THE USE OF MRS AND CYTOKINE MEASUREMENTS TO INVESTIGATE DEPRESSION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Investigation of depression has been hampered by the heterogeneity of its causes and presentations. To overcome these impediments, a lesion model of depression would significantly enhance our understanding of this illness. Multiple Sclerosis (MS) has the highest rate of depression of any chronic disease. MS has a 50% prevalence of cognitive impairment. Evidence supports both demyelinated brain lesions and cytokine effects as causes of depression and cognitive dysfunction in MS patients. Transverse Myelitis (TM) is an autoimmune disorder like MS but with demyelinating lesions present only in the spinal cord. We found rates of severe depression in subjects with TM to be higher than those of MS controls and selective cognitive impairments in TM subjects comparable to their MS counterparts. In humans and animals, cytokines induce depression (or its behavioral equivalent) and cognitive impairment. Elevated pro-inflammatory cytokine levels are found in patients with idiopathic depression, which is a state of relative hypercortisolemia. In a homeostatic regulatory cycle, pro-inflammatory cytokines stimulate the HPA axis to release cortisol, which in turn attenuates the immune response. Thus, there is a plausible link in autoimmune disorders between immune system activation with cytokine production and changes in emotional brain states and cognition. We propose that TM provides a model of cytokine-mediated depression and cognitive impairment. We will investigate the epidemiology of these neuropsychiatric phenomena in TM subjects compared to MS and non-autoimmune myelopathy controls including traumatic and non-traumatic spinal cord injury. Our study will then employ neuropsychiatric evaluations, cytokine profiling, and Magnetic Resonance Spectroscopy (MRS) of TM and control subjects to elucidate cytokine elevations and brain neurochemical changes that correlate with depression and cognitive dysfunction. Subjects will be followed longitudinally to determine if changes in cytokine levels and brain metabolites parallel changes in mood, cognition and neurologic outcomes. Neuroendocrine correlates of depression in TM and MS subjects will be ascertained through examination of the function of their HPA axis. We anticipate that the results of this study will have direct implications for the neuropsychiatric comorbidities of TM and MS. These findings could significantly expand our ability to diagnose, prognosticate, and treat neuropsychiatric sequelae in patients with diverse types of autoimmune disorders. These studies also have the potential to illuminate immune mechanisms in idiopathic Major Depression.