Phosphodiesterase 4B Inhibition as a Therapeutic Target for Alcohol-associated Liver Disease

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PROJECT SUMMARY Alcohol-associated liver disease (ALD) is a significant health problem caused by excessive alcohol consumption. ALD is generally discovered in association with fatty liver, steatosis, or fibrosis progression, leading to cirrhosis. Unfortunately, there is no approved drug for ALD, and the current therapies rely on abstinence, immune suppressants like corticosteroids, or liver transplantation in case of advanced cirrhosis. Studies suggest that inflammation plays a significant role in ALD initiation and progression. Kupffer cells (KCs), the residing macrophages in the liver, are mainly involved in hepatic inflammatory reactions. KCs, upon contact with injured hepatocytes or gut bacterial endotoxins such as lipopolysaccharides (LPS), get activated and secrete inflammatory cytokines, including TNF-α and start the inflammation. Pharmacological inhibition of KCs by small molecules such as gadolinium chloride or decreasing intestinal bacterial load with antibiotics is shown to prevent liver injury and ALD progression. Cyclic adenosine monophosphate (cAMP) signaling plays a significant role in dampening hepatic injury and steatosis. Alcohol is known to increase the expression of cAMP degrading enzyme phosphodiesterase 4 (PDE4). The upregulated PDE4 decreases the cAMP levels and induces liver inflammation/injury. PDE4 inhibitors have been investigated to inhibit macrophage recruitment and activation in ALD; however, the current PDE4 inhibitors such as rolipram and roflumilast are associated with severe side effects, including nausea, vomiting, diarrhea, and dyspepsia. This study aims to inhibit PDE4B activity by novel inhibitor KVA-D-88 in alcohol-induced steatosis. Our preliminary data show that KVA-D-88 is a potent and selective PDE4B inhibitor with a suitable pharmacokinetic profile. The development of highly selective PDE4B inhibitors such as KVA-D-88 directly applies to human ALD. However, PDE4B inhibition in other organs, such as the brain, is known to produce severe side effects. Therefore, there is a need for KC-specific drug delivery to enhance the drug efficacy and specificity. We will develop KVA-D-88 nanoparticles for liver-specific PDE4B inhibition. Our specific aims are Aim 1 to establish the role of PDE4B inhibitor KVA-D-88 in ALD in vitro and in vivo. In this aim, we will determine the specificity of KVA-D-88 to inhibit PDE4B isotype compared to PDE4D isotype in alcohol-induced primary KCs, hepatocytes, and hepatic stellate cells (HSCs). Next, we will evaluate the effect of KVA-D-88 mediated PDE4B inhibition on cAMP signaling, TNF-α induced ER stress, and ethanol- induced toxicity in the modified NIAAA mouse model. Aim 2. Formulate and characterize KCs targeted KVA- D-88 loaded polyethylene glycol (PEG) decorated solid lipid nanoparticles (SLNs). In this aim, we will develop and characterize KCs targeted PEG-SLNs loaded with KVA-D-88. Next, we will evaluate the therapeutic efficacy of KVA-D-88 loaded SLNs in the NIAAA model. This project is highly significant as it could provide us with ALD therapy and a potential platform for nonalcoholic fatty liver disease (NAFLD) and cholestasis-induced liver fibrosis.