Inflammatory Disease as Chronic Stress



Abstract: It is now established that communication between the CNS and the immune system is bidirectional, that endocrine factors can alter immune function and that immune responses can alter both endocrine and CNS responses. In many respects CNS and endocrine responses to acute inflammation are similar to the changes associated with acute stress exposure. In contrast, during chronic inflammation associated with adjuvant induced arthritis (AA), although circulating levels of corticosterone are increased, the peptidergic regulation of the hypothalamus is different from that seen during acute stress. As the disease progresses, a paradoxical reduction occurs in CRH mRNA in the paraventricular nucleus (PVN), whereas PVN AVP mRNA increases. These data suggest that there is increased expression of AVP mRNA within the CRH cells of the PVN with an increased emphasis on AVP regulation of HPA output. Additionally, HPA function is altered during chronic inflammation such that responses to psychological stress (i.e. restraint) are significantly dampened, while responses to further inflammatory challenges are maintained. These data suggest that alterations in PVN peptide colocalization may be important in regulating the progression of peripheral inflammatory responses and that the effects of inflammation on the hypothalamus alter stress-responsive systems. In addition to the AA model, we have similarly observed alterations in PVN peptide mRNA expression with disease onset in the murine MRL lpr/lpr and MRL +/+ model of SLE. Disease onset in murine SLE is spontaneous and does not rely on exogenous application of adjuvant; however, decreased levels of CRH in the PVN were observed from early disease onset in this animal model. It is suggested that alterations in CRH regulation in response to either acute or chronic inflammation may contribute as etiological factors to both psychiatric (i.e. neuropsychiatric SLE) and stress-related disease.