Novel Protective Role of Nicotinamide Phosphoribosyltransferase in Acetaminophen-Induced Acute Liver Injury in Mice

Tetramethylpyrazine: A Fermented Alcohol Product that Mitigates Alcoholic Liver Disease in Mice

Alcoholic liver disease (ALD) is a leading cause of premature death globally yet remains under-controlled. In this study, we investigated the protective effects of tetramethylpyrazine (TMP), an aromatic compound found in fermented alcohol, against ALD in a National Institute on Alcohol Abuse and Alcoholism (NIAAA) mice model. Our results demonstrated that TMP significantly reduced alcohol-induced liver injury, steatosis, oxidative stress, and mitochondrial damage, while restoring NAD+ levels and the NAD+/NADH ratio, increasing ATP production, regulating energy metabolism disorders, and restoring metabolic balance (P < 0.05). Liver transcriptomic analysis identified 906 ALD-associated genes enriched in energy and lipid metabolism pathways, with a molecular signature of NAD-dependent oxidoreductase activity. Protein interaction analysis predicted Nicotinamide Phosphoribosyltransferase (NAMPT) as a key rate-limiting enzyme in NAD metabolism. Cellular Thermal Shift Assay (CETSA) experiments and molecular docking studies further confirmed that TMP can restore the level of NAD+ by stabilizing the NAMPT protein. TMP is present in various foods, including Semen Sojae Preparatum, a TMP-rich fermented food commonly used in Traditional Chinese Medicine for ALD treatment. This food exhibited significant protective effects against ALD. In conclusion, TMP, an aromatic compound in fermented alcohol, could protect the liver from alcohol-induced damage. Enhancing TMP content in fermented alcohol holds significant promise for mitigating the adverse effects of alcohol consumption on the liver.

Deciphering Acetaminophen-Induced Hepatotoxicity: The Crucial Role of Transcription Factors like Nuclear Factor Erythroid 2-Related Factor 2 as Genetic Determinants of Susceptibility to Drug-Induced Liver Injury

Acetaminophen (APAP) is the most commonly used over-the-counter medication throughout the world. At therapeutic doses, APAP has potent analgesic and antipyretic effects. The efficacy and safety of APAP are influenced by multifactorial processes dependent upon dosing, namely frequency and total dose. APAP poisoning by repeated ingestion of supratherapeutic doses, depletes glutathione stores in the liver and other organs capable of metabolic bioactivation, leading to hepatocellular death due to exhausted antioxidant defenses. Numerous genes, encompassing transcription factors and signaling pathways, have been identified as playing pivotal roles in APAP toxicity, with the liver being the primary organ studied due to its central role in APAP metabolism and injury. Nuclear factor erythroid 2-related factor 2 (NRF2) and its array of downstream responsive genes are crucial in counteracting APAP toxicity. NRF2, along with its negative regulator Kelch-like ECH-associated protein 1, plays a vital role in regulating intracellular redox homeostasis. This regulation is significant in modulating the oxidative stress, inflammation, and hepatocellular death induced by APAP. In this review, we provide an updated overview of the mechanisms through which NRF2 activation and signaling critically influence the threshold for developing APAP toxicity. We also describe how genetically modified rodent models for NRF2 and related genes have been pivotal in underscoring the significance of this antioxidant response pathway. While NRF2 is a primary focus, the article comprehensively explores other genetic factors involved in phase I and phase II metabolism of APAP, inflammation, oxidative stress, and related pathways that contribute to APAP toxicity, thereby providing a holistic understanding of the genetic landscape influencing susceptibility to this condition. SIGNIFICANCE STATEMENT: This review summarizes the genetic elements and signaling pathways underlying APAP-induced liver toxicity, focusing on the crucial protective role of the transcription factor NRF2. This review also delves into the genetic intricacies influencing APAP safety and potential liver harm. It also emphasizes the need for deeper insight into the molecular mechanisms of hepatotoxicity, especially the interplay of NRF2 with other pathways.

