Seong-Kyu Choe

Capsaicin Ameliorates Cisplatin-Induced Renal Injury through Induction of Heme Oxygenase-1

Cisplatin is one of the most potent chemotherapy agents. However, its use is limited due to its toxicity in normal tissues, including the kidney and ear. In particular, nephrotoxicity induced by cisplatin is closely associated with oxidative stress and inflammation. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in the heme metabolism, has been implicated in a various cellular processes, such as inflammatory injury and anti-oxidant/oxidant homeostasis. Capsaicin is reported to have therapeutic potential in cisplatin-induced renal failures. However, the mechanisms underlying its protective effects on cisplatin-induced nephrotoxicity remain largely unknown. Herein, we demonstrated that administration of capsaicin ameliorates cisplatin-induced renal dysfunction by assessing the levels of serum creatinine and blood urea nitrogen (BUN) as well as tissue histology. In addition, capsaicin treatment attenuates the expression of inflammatory mediators and oxidative stress markers for renal damage. We also found that capsaicin induces HO-1 expression in kidney tissues and HK-2 cells. Notably, the protective effects of capsaicin were completely abrogated by treatment with either the HO inhibitor ZnPP IX or HO-1 knockdown in HK-2 cells. These results suggest that capsaicin has protective effects against cisplatin-induced renal dysfunction through induction of HO-1 as well as inhibition oxidative stress and inflammation.

Bucillamine prevents cisplatin-induced ototoxicity through induction of glutathione and antioxidant genes

Bucillamine is used for the treatment of rheumatoid arthritis. This study investigated the protective effects of bucillamine against cisplatin-induced damage in auditory cells, the organ of Corti from postnatal rats (P2) and adult Balb/C mice. Cisplatin increases the catalytic activity of caspase-3 and caspase-8 proteases and the production of free radicals, which were significantly suppressed by pretreatment with bucillamine. Bucillamine induces the intranuclear translocation of Nrf2 and thereby increases the expression of γ-glutamylcysteine synthetase (γ-GCS) and glutathione synthetase (GSS), which further induces intracellular antioxidant glutathione (GSH), heme oxygenase 1 (HO-1) and superoxide dismutase 2 (SOD2). However, knockdown studies of HO-1 and SOD2 suggest that the protective effect of bucillamine against cisplatin is independent of the enzymatic activity of HO-1 and SOD. Furthermore, pretreatment with bucillamine protects sensory hair cells on organ of Corti explants from cisplatin-induced cytotoxicity concomitantly with inhibition of caspase-3 activation. The auditory-brainstem-evoked response of cisplatin-injected mice shows marked increases in hearing threshold shifts, which was markedly suppressed by pretreatment with bucillamine in vivo. Taken together, bucillamine protects sensory hair cells from cisplatin through a scavenging effect on itself, as well as the induction of intracellular GSH.

Activation of β-catenin by inhibitors of glycogen synthase kinase-3 ameliorates cisplatin-induced cytotoxicity and pro-inflammatory cytokine expression in HEI-OC1 cells.

Cisplatin is used in the treatment of a wide variety of solid tumors, but its use is limited by its serious adverse effects, including ototoxicity. Glycogen synthase kinase-3 (GSK-3) is a ubiquitously expressed serine/threonine kinase that regulates a variety of cellular functions by phosphorylating its substrates. However, the otoprotective effect of GSK-3 inhibitors is poorly understood. Here, we investigated whether GSK-3 is involved in cisplatin-induced ototoxicity in HEI-OC1 cells and organs of Corti (OCs). GSK-3 inhibitors suppressed cisplatin-induced apoptosis determined by decreased p53 activity, and also decreased expression of PARP and p53 target genes such as p21 and PUMA. The effect of GSK-3 inhibitors was mediated by markedly increased nuclear β-catenin that in turn blocked nuclear translocation of NF-κB. siRNA-mediated β-catenin knockdown markedly increased the expression of NF-κB target genes, such as TNF-α and IL-6. Our data suggest that the GSK-3/β-catenin pathway may play a central role in cisplatin-mediated cytotoxicity in HEI-OC1 cells and hair cells of OCs in vitro.

Establishment of a bone-specific col10a1:GFP transgenic zebrafish

During skeletal development, both osteogenic and chondrogenic programs are initiated from multipotent mesenchymal cells, requiring a number of signaling molecules, transcription factors, and downstream effectors to orchestrate the sophisticated process. Col10a1, an important downstream effector gene, has been identified as a marker for maturing chondrocytes in higher vertebrates, such as mammals and birds. In zebrafish, this gene has been shown to be expressed in both osteoblasts and chondrocytes, but no study has reported its role in osteoblast development. To initially delineate the osteogenic program from chondrogenic lineage development, we used the zebrafish col10a1 promoter to establish a transgenic zebrafish expressing a GFP reporter specifically in osteoblast-specific bone structures that do not involve cartilaginous programs. A construct harboring a ∼2.2-kb promoter region was found to be sufficient to drive the reporter gene in osteoblast-specific bone structures within the endogenous col10a1 expression domain, confirming that separable cis-acting elements exist for distinct cell type-specific expression of col10a1 during zebrafish skeletal development. The ∼2.2-kb col10a1:GFP transgenic zebrafish marking only bone structures derived from osteoblasts will undoubtedly be an invaluable tool for identifying and characterizing molecular events driving osteoblast development in zebrafish, which may further provide a differential mechanism where col10a1 is involved in the development of chondrocytes undergoing maturation in other vertebrate systems.

