This grant application proposes a 5 year training program to launch the academic career of an independent cardiovascular physiologist and academic anesthesiologist. The Principal Investigator is a Board Certified Anesthesiologist at Massachusetts General Hospital in Boston, with a PhD and prior postdoctoral experience in cardiac physiology. The broad, overarching goal of the PI's research efforts is to elucidate cellular mechanisms that cause cardiac dysfunction in a variety of disease states, and to discover novel therapeutic strategies. Within this broad goal, the current Application proposes to identify the specific calcium (Ca2+) regulating proteins and signaling pathways that underlie cardiac dysfunction in sepsis and septic shock. More specifically, this Application challenges the current view that sepsis-induced cardiomyopathy (SIC) is mediated by an increase in cardiac cGMP levels caused by activation of the enzyme soluble guanylyl cyclase (sGC) by nitric oxide (NO). Contrary to the current paradigm, provocative recent studies revealed that, in mice, the absence of the sGC enzyme was associated with a worsening of septic shock and cardiomyopathy. This argues against a primary deleterious effect of sGC and cGMP, and suggests, instead, that the deleterious effects of NO may be mediated through non-cGMP-dependent effects, and in particular, oxidative modification of Ca2+ regulatory proteins. The proposed experiments will study a mouse model of SIC, and will identify the specific Ca2+ regulatory proteins involved as well as the specific oxidative changes of these proteins (Specific Aim I). Subsequent studies propose to reproduce the dysfunction of cellular Ca2+ transporters induced by sepsis in vitro (Specific Aim II), and to correct this dysfunction by increasing cellular antioxidant defenses (Specific Aim III). Finally, Specific Aim IV hypothesizes that sGC may actually play a cardioprotective role in sepsis and proposes to identify the underlying mechanisms. The proposed experiments will take place in the Myocardial Biology Unit at Boston University Medical Center Campus, under the Mentorship of two prominent cardiovascular biologists, Drs. Wilson S. Colucci (the primary Mentor) and Richard A. Cohen (the Co-Mentor), with proven leadership in the field of oxidative signaling. The project will provide the PI with an ambitious training program in biochemical and molecular biology techniques, supervised by a select committee of recognized experts.