Epigenetics and oxidative stress: A twin-edged sword in spermatogenesis.

Spermatogenesis is a series of complex events involving a delicate balance between cell proliferation and cell differentiation. Aggregation of chromatins and epigenetic modifications play a vital role in spermatogenesis via regulation of molecular pathways to maintain testicular homeostasis. These epigenetic mechanisms consist of histone modification, chromatin remodelling, DNA methylation and miRNA, etc., which reportedly are critical players in spermatogenesis. One such mechanism involves regulation of oxidative stress in the male reproductive system. The fact that testicular cells contain plenty of unsaturated fatty acids and undergo division at a high rate makes spermatogenic cells highly susceptible to oxidative insult leading to deleterious effect on spermatozoa, which may culminate in infertility in men. Although the correlation between ROS-mediated oxidative stress and epigenetic alterations has been indicated, research in this regard is still in infancy. Further, the fact that environmental and life style factors are critical determinants of spermatogenic potential indicates the importance of epigenetic regulation of key molecular events in spermatogenesis. Therefore, the current review aims to discuss the ROS-induced epigenetic deregulation of the molecular mechanism(s) involved in spermatogenesis.

Chemopreventive action of Imatinib, a tyrosine kinase inhibitor in the regulation of angiogenesis and apoptosis in rat model of lung cancer.

The present study explored the events of angiogenesis and apoptosis in 7,12-dimethyl benz(a)anthracene (DMBA)-induced lung cancer in rat and its chemoprevention with Imatinib, a receptor tyrosine kinase inhibitor. Further, it includes  lipopolysaccharide (LPS) mediating inflammation along with DMBA for the promotion of lung carcinogenesis. The animals received a single intratracheal instillation of DMBA (20 mg/kg body weight) in olive oil and LPS (0.6 mg/kg body weight) to induce tumors in 16 weeks. Besides morphology and histology of the lung tissues, RT-PCR, western blots, and immunofluorescence were performed for the expression of apoptotic and angiogenic proteins. Apoptosis was studied by mitochondrial Bcl-2/Bax ratio and staining with the dyes Acridine orange/ethidium bromide of the isolated Broncho epithelial cells. Also, mitochondrial membrane potential (ΔΨM) was studied by JC-1. The study revealed that the expression of VEGF, MMP-2, MMP-9, and the chemokine MCP-1 to be very high in DMBA and DMBA + LPS groups, while Bcl-2 also shows an elevated expression. These results were restored with Imatinib treatment. The pro-apoptotic proteins, Bax, Bad, Apaf-1, and Caspase-3 were highly diminished in DMBA and DMBA + LPS groups which were recovered with Imatinib treatment.

Role of GSK-3ß in Regulation of Canonical Wnt/ß-catenin Signaling and PI3-K/Akt Oncogenic Pathway in Colon Cancer.

Non-steroidal anti-inflammatory drugs (NSAIDs) are emerging as novel chemopreventive agents because of their ability in blocking cellular proliferation, and thereby tumor development, and also by promoting apoptosis. GSK-3ß, a serine threonine kinase and a negative regulator of the oncogenic Wnt/ß-catenin signaling pathway, plays a critical role in the regulation of oncogenesis. Celecoxib and etoricoxib, the two cyclooxygenase-2 (COX-2) selective NSAIDs, and Diclofenac, a preferential COX-2 inhibitory NSAID, had shown uniformly the chemopreventive and anti-neoplastic effects in the early stage of colon cancer by promoting apoptosis as well as an over-expression of GSK-3ß while down-regulating the PI3-K/Akt oncogenic pathway.

Selenium-Based Novel Epigenetic Regulators Offer Effective Chemotherapeutic Alternative with Wider Safety Margins in Experimental Colorectal Cancer.

