Synthesis and evaluation of in vitro antioxidant capacities of some benzimidazole derivatives

New, except 1d, melatonin analogue benzimidazole derivatives were synthesized and characterized in the present study. The potential role of melatonin as an antioxidant by scavenging and detoxifying ROS raised the possibility that compounds that are analogous to melatonin can also be used for their antioxidant properties. Therefore the antioxidant effects of the newly synthesized compounds were investigated in vitro by means of their inhibitory effect on hydrogen peroxide-induced erythrocyte membrane lipid peroxidation (EMLP) and on various erythrocyte antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PD). The synthesized benzimidazole derivatives showed remarkable antioxidant activity in vitro in the H₂O₂-induced EMLP system. Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships.     

Peptidic nanoparticles: for cancer diagnosis and therapy

A challenging topic in cancer research is to create drug delivery system that can bring in a specific and noncytotoxic manner a therapeutic compound. Usually, tumor targeting requires very specific compounds. Currently, peptide analogues like somatostatin, neurotensin, or bombesin are used to target G-coupled receptors, which are overexpressed on tumor cells. However, many of those analogues are rapidly degraded in the plasma and are cytotoxic [1–2]. Due to the limited efficiency and high toxicity of conventional chemotherapy different strategies have been developed for non-cytotoxic cancer treatment and cancer localization [3–5]. The recent development in bio-nanotechnology offers new avenues for cancer therapy. A lot of studies have been devoted to nanoparticulate delivery systems (10–100nm) like lipid or polymer particles [6–8]. Due to the nanometer sized of such cargos, the transportation of therapeutic compounds in the blood stream is increased in terms of time circulation. But their surface functionalization to improve drug-targeting properties is usually complicated and rather uneffective. We have recently designed a novel type of functional nanoparticles with regular icosahedral symmetry, mimicking small, rigid viral capsids (Fig. 1 (A)) and a diameter of about 17 nm (Fig. 1 (C)) which self-assemble from single polypeptide chains (Fig. 1 (B)).     

Role of C-reactive protein in complement-mediated hemolysis in Malaria

Human C-reactive protein (CRP) is a clinically important classical acute phase protein. Although CRP has been reported to bind with many nucleated cells, the direct binding of CRP to erythrocytes in diseases remains largely unexplored. The main focus of the present study was to investigate the binding of disease-specific CRP to erythrocytes of same patients. Distinct molecular variant of disease-specific CRP was affinity purified from sera of malaria patients (CRP_Mal). This CRP showed strong binding with malaria erythrocytes (RBC_Mal) as confirmed by flow cytometric analysis (FACS), enzyme-linked immunosorbent assays (ELISA), and radio binding assays. Calcium and phosphoryl choline (PC) were found to be essential for this interaction. A 2.3-fold increased binding of induced CRP to RBC_Mal as compared to normal erythrocytes (RBC_N) confirmed disease-specificity. Preincubation of RBC_Mal with unconjugated CRP showed 3–5 fold inhibition. The association constant of CRP and RBC_Mal was 4.7 × 10⁶ cpm/μg with the corresponding number of receptors/cell being 4.3 × 10⁵. The effector function of CRP_Mal has been demonstrated by its potency to activate the complement pathway. An optimal dose of 10 μg/ml of CRP induced three-fold higher hemolysis of patient erythrocytes as compared to RBC_N. These studies provide direct evidence for an important phagocytic functional interaction of this acute-phase protein by triggering the CRP-complement pathway after the binding of CRP_Mal with RBC_Mal. Hemolysis as triggered by this pathway may be one of the causative factors of anemia, a common clinical manifestation of this disease.     

Natural antioxidants attenuate mycolactone toxicity to RAW 264.7 macrophages

Mycobacterium ulcerans produces a macrolide exotoxin, mycolactone which suppresses immune cells activity, is toxic to most cells and the key virulence factor in the pathogenesis of Buruli ulcer disease. Mycolactone is reported to mediate the production of reactive oxygen species in keratinocytes; cells that play critical role in wound healing. Increased levels of reactive oxygen species have been shown to disrupt the well-ordered process of wound repair; hence, the function of wound-healing cells such as macrophages, keratinocytes, and fibroblast could be impaired in the presence of the reactive oxygen species mediator, mycolactone. To ensure regeneration of tissues in chronic ulcers, with proper and timely healing of the wounds, natural antioxidants that can combat the effects of induced reactive oxygen species in wound-healing cells ought to be investigated. Reactive oxygen species activity was determined in mycolactone-treated RAW 264.7 macrophages and the scavenging ability of the antioxidants (ascorbic acid, gallic acid, and green tea kombucha) against mycolactone-induced reactive oxygen species (superoxide anions) was assessed using fluorescein probe (DCF-DA) and nitroblue tetrazolium dye. Cytotoxicity of the antioxidants, mycolactone, and the protective effect of the antioxidants on the cells upon treatment with mycolactone were determined using the Alamar blue assay. The expression levels of endogenous antioxidant enzyme genes (superoxide dismutase, catalase, and glutathione peroxidase) in response to mycolactone-mediated reactive oxygen species were determined using RT-qPCR. Mycolactone induced the production of reactive oxygen species in RAW 264.7 macrophages, and the resulting superoxide anions were scavenged by some of the antioxidants. The selected endogenous antioxidant enzyme genes in the macrophages were upregulated in the presence of the antioxidants and mycolactone. The exogenously supplied ascorbic acid and green tea kombucha offered moderate protection to the macrophages against the toxicity of mycolactone. We conclude that the results provide insights into alternate and adjunct therapeutic approaches in Buruli ulcer treatment, which could significantly attenuate the toxicity of the pathogenic factor; mycolactone.     

Intronic gene conversion in the evolution of human X-linked color vision genes

Human red and green visual pigment genes are X-linked duplicate genes. To study their evolutionary history, introns 2 and 4 (1,987 and 1,552 bp, respectively) of human red and green pigment genes were sequenced. Surprisingly, we found that intron 4 sequences of these two genes are identical and that the intron 2 sequences differ by only 0.3%. The low divergences are unexpected because the duplication event producing the two genes is believed to have occurred before the separation of the human and Old World monkey (OWM) lineages. Indeed, the divergences in the two introns are significantly lower than both the synonymous divergence (3.2% +/- 1.1%) and the nonsynonymous divergence (2.0% +/- 0.5%) in the coding sequences (exons 1-6). A comparison of partial sequences of exons 4 and 5 of human and OWM red and green pigment genes supports the hypothesis that the gene duplication occurred before the human-OWM split. In conclusion, the high similarities in the two intron sequences might be due to very recent gene conversion, probably during evolution of the human lineage.