A molecular mechanism of extracellular vesicle production by alcoholic livers andthe functional impact

Chronic excessive alcohol drinking can lead to serious liver injury. Alcoholic liver disease or alcohol-associated/related liver disease (ALD) is characterized by steatosis, inflammation, and fibrosis, which can lead to cirrhosis, cancer and multiple complications. While significant progress has been made, much has yet to be learnt about the pathogenesis of alcohol-induced liver injury to develop effective therapy and diagnosis. Extracellular vesicles (EVs) are intracellular vesicles released by cells into the extracellular space in response to various physiological and pathological signals. Increased production of EVs in ALD has been found to contribute to the pathogenesis of ALD in a significant way. But the mechanism of enhanced EV production under chronic alcohol exposure is not known. On the other hand, autophagy is an evolutionarily conserved process, and its disturbance can contribute to ALD with the molecular pathway undefined. Interestingly, we find that EVs produced in autophagy deficient mice carry the same molecular signatures as those generated by alcohol-fed mice. Our preliminary findings support a hypothesis that EV production in ALD condition could be driven by a unique regulatory pathway involving autophagy inhibition, activation of NRF2 and upregulation of SDCBP2 and that these molecules can have functional impact on the liver pathologies via the EVs. To examine this hypothesis, we have proposed two specific aims. In Aim 1, we will determine the mechanism of EV production in a mouse model of ALD. Here we will examine how autophagy deficiency following chronic alcohol exposure could promote EVs production. We will examine the molecular link from NRF2 to SDCBP2, both of which are elevated in expression in genetically modified autophagy deficient livers and in chronic alcohol-fed livers. Unlike the steady generation of EVs in basal conditions, this is a regulated pathway to enhance EV production in response to the pathological stimulation of alcohol uptake. In Aim 2, we will determine the contribution of SDCBP2 via enhanced EV production to alcoholic liver pathogenesis. We will examine the effect on inflammation via M1 polarization and other liver pathology. These studies will elucidate an important mechanism that regulate EV production in ALD (a short- term goal), which will significantly advance the field as the identification of new molecular targets could potentially stimulate therapeutic and diagnostic development in future R01-based studies (an intermediate term goal), leading to improved management of ALD (a long-term goal).