Prenatal and Postnatal Mitochondrial Dysfunction in the Pathogenesis of Necrotizing Enterocolitis

The overriding goal of the current proposal is to understand the pathogenesis of neonatal necrotizing enterocolitis (NEC) - the leading cause of death from gastrointestinal disease in premature infants - and to develop novel treatments for this devastating disease. To do so, we will now focus on our recent observation that mitochondrial dysfunction in the intestinal epithelium of the premature infant, followed by bacterial-induced mitochondria damage, are critical for NEC development, and that the reversal of mitochondrial dysfunction can reduce NEC severity. The precise mechanisms by which prematurity and bacterial colonization lead to NEC remain unknown, however, we have previously shown that NEC development requires activation of the bacterial LPS receptor, Toll-like Receptor 4 (TLR4), on the intestinal epithelium of the premature host. We now provide novel preliminary data showing that the intestine of premature mice and human infants is characterized by dysfunctional mitochondria, as manifest by reduced expression of the genes regulating ATP synthesis, and impaired mitochondrial biogenesis, the mechanism by which mitochondria are generated to meet energy demands. TLR4 activation by luminal microbes leads to mitochondrial injury in the premature intestinal epithelium, as revealed by transmission electron microscopy showing vacuolized and damaged mitochondria, a reduction in ATP generation in the intestinal mucosa, reduced mitochondrial membrane potential, release of mitochondrial reactive oxygen species, and damaged mitochondria DNA. TLR4 activation also reduced mitochondrial biogenesis, rendering the premature host unable to meet energy demands. Importantly, mitochondrial dysfunction and impaired mitochondrial biogenesis were required for NEC development, as treatment of mice with mitochondrial protective agents, and the pharmacologic restoration of mitochondrial biogenesis, attenuated NEC severity. These findings led us to develop novel mitochondrial protective agents ("XJB" and "JP4") which restored mitochondrial function in the intestinal mucosa, and attenuated NEC. We now hypothesize that in the intestinal epithelium of the premature host, developmental immaturity of the mitochondria, followed by Joll-[ike Receptor 4 (TLR4)-mediated mitochondria injury in response to dysbiotic microbes, lead to mitochondrial dysfunction, impaired mitochondrial biogenesis and the development of NEC. We further hypothesize that strategies that protect mitochondria in the intestinal epithelium or that enhance mitochondrial biogenesis will serve as novel therapeutic approaches for NEC. We will test these hypotheses in the following specific aims: Aim 1: To investigate how intestinal prematurity and TLR4 activation by luminal microbes lead to mitochondrial dysfunction in the pathogenesis of NEC; Aim 2: To develop novel mitochondrial protective therapies for the prevention or treatment of NEC. If successful, this proposal will offer new clues into the role of mitochondrial dysfunction in the pathogenesis of NEC, and will have developed novel NEC therapies based upon their ability to restore mitochondrial function in the premature, colonized intestine. Project Summary/Abstract