NAD + Metabolism in Age-Related Hearing Loss

Age-related hearing loss (ARHL), a degenerative disorder characterized by age-dependent progressive increase in the threshold of auditory sensitivity, affects 40% of people over the age of 65, and it has emerged as an important social and public health problem. Various factors, including genetic and environmental components, are known to affect both the onset and severity of ARHL. In particular, age-dependent changes in cellular oxidative stress and inflammatory responses accompanied by altered cellular signaling and gene expression progressively affect the function of the auditory system and eventually lead to hearing impairment. Recent findings suggest that a disturbance of intracellular NAD(+) levels is clinically related to the progression of age-associated disorders. Therefore, maintenance of optimal intracellular NAD(+) levels may be a critical factor for cellular senescence, and thus, understanding its molecular signaling pathways would provide critical insights into the prevention and treatment of ARHL as well as other age-related diseases. In this review, we describe the role of NAD(+) metabolism in aging and age-related diseases, including ARHL, and discuss a potential strategy for prevention or treatment of ARHL with a particular interest in NAD(+)-dependent cellular pathways.

Fenofibrate exerts protective effects against gentamicin-induced toxicity in cochlear hair cells by activating antioxidant enzymes

Fenofibrate, an activator of peroxisome proliferator-activated receptors (PPARs), has been shown to protect the kidneys and brain cells from oxidative stress; however, its role in preventing hearing loss has not been reported to date, at least to the best of our knowledge. In this study, we demonstrated the protective effects of fenofibrate against gentamicin (GM)-induced ototoxicity. We found that the auditory brainstem response threshold which was increased by GM was significantly reduced by pre-treatment with fenofibrate in rats. In cochlear explants, the disruption of hair cell layers by GM was also markedly attenuated by pre-treatment with fenofibrate. In addition, fenofibrate almost completely abolished GM-induced reactive oxygen species generation, which seemed to be mediated at least in part by the restoration of the expression of PPAR-α-dependent antioxidant enzymes, including catalase and superoxide dismutase (SOD)-1. Of note, fenofibrate markedly increased the expression of heme oxygenase-1 (HO-1) which was also induced to a certain degree by GM alone. The induced expression of HO-1 by fenofibrate appeared to be essential for mediating the protective effects of fenofibrate, as the inhibition of HO-1 activity significantly diminished the protective effects of fenofibrate against the GM-mediated death of sensory hair cells in cochlea explant culture, as well as in zebrafish neuromasts. These results suggest that fenofibrate protects sensory hair cells from GM-induced toxicity by upregulating PPAR-α-dependent antioxidant enzymes, including HO-1. Our results provide insight into the preventive therapy for hearing loss caused by aminoglycoside antibiotics.

Fis1 depletion in osteoarthritis impairs chondrocyte survival and peroxisomal and lysosomal function

Cumulative evidence suggests the importance of organelle homeostasis in regulating metabolic functions in response to various cellular stresses. Particularly, the dynamism and health of the mitochondria-peroxisome network through fission and fusion are essential for cellular function; dysfunctional dynamism underlies the pathogenesis of several degenerative diseases including Parkinson’s disease. Here, we investigated the role of Fis1 in cartilage homeostasis and its relevance to osteoarthritis (OA). We found that Fis1 is significantly suppressed in human OA chondrocytes compared to that in normal chondrocytes. Fis1 depletion through siRNA induced peroxisomal dysfunction. Moreover, Fis1 suppression altered miRNA profiles, especially those implicated in lysosomal regulation. Lysosomal destruction using LAMP-1-specific targeted nanorods or lysosomal dysfunction through chloroquine treatment resulted in enhanced chondrocyte apoptosis and/or suppression of autophagy. Accordingly, lysosomal activity and autophagy were severely decreased in OA chondrocytes despite abundant LAMP-1-positive organelles. Moreover, Fis1 morpholino-injected zebrafish embryos displayed lysosome accumulation, mitochondrial dysfunction, and peroxisome reduction. Collectively, these data suggest interconnected links among Fis1-modulated miRNA, lysosomes, and autophagy, which contributes to chondrocyte survival/apoptosis. This study represents the first functional study of Fis1 with its pathological relevance to OA. Our data suggest a new target for controlling cartilage-degenerative diseases, such as OA.Key messageFis1 suppression in OA chondrocytes induces accumulation and inhibition of lysosomes.Fis1 suppression alters miRNAs, especially those implicated in lysosomal regulation.Lysosomal destruction results in chondrocyte apoptosis and suppression of autophagy.Fis1 depletion in zebrafish causes lysosome accumulation, mitochondrial dysfunction, and peroxisome reduction.This is the first functional study of Fis1 and its pathological relevance to OA.

