Using optogenetics to translate the inflammatory dialogue between heart and brain in the context of stress

Inflammatory processes are an integral part of the stress response and are likely to result from a programmed adaptation that is vital to the organism's survival and well-being. The whole inflammatory response is mediated by largely overlapping circuits in the limbic forebrain, hypothalamus and brainstem, but is also under the control of the neuroendocrine and autonomic nervous systems. Genetically predisposed individuals who fail to tune the respective contributions of the two systems in accordance with stressor modality and intensity after adverse experiences can be at risk for stress-related psychiatric disorders and cardiovascular diseases. Altered glucocorticoid (GC) homeostasis due to GC resistance leads to the failure of neural and negative feedback regulation of the hypothalamic-pituitary-adrenal axis during chronic inflammation, and this might be the mechanism underlying the ensuing brain and heart diseases and the high prevalence of co-morbidity between the two systems. By the combined use of light and genetically-encoded light-sensitive proteins, optogenetics allows cell-type-specific, fast (millisecond-scale) control of precisely defined events in biological systems. This method is an important breakthrough to explore the causality between neural activity patterns and behavioral profiles relevant to anxiety, depression, autism and schizophrenia. Optogenetics also helps to understand the inflammatory dialogue, the inflammatory processes in psychiatric disorders and cardiovascular diseases, shared by heart and brain in the context of stress.