Colorectal cancer (CRC) is a major cause of morbidity and mortality worldwide. Despite the critical involvement of epigenetic modifications in CRC, the studies on the chemotherapeutic efficacy of various epigenetic regulators remain limited. Considering the key roles of histone deacetylases (HDACs) in the regulation of diverse cellular processes, several HDAC inhibitors are implied as effective therapeutic strategies. In this context, suberoylanilide hydroxamic acid (SAHA), a 2nd-generation HDAC inhibitor, showed limited efficacy in solid tumors. Also, side effects associated with SAHA limit its clinical application. Based on the redox-modulatory and HDAC inhbitiory activities of essential trace element selenium (Se), the anti-carcinogenic potential of Se substituted SAHA, namely, SelSA-1 (25 mg kg-1), was screened for it enhanced anti-tumorigenic role and wider safety profiles in DMH-induced CRC in Balb/c mice. A multipronged approach such as in silico, biochemical, and pharmacokinetics (PK) has been used to screen, characterize, and evaluate these novel compounds in comparison to existing HDAC inhibitor SAHA. This is the first in vivo study indicating the chemotherapeutic potential of Se-based novel epigenetic regulators such as SelSA-1 in any in vivo experimental model of carcinogenesis. Pharmcological and toxicity data indicated better safety margins, bioavailability, tolerance, and elimination rate of SelSA-1 compared to classical HDAC inhibitor SAHA. Further, histological and morphological evidence demonstrated enhanced chemotherapeutic potential of SelSA-1 even at lower pharmacological doses than SAHA. This is the first in vivo study suggesting Se-based novel epigenetic regulators as potential chemotherapeutic alternatives with wider safety margins and enhanced anticancer activities.

Selenium Ameliorates Ibuprofen Induced Testicular Toxicity by Redox Regulation: Running Head: Se protects against NSAID induced testicular toxicity.

Despite the Cox inhibitory anti-inflammatory and antipyretic effects of most widely used non-steroidal anti-inflammatory drugs (NSAIDs), such as Ibuprofen, their chronic use is associated with a plethora of patho-physiological insults. One such toxic effect on testicular tissues is not well studied and the underlying molecular mechanisms remain unexplored. Thus, the current study is designed to evaluate the antioxidant properties of essential trace element selenium (Se) to ameliorative Ibuprofen associated testicular toxic effects. Adult male Wistar rats were divided into 3 groups and fed on diets containing different concentrations of sodium selenite, viz. 0.01 mg/kg (Se- deficient), 0.2 mg/kg (Se-adequate), or 0.5 mg/kg (Se- supplemented) for 8 weeks. After diet feeding schedule, each group was divided into two subgroups i.e., with or without the treatment of Ibuprofen (120 mg/kg Bw). The protective effect of Se was evaluated by measuring testicular Se and selenoproteins status, spermatogenic markers, histopathology and testicular redox status. Ibuprofen diminished seminal volume, sperm count, sperm motility, which correlated well increased testicular reactive oxygen species. Se deficiency exacerbated these detrimental effects of ibuprofen by increasing oxidative stress. Alternatively, Se supplementation through antioxidant enzymes mediated protective effects. Se as essential antioxidant selenoproteins ameliorates Ibuprofen induced male reproductive toxicity.

Protective Role of Selenium Against Hemolytic Anemia Is Mediated Through Redox Modulation.

Selenium (Se), an essential trace element and potent nutritional antioxidant, exerts its biological effects through incorporation into selenoproteins like glutathione peroxidase (GPx). Modest decrement in the levels of GPx could be partly responsible for peroxidation of RBCs, which results into hemolytic anemia. Therefore, it is hypothesized that dietary Se, as selenoproteins (GPx), can maintain the homeostasis in RBCs and regulate the erythropoiesis by preventing oxidative stress-mediated hemolysis. Se-deficient (0.01 ppm), Se-adequate (0.1 ppm sodium selenite), and Se-supplemented (0.5 ppm sodium selenite) status were created in Balb/c mice by feeding yeast-based diets for 8 weeks and established by measuring Se levels in plasma and activities, expressions of Se-dependent selenoproteins. Fifty percent of mice from each differential Se group were treated with phenylhydrazine (PHZ, 20 mg/kg, i.p.) to induce hemolytic anemia. Results indicated that PHZ-treated Se-deficient animals demonstrated increased hemolysis, abnormal RBC morphology, increase in Heinz bodies and reticulocytes, and denaturation of hemoglobin to globin precipitates and methemoglobin. Se supplementation protected against these hemolytic changes and makes RBCs less fragile. These findings were consistent with dietary Se concentration-dependent changes in activity and expression of GPx indicating that ROS-mediated oxidative stress is integral to hemolysis. Protective effects of Se supplementation against increased levels of ROS, protein carbonyls, and peroxide damage to membrane lipids and enzymatic antioxidants validated these observations. In conclusion, dietary Se supplementation protected the RBCs against hemolysis by mitigating ROS-mediated oxidative stress.