Farnesol Has an Anti-obesity Effect in High-Fat Diet-Induced Obese Mice and Induces the Development of Beige Adipocytes in Human Adipose Tissue Derived-Mesenchymal Stem Cells

Brown adipocytes dissipate energy as heat and hence have an important therapeutic capacity for obesity. Development of brown-like adipocytes (also called beige) is also another attractive target for obesity treatment. Here, we investigated the effect of farnesol, an isoprenoid, on adipogenesis in adipocytes and on the browning of white adipose tissue (WAT) as well as on the weight gain of high-fat diet (HFD)-induced obese mice. Farnesol inhibited adipogenesis and the related key regulators including peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α through the up-regulation of AMP-activated protein kinase in 3T3-L1 murine adipocytes and human adipose tissue-derived mesenchymal stem cells (hAMSCs). Farnesol markedly increased the expression of uncoupling protein 1 and PPARγ coactivator 1 α in differentiated hAMSCs. In addition, farnesol limited the weight gain in HFD obese mice and induced the development of beige adipocytes in both inguinal and epididymal WAT. These results suggest that farnesol could be a potential therapeutic agent for obesity treatment.

Chrysophanic Acid Suppresses Adipogenesis and Induces Thermogenesis by Activating AMP-activated Protein Kinase Alpha in vivo and in vitro

Chrysophanic acid (CA) is a member of the anthraquinone family abundant in rhubarb, a widely used herb for obesity treatment in Traditional Korean Medicine. Though several studies have indicated numerous features of CA, no study has yet reported the effect of CA on obesity. In this study, we tried to identify the anti-obesity effects of CA. By using 3T3-L1 adipocytes and primary cultured brown adipocytes as in vitro models, high-fat diet (HFD)-induced obese mice, and zebrafish as in vivo models, we determined the anti-obesity effects of CA. CA reduced weight gain in HFD-induced obese mice. They also decreased lipid accumulation and the expressions of adipogenesis factors including peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα) in 3T3-L1 adipocytes. In addition, uncoupling protein 1 (UCP1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), the brown fat specific thermogenic genes, were up-regulated in brown adipocytes by CA treatment. Furthermore, when co-treated with Compound C, the AMP-activated protein kinase (AMPK) inhibitor, the action of CA on AMPKα was nullified in both types of adipocytes, indicating the multi-controlling effect of CA was partially via the AMPKα pathway. Given all together, these results indicate that CA can ameliorate obesity by controlling the adipogenic and thermogenic pathway at the same time. On these bases, we suggest the new potential of CA as an anti-obese pharmacotherapy.

Erdosteine protects HEI-OC1 auditory cells from cisplatin toxicity through suppression of inflammatory cytokines and induction of Nrf2 target proteins.

Cisplatin has many adverse effects, which are a major limitation to its use, including ototoxicity, neurotoxicity, and nephrotoxicity. This study aims to elucidate the protective mechanisms of erdosteine against cisplatin in HEI-OC1 cells. Pretreatment with erdosteine protects HEI-OC1 cells from cisplatin-medicated apoptosis, which is characterized by increase in nuclear fragmentation, DNA laddering, sub-G0/G1 phase, H2AX phosphorylation, PARP cleavage, and caspase-3 activity. Erdosteine significantly suppressed the production of reactive nitrogen/oxygen species and pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in cisplatin-treated cells. Studies using pharmacologic inhibitors demonstrated that phosphatidylinositol-3-kinases (PI3K) and protein kinase B (Akt) have protective roles in the action of erdosteine against cisplatin in HEI-OC1 cells. In addition, pretreatment with erdosteine clearly suppressed the phosphorylation of p53 (Ser15) and expression of p53-upregulated modulator of apoptosis. Erdosteine markedly induces expression of NF-E2-related factor 2 (Nrf2), which may contribute to the increase in expression of glutathione redox genes γ-l-glutamate-l-cysteine-ligase catalytic and γ-l-glutamate-l-cysteine-ligase modifier subunits, as well as in the antioxidant genes HO-1 and SOD2 in cisplatin-treated HEI-OC1 cells. Furthermore, the increase in expression of phosphorylated p53 induced by cisplatin is markedly attenuated by pretreatment with erdosteine in the mitochondrial fraction. This increased expression may inhibit the cytosolic expression of the apoptosis-inducing factor, cytochrome c, and Bax/Bcl-xL ratio. Thus, our results suggest that treatment with erdosteine is significantly attenuated cisplatin-induced damage through the activation of Nrf2-dependent antioxidant genes, inhibition of pro-inflammatory cytokines, activation of the PI3K/Akt signaling, and mitochondrial-related inhibition of pro-apoptotic protein expression in HEI-OC1 auditory cells.