P7C3 Ameliorates Bone Loss by Inhibiting Osteoclast Differentiation and Promoting Osteogenesis

Bone homeostasis, the equilibrium between bone resorption and formation, is essential for maintaining healthy bone tissue in adult humans. Disruptions of this process can lead to pathological conditions such as osteoporosis. Dual-targeted agents, capable of inhibiting excessive bone resorption and stimulating bone formation, are being explored as a promising strategy for developing new treatments to address osteoporosis. In this study, we investigated the effects of P7C3 on bone remodeling and its potential therapeutic role in osteoporosis treatment in mice. Specifically, P7C3 can remarkably suppress receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation in bone marrow macrophages via the Akt-NF-κB-NFATc1 signaling pathway. Additionally, RNA sequencing (RNAseq) analysis revealed that P7C3 promoted osteoblast differentiation and function through the Wnt/β-catenin signaling pathway, thereby enhancing bone formation. Furthermore, μCT analysis and histological examination of bone tissues from P7C3-treated mice showed attenuation of both Ti-induced bone erosion and ovariectomy (OVX)-induced bone loss. These findings suggest that P7C3 may have a novel function in bone remodeling and may be a promising therapeutic agent for the treatment of osteoporosis. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Application of P7C3 Compounds to Investigating and Treating Acute and Chronic Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading worldwide cause of disability, and there are currently no medicines that prevent, reduce, or reverse acute or chronic neurodegeneration in TBI patients. Here, we review the target-agnostic discovery of nicotinamide adenine dinucleotide (NAD+)/NADH-stabilizing P7C3 compounds through a phenotypic screen in mice and describe how P7C3 compounds have been applied to advance understanding of the pathophysiology and potential treatment of TBI. We summarize how P7C3 compounds have been shown across multiple laboratories to mitigate disease progression safely and effectively in a broad range of preclinical models of disease related to impaired NAD+/NADH metabolism, including acute and chronic TBI, and note the reported safety and neuroprotective efficacy of P7C3 compounds in nonhuman primates. We also describe how P7C3 compounds facilitated the recent first demonstration that chronic neurodegeneration 1 year after TBI in mice, the equivalent of many decades in people, can be reversed to restore normal neuropsychiatric function. We additionally review how P7C3 compounds have facilitated discovery of new pathophysiologic mechanisms of neurodegeneration after TBI. This includes the role of rapid TBI-induced tau acetylation that drives axonal degeneration, and the discovery of brain-derived acetylated tau as the first blood-based biomarker of neurodegeneration after TBI that directly correlates with the abundance of a therapeutic target in the brain. We additionally review the identification of TBI-induced tau acetylation as a potential mechanistic link between TBI and increased risk of Alzheimer's disease. Lastly, we summarize historical accounts of other successful phenotypic-based drug discoveries that advanced medical care without prior recognition of the specific molecular target needed to achieve the desired therapeutic effect.

Hepatic Nampt Deficiency Aggravates Dyslipidemia and Fatty Liver in High Fat Diet Fed Mice

Nicotinamide phosphoribosyltransferase (Nampt) is the rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide (NAD) biosynthesis. Thus far, hepatic Nampt has not been extensively explored in terms of its effects on serum lipid stability and liver lipids metabolism. In this study, hepatocyte-specific Nampt knockout (HC-Nampt^-/-) mice were generated by Cre/loxP system. Nampt mRNA expression was reduced in the liver, but not in other tissues, in HC-Nampt^-/- mice compared with wild-type (WT) mice. Hepatic Nampt deficiency had no effect on body weight and fasting blood glucose, and it did not induce atherosclerosis in mice under both normal chow diet (NCD) and high fat diet (HFD). At baseline state under NCD, hepatic Nampt deficiency also did not affect liver weight, liver function index, including alanine aminotransferase, aspartate aminotransferase, albumin and alkaline phosphatase, and serum levels of lipids, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and non-esterified fatty acids (NEFA). However, under HFD, deficiency of hepatic Nampt resulted in increased liver weight, liver function index, and serum levels of TG, TC, HDL-C, and NEFA. Meanwhile, histopathological examination showed increased fat accumulation and fibrosis in the liver of HC-Nampt^-/- mice compared with WT mice. Taken together, our results show that hepatic Nampt deficiency aggravates dyslipidemia and liver damage in HFD fed mice. Hepatocyte Nampt can be a protective target against dyslipidemia and fatty liver.