Chemopreventive action of non-steroidal anti-inflammatory drugs on the inflammatory pathways in colon cancer.

Non-steroidal anti-inflammatory drugs (NSAIDs) are emerging as novel chemopreventive agents against a variety of cancers owing to their capability in blocking the tumor development by cellular proliferation and by promoting apoptosis. Inflammation is principal cause of colon carcinogenesis. A missing link between inflammation and cancer could be the activation of NF-κB, which is a hallmark of inflammatory response, and is commonly detected in malignant tumors. Therefore, targeting pro-inflammatory cyclooxygenase enzymes and transcription factors will be profitable as a mechanism to inhibit tumor growth. In the present study, we have studied the role of various pro-inflammatory enzymes and transcription factors in the development of the 1,2-dimethylhydrazine dihydrochloride (DMH)-induced colorectal cancer and also observed the role of three NSAIDs, viz., Celecoxib, Etoricoxib and Diclofenac. Carcinogenic changes were observed in morphological and histopathological studies, whereas protein regulations of various biomolecules were identified by immunofluorescence analysis. Apoptotic studies was done by TUNEL assay and Hoechst/PI co-staining of the isolated colonocytes. It was found that DMH-treated animals were having an over-expression of pro-inflammatory enzymes, aberrant nuclear localization of activated cell survival transcription factor, NF-κB and suppression of anti-inflammatory transcription factor PPAR-γ, thereby suggesting a marked role of inflammation in the tumor progression. However, co-administration of NSAIDs has significantly reduced the inflammatory potential of the growing neoplasm.

Chemoprevention of Colon Cancer through Inhibition of Angiogenesis and Induction of Apoptosis by Nonsteroidal Anti-Inflammatory Drugs.

Cancer cells require nourishment for the growth of the primary tumor mass and spread of the metastatic colony. These needs are fulfilled by tumor-associated neovasculature known as angiogenesis, which also favors the transition from hyperplasia to neoplasia, that is, from a state of cellular multiplication to uncontrolled proliferation. Therefore, targeting angiogenesis is profitable as a mechanism to inhibit tumor growth. Furthermore, it is important to understand the cross-communication between vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs) in the neoplastic and proinflammatory milieu. We studied the role of two important chemokines (monocyte chemoattractant protein-1 [MCP-1] and macrophage inflammatory protein-1ß [MIP-1ß]) along with VEGF and MMPs in nonsteroidal anti-inflammatory drug (NSAID)-induced chemopreventive effects in experimental colon cancer in rats. 1,2-Dimethylhydrazine dihydrochloride (DMH) was used as cancer-inducing agent and three NSAIDs (celecoxib, etoricoxib, and diclofenac) were given orally as chemopreventive agents. Analysis by immunofluorescence and western blotting shows that the expression of VEGF, MMP-2, and MMP-9 was found to be significantly elevated in the DMH- treated group and notably lowered by NSAID coadministration. The expression of MCP-1 was found to be markedly decreased, whereas that of MIP-1ß increased after NSAID coadministration. NSAID coadministration was also able to induce apoptosis, confirmed using studies by Hoechst/propidium iodide (PI) costaining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Results from the present study indicate the potential role of these chemokines along with VEGF and MMPs against angiogenesis in DMH-induced cancer. The inhibition of angiogenesis and induction of apoptosis by NSAIDs were found to be possible mechanisms in the chemoprevention of colon cancer.