Hemantkumar Chavan

University of Kansas | KU · Department of Pharmacology, Toxicology and Therapeutics

Duloxetine (DLX) is a dual serotonin and norepinephrine reuptake inhibitor, widely used for the treatment of major depressive disorder. Although DLX has shown good efficacy and safety, serious adverse effects (e.g., liver injury) have been reported. The mechanisms associated with DLX-induced toxicity remain elusive. Drug metabolism plays critical r...

Mitochondria damage plays a critical role in acetaminophen (APAP)-induced necrosis and liver injury. Cells can adapt and protect themselves by removing damaged mitochondria via mitophagy. PINK1-Parkin pathway is one of the major pathways that regulate mitophagy but its role in APAP-induced liver injury is still elusive. We investigated the role of...

Early mammalian development is critically dependent on the establishment of oxidative energy metabolism within the trophectoderm (TE) lineage. Unlike inner cell mass (ICM), TE cells enhance ATP production via mitochondrial oxidative phosphorylation (OXPHOS) and this metabolic preference is essential for blastocyst maturation. However, molecular mec...

Despite aggressive therapies, head and neck squamous cell carcinoma (HNSCC) is associated with a less than 50% 5-year survival rate. Late-stage HNSCC frequently consists of up to 80% cancer-associated fibroblasts (CAF). We previously reported that CAF-secreted HGF facilitates HNSCC progression; however, very little is known about the role of CAFs i...

Background & aims: Defects in lysosome function and autophagy contribute to pathogenesis of alcoholic liver disease. We investigated the mechanisms by which alcohol consumption affects these processes, evaluating the functions transcription factor EB (TFEB), which regulates lysosomal biogenesis. Methods: We performed studies with GFP-LC3 mice, m...

Head and neck squamous cell carcinoma (HNSCC) affects 40,000 patients annually and is associated with <50% 5-year survival. There is an urgent need to better understand the biology of the disease in order to develop more effective therapeutic approaches. HNSCC tumors are dysplastic with up to 80% fibroblasts. We recently reported that tumor-associa...

Epidermal growth factor receptor (EGFR) plays a crucial role in hepatocyte proliferation. Its role in acetaminophen (APAP)- mediated hepatotoxicity and subsequent liver regeneration is completely unknown. Role of EGFR after APAP-overdose in mice was studied using pharmacological inhibition strategy. Rapid, sustained and dose-dependent activation of...

Arsenite is a known carcinogen and its exposure has been implicated in a variety of noncarcinogenic health concerns. Increased oxidative stress is thought to be the primary cause of arsenite toxicity and the toxic effect is thought to be linear with detrimental effects reported at all concentrations of arsenite. But the paradigm of linear dose resp...

Arsenic exposure did not affect cellular ATP levels significantly. suggesting that the increased oxygen consumption in response to low dose arsenite exposure was not a result of increased coupling efficiency. Interestingly, when oligomycin was added to inhibit oxidative phosphorylation to measure coupling efficneicny, primary hepatocytes demonstrat...

Liver plays a key role in cholesterol metabolism. Impaired hepatic cholesterol homeostasis causes intracellular free cholesterol accumulation and hepatocyte injury. Sortilin 1 (Sort1) is an intracellular lysosomal trafficking receptor that was recently identified by GWAS as a novel regulator of cholesterol metabolism in humans. Here we report that...

Background & Aims Hepatic cholesterol accumulation and autophagy defects contribute to hepatocyte injury in fatty liver disease. Bile acid synthesis is a major pathway for cholesterol catabolism in the liver. This study aims to understand the molecular link between cholesterol and bile acid metabolism and hepatic autophagy activity. Methods The ef...

Overdose of acetaminophen (APAP) causes severe liver injury and even acute liver failure in both mice and human. A recent study by Kim et al. (2015) showed that metformin, a first-line drug to treat type 2 diabetes mellitus, protected against APAP hepatotoxicity in mice. However, its exact protective mechanism has not been well clarified. To invest...

Despite aggressive therapies, head and neck squamous cell carcinoma (HNSCC), which affects 50,000 new patients annually in the United States, is associated with less than 50% 5-year survival. HNSCC tumors display increased glycolysis, even in the presence of oxygen. Consequently, there is an increase in lactic acid (LA) production. However, the eff...

Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy affecting 40,000 cases in the USA annually. Despite aggressive therapies HNSCC is associated with less than a 50% 5-year survival rate. Limited treatment options and high morbidity necessitate the development of new treatments. HNSCC tumors frequently consist of up to 80% tum...

Although endogenous mechanisms that negatively regulate Cytochrome P450 (P450) monooxygenases in response to physiological and pathophysiological signals are not well understood it is thought to result from alterations in the level of endogenous metabolites involved in maintaining homeostasis. Here we show that homeostatic changes in hepatic metabo...