Identification of Genes Regulating Hepatocyte Injury by a Genome-Wide CRISPR-Cas9 Screen

Gene editing introduces stable mutations into the genome and has powerful applications extending from research to clinical gene therapy. CRISPR-Cas9 gene editing can be employed to study directly the functional impact of stable gene knockout, activation, and knockdown. Here, we describe the end-to-end methodology by which we employ genome-wide CRISPR-Cas9 knockout to study drug toxicity using acetaminophen (APAP) in a hepatocellular carcinoma liver model as an example. This methodology can be extended to other proliferative cell types and chemical metabolic and toxicity models. By employing a massively parallelized genome-wide knockout model, the genes responsible for cellular toxicity and proliferation may be assayed concurrently. Resultant data are interrogated in the context of existing gene expression data, pathway analysis, drug-gene interactions, and orthogonal confirmatory assays to better understand the metabolic mechanisms.

Nicotinamide improves NAD+ levels to protect against acetaminophen-induced acute liver injury in mice

Acetaminophen (APAP) overdose causes acute liver injury (ALI). Nicotinamide adenine dinucleotide (NAD) is an essential coenzyme, and NAD⁺ is oxidized type which synthesized from nicotinamide (NAM). The present study aimed to investigate the role of NAD⁺ in ALI and protective property of NAM. The mice were subjected to different doses APAP. After 8 hours, the serum activities of alaninetransaminase (ALT) and aspartate aminotransferase (AST), the hepatic NAD⁺ level and nicotinamide phosphoribosyltransferase (NAMPT) expression were determined. Then, the mice were pretreated with NAM (800 mg/kg), the hepatoprotective effects and the key antioxidative molecules were evaluated. Our findings indicated that APAP resulted in remarkable NAD⁺ depletion in a dose-dependent manner accompanied by NAMPT downregulation, and NAM pretreatment significantly elevated the NAD⁺ decline due to upregulation of NAMPT. Moreover, the downregulated Kelch-like ECH-associated protein-1 (Keap1), upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and its translocation activation after NAM administration were confirmed, which were in accordance with improved superoxide dismutase (SOD) and glutathione (GSH) levels. Finally, NAM dramatically exhibited hepatoprotective effects by reducing the liver index and necrotic area. This study has suggested that APAP impairs liver NAD⁺ level and NAM is able to improve hepatic NAD⁺ to activate antioxidant pathway against APAP-induced ALI.

The Critical Role of SIRT1 in Parkinson's Disease: Mechanism and Therapeutic Considerations

Silence information regulator 1 (SIRT1), a member of the sirtuin family, targets histones and many non-histone proteins and participates in various physiological functions. The enzymatic activity of SIRT1 is decreased in patients with Parkinson’s disease (PD), which may reduce their ability to resist neuronal damage caused by various neurotoxins. As far as we know, SIRT1 can induce autophagy by regulating autophagy related proteins such as AMP-activated protein kinase, light chain 3, mammalian target of rapamycin, and forkhead transcription factor 1. Furthermore, SIRT1 can regulate mitochondrial function and inhibit oxidative stress mainly by maintaining peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in a deacetylated state and thus maintaining a constant level of PGC-1α. Other studies have demonstrated that SIRT1 may play a role in the pathophysiology of PD by regulating neuroinflammation. SIRT1 deacetylases nuclear factor-kappa B and thus reduces its transcriptional activity, inhibits inducible nitric oxide synthase expression, and decreases tumor necrosis factor-alpha and interleukin-6 levels. SIRT1 can also upregulate heat shock protein 70 by deacetylating heat shock factor 1 to increase the degradation of α-synuclein oligomers. Few studies have focused on the relationship between SIRT1 single nucleotide polymorphisms and PD risk, so this topic requires further research. Based on the neuroprotective effects of SIRT1 on PD, many in vitro and in vivo experiments have demonstrated that some SIRT1 activators, notably resveratrol, have potential neuroprotective effects against dopaminergic neuronal damage caused by various neurotoxins. Thus, SIRT1 plays a critical role in PD development and might be a potential target for PD therapy.

