Testing a new strategy to reduce alcohol consumption by pH

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Summary pH is an important biological factor in the nervous system, where it alters the structure and activity of numerous proteins including neurotransmitter receptors, ion channels, and synaptic transmission machinery. It may affect neuronal activities in the circuits responsible for alcohol reward value or alcohol modulatory properties, thereby changing alcohol consumption. This project explores the possibility of reducing alcohol consumption by changing brain pH. We recently reported that knockout mice lacking the pH-regulating transporter NBCn1 fail to maintain normal pH in neurons, causing decreased intracellular pH and decreased cerebrospinal fluid pH. Interestingly, these mice drink more alcohol and develop an increase in the reward value of alcohol. Furthermore, NBCn1 is downregulated in mice chronically fed with alcohol and humans with alcohol use disorder (AUD). Thus, abnormal function in NBCn1 not only influences alcohol consumption, but is also induced by alcohol consumption. The central hypothesis based on our previous and preliminary studies is that alcohol causes NBCn1 downregulation and this downregulation reduces brain pH and subsequently increases alcohol consumption. The goal of the project is to obtain more information on the role of NBCn1-mediated pH regulation in alcohol consumption and to provide a foundation for development of pH-dependent strategies to reduce consumption. Achieving this goal will be important for understanding propensity toward alcoholic ketoacidosis (AKA) and developing a prevention strategy. AKA is a metabolic acidosis induced after binge or chronic alcohol abuse followed by fasting. It is characterized by hyperketonemia and high anion gap metabolic acidosis without significant hyperglycemia, and causes nausea, vomiting, and abdominal pain. Two specific aims are set to achieve the goal. Aim 1 will examine the effects of pH restoration on increased alcohol consumption in NBCn1 knockout mice. The efficacy of pH in reducing alcohol consumption and NBCn1 involvement in this pH effect will be investigated. A mechanistic approach will then be used by injecting NBCn1 to the mouse brain, primarily in the mesolimbic system. Aim 2 will examine the effects of pH on AKA in mice. We developed a mouse model of AKA using a clinically relevant alcohol feeding procedure. We will test whether adjusting systemic pH attenuates AKA and whether NBCn1 is involved. Bicarbonate will be added to the diet and AKA induction and severity will be measured. We will also examine NBCn1 expression and activity during AKA development. In addition, the effects of NBCn1 overexpression in the mesolimbic system will be assessed. The results will provide unprecedented information about the pH effects on alcohol consumption and NBCn1 involvement in producing these effects. We anticipate that the project will lead to the establishment of a new research platform for pH-dependent strategies to reduce alcohol consumption for ordinary drinkers who want to drink less, and chronic or binge drinkers who could be metabolically complicated with AKA.