The mitochondrial ATP binding cassette transporter ABCB6 has been associated with a broad range of physiological functions, including growth and development, therapy-related drug resistance, and the new blood group system Langereis. ABCB6 has been proposed to regulate heme synthesis by shuttling coproporphyrinogen III from the cytoplasm into the mi...

ABCB6 is a member of the adenosine triphosphate (ATP)-binding cassette family of transporter proteins that is increasingly recognized as a relevant physiological and therapeutic target. Evaluation of modulators of ABCB6 activity would pave the way toward a more complete understanding of the significance of this transport process in tumor cell growt...

ABCB6 high-throughput screening assay flow-chart. (TIF)

Viability of K562 cells exposed to DMSO. DMSO at a concentration of 1% does not affect K562 cell survival following 24 hr exposure. (TIF)

Schematic representation of ABCB6 hemin-agarose affinity chromatography. (TIF)

Flow cytometric HTS of Prestwick Chemical Library (PCL). The figure depicts data from a representative PCL plate demonstrating decrease in FL2 fluorescence (representing PPIX fluorescence) mediated by (a) benzethonium chloride, (b) piperlongumine, and (c) tomatine hydrochloride (tomatine). Figure (c) also demonstrates three potential activators of...

Chemical structures of the identified lead compounds, benzethonium chloride (BCL), verteporfin (VRP) tomatine hydrochloride (THC) and piperlongumine (PLG). (TIF)

SDS-PAGE analysis of purified ABCB6 and selectivity and validation of HTS identified compounds by hemin-agarose affinity chromatography using purified ABCB6. (a) Purified ABCB6 sample was analyzed by SDS-PAAGE. The figure shows silver staining of SDS gel (lane legends are 1, protein marker; 2, purified ABCB6-flag 3 µg protein). b) verteporfin and (...

Selectivity and validation of HTS identified compounds by hemin-agarose affinity chromatography using purified ABCB6. a) verteporfin and (b) tomatine hydrochloride potently disrupt the interaction between purified ABCB6 protein and hemin-agarose. Three hundred nanograms of purified ABCB6-flag protein was incubated in the presence or absence of incr...

Human erythroleukemia cells (K562) expressing ABCB6 have stable expression of ABCB6. The data show comparable ABCB6 expression in ABCB6 overexpressing cells that have undergone either 2 or 60 passages, indicating that ABCB6 expression in overexpressing cells is stable for upto 60 passages. Porin is used as the mitochondrial loading control. Figure...

The sequence of the human ABCB6 transporter (UniProt accesion code: Q9NP58) aligned with both the Val33-Thr626 and Leu684-Ala1271 parts of the sequence of the mouse ABCB1a (PDB code: 3G5U). (TIF)

Liver is endowed with a mechanism to induce hepatic cytochromes P450 (CYP450s) in response to therapeutic drugs and environmental contaminants, leading to increased detoxification and elimination of the xenobiotics. Each CYP450 is composed of an apoprotein moiety and a heme prosthetic group, which is required for CYP450 activity. Thus, under condit...

ABCB6 is a mitochondrial ATP binding cassette (ABC) transporter whose expression is upregulated in a broad spectrum of primary human cancers, including hepatocellular carcinoma (HCC). We recently demonstrated that in hepatoma cells ABCB6 expression promotes growth and proliferation. In contrast, loss of ABCB6 expression in these hepatomas precipita...

ABCB6 is a mitochondrial transporter that regulates porphyrin biosynthesis. ABCB6 expression is upregulated in hepatocellular carcinoma (HCC) but the significance of this upregulation to HCC is not known. In the present study, we investigated: 1) ABCB6 expression in 18 resected human hepatocellular carcinoma (HCC) tissues and 3 human hepatoma cell...

Arsenic, an environmental carcinogen, remains a major public health problem. Arsenic damages biological systems through multiple mechanisms, including the generation of reactive oxygen species. ABCB6 is an ATP-binding cassette transporter that is highly expressed in cells resistant to arsenic. We have recently demonstrated that ABCB6 expression pro...

Leishmania donovani, causative organism for visceral leishmaniasis, is responsible for considerable mortality and morbidity worldwide. Generation of drug-resistant variants continue to challenge the chemotherapy, the mainstay to fight the disease. The aim of current study was proteomic profiling of wild type (Ld-Wt) and arsenite-resistant (Ld-As20)...

The affinity of arsenic towards the cytoskeleton leading to disturbance of tubulin polymerization is well known. Tubulin undergoes extensive posttranslational modifications which effect stability and dynamics of microtubules but little is known about the effect of antimicrotubule drugs on their distribution and function in kinetoplastid parasites s...