Epigenetic regulation of NfatC1 transcription and osteoclastogenesis by nicotinamide phosphoribosyl transferase in the pathogenesis of arthritis

Nicotinamide phosphoribosyltransferase (NAMPT) functions in NAD synthesis, apoptosis, and inflammation. Dysregulation of NAMPT has been associated with several inflammatory diseases, including rheumatoid arthritis (RA). The purpose of this study was to investigate NAMPT’s role in arthritis using mouse and cellular models. Collagen-induced arthritis (CIA) in DBA/1J Nampt^+/− mice was evaluated by ELISA, micro-CT, and RNA-sequencing (RNA-seq). In vitro Nampt loss-of-function and gain-of-function studies on osteoclastogenesis were examined by TRAP staining, nascent RNA capture, luciferase reporter assays, and ChIP-PCR. Nampt-deficient mice presented with suppressed inflammatory bone destruction and disease progression in a CIA mouse model. Nampt expression was required for the epigenetic regulation of the Nfatc1 promoter and osteoclastogenesis. Finally, RNA-seq identified 690 differentially expressed genes in whole ankle joints which associated (P < 0.05) with Nampt expression and CIA. Selected target was validated by RT-PCR or functional characterization. We have provided evidence that NAMPT functions as a genetic risk factor and a potential therapeutic target to RA.

Identification of Novel Regulatory Genes in APAP Induced Hepatocyte Toxicity by a Genome-Wide CRISPR-Cas9 Screen

Acetaminophen (APAP) is a commonly used analgesic responsible for more than half of acute liver failure cases. Identification of previously unknown genetic risk factors would provide mechanistic insights and novel therapeutic targets for APAP-induced liver injury. This study used a genome-wide CRISPR-Cas9 screen to evaluate genes that are protective against, or cause susceptibility to, APAP-induced liver injury. HuH7 human hepatocellular carcinoma cells containing CRISPR-Cas9 gene knockouts were treated with 15 mM APAP for 30 minutes to 4 days. A gene expression profile was developed based on the 1) top screening hits, 2) overlap of expression data from APAP overdose studies, and 3) predicted affected biological pathways. We further demonstrated the implementation of intermediate time points for the identification of early and late response genes. This study illustrated the power of a genome-wide CRISPR-Cas9 screen to systematically identify novel genes involved in APAP-induced hepatotoxicity and to provide potential targets to develop novel therapeutic modalities.

Neuroprotective efficacy of P7C3 compounds in primate hippocampus

There is a critical need for translating basic science discoveries into new therapeutics for patients suffering from difficult to treat neuropsychiatric and neurodegenerative conditions. Previously, a target-agnostic in vivo screen in mice identified P7C3 aminopropyl carbazole as capable of enhancing the net magnitude of postnatal neurogenesis by protecting young neurons from death. Subsequently, neuroprotective efficacy of P7C3 compounds in a broad spectrum of preclinical rodent models has also been observed. An important next step in translating this work to patients is to determine whether P7C3 compounds exhibit similar efficacy in primates. Adult male rhesus monkeys received daily oral P7C3-A20 or vehicle for 38 weeks. During weeks 2-11, monkeys received weekly injection of 5'-bromo-2-deoxyuridine (BrdU) to label newborn cells, the majority of which would normally die over the following 27 weeks. BrdU+ cells were quantified using unbiased stereology. Separately in mice, the proneurogenic efficacy of P7C3-A20 was compared to that of NSI-189, a proneurogenic drug currently in clinical trials for patients with major depression. Orally-administered P7C3-A20 provided sustained plasma exposure, was well-tolerated, and elevated the survival of hippocampal BrdU+ cells in nonhuman primates without adverse central or peripheral tissue effects. In mice, NSI-189 was shown to be pro-proliferative, and P7C3-A20 elevated the net magnitude of hippocampal neurogenesis to a greater degree than NSI-189 through its distinct mechanism of promoting neuronal survival. This pilot study provides evidence that P7C3-A20 safely protects neurons in nonhuman primates, suggesting that the neuroprotective efficacy of P7C3 compounds is likely to translate to humans as well.