest the importance of environmental punishment in the relation between depression and medication adherence and may inform future intervention efforts for this population