Chemopreventive effect of <Emphasis Type="BoldItalic">Padina boergesenii</Emphasis> extracts on ferric nitrilotriacetate (Fe-NTA)-induced oxidative damage in Wistar rats

The present study was designed to investigate the prophylactic effect of extracts of the brown alga Padina boergesenii against potent nephrotoxic agent ferric nitrilotriacetate (Fe-NTA), in blood circulation of rats. Administration of Fe-NTA for seven consecutive days significantly enhanced lipid peroxidation accompanied with reduction in glutathione content. Together with this, the level of antioxidant enzymes, glutathione peroxidase, superoxide dismutase, and catalase was significantly (P < 0.05) diminished. Pretreatment of rats with P. boergesenii (150 mg kg⁻¹ body weight) reversed Fe-NTA-induced oxidative damage in lipid peroxidation and glutathione content significantly (P < 0.05). Further, the activity of antioxidant enzymes was also restored significantly. In order to assess the role of polyphenolic components in the relevant activity, phenolic contents of the extract was found to be 1.78 ± 0.02% in the methanol extract and 1.30 ± 0.30% in the diethyl ether extract. Hence, the present results confirm that the brown alga P. boergesenii preclude its role in Fe-NTA-induced oxidative damage and hyperproliferative response in circulation.     

Probing the self-association, intermolecular contacts, and folding propensity of amelogenin

Amelogenins are an intrinsically disordered protein family that plays a major role in the development of tooth enamel, one of the most highly mineralized materials in nature. Monomeric porcine amelogenin possesses random coil and residual secondary structures, but it is not known which sequence regions would be conformationally attractive to potential enamel matrix targets such as other amelogenins (self-assembly), other matrix proteins, cell surfaces, or biominerals. To address this further, we investigated recombinant porcine amelogenin (rP172) using "solvent engineering" techniques to simultaneously promote native-like structure and induce amelogenin oligomerization in a manner that allows identification of intermolecular contacts between amelogenin molecules. We discovered that in the presence of 2,2,2-trifluoroethanol (TFE) significant folding transitions and stabilization occurred primarily within the N- and C-termini, while the polyproline Type II central domain was largely resistant to conformational transitions. Seven Pro residues (P2, P127, P130, P139, P154, P157, P162) exhibited conformational response to TFE, and this indicates these Pro residues act as folding enhancers in rP172. The remaining Pro residues resisted TFE perturbations and thus act as conformational stabilizers. We also noted that TFE induced rP172 self-association via the formation of intermolecular contacts involving P4-H6, V19-P33, and E40-T58 regions of the N-terminus. Collectively, these results confirm that the N- and C-termini of amelogenin are conformationally responsive and represent potential interactive sites for amelogenin-target interactions during enamel matrix mineralization. Conversely, the Pro, Gln central domain is resistant to folding and this may have important functional significance for amelogenin.     

Super-Obese Patient-Derived iPSC Hypothalamic Neurons Exhibit Obesogenic Signatures and Hormone Responses

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The discovery and optimization of naphthalene-linked P2-P4 Macrocycles as inhibitors of HCV NS3 protease

Naphthalene-linked P2-P4 macrocycles within a tri-peptide-based acyl sulfonamide chemotype have been synthesized and found to inhibit HCV NS3 proteases representing genotypes 1a and 1b with single digit nanomolar potency. The pharmacokinetic profile of compounds in this series was optimized through structural modifications along the macrocycle tether as well as the P1 subsite. Ultimately a compound with oral bioavailability of 100% in rat, and a long half-life in plasma was obtained. However, compounds in this macrocyclic series exhibited cardiac effects in an isolated rabbit heart model and for this reason further optimization efforts were discontinued.     

Dendritic cells from C57BL/6 mice undergo activation and induce Th1-effector cell responses against Campylobacter jejuni

Food-borne Campylobacter jejuni (Cj) is an important cause of enteritis. We showed that C57BL/6 and congenic interleukin (IL)-10(-/-) mice serve as models of Cj colonization and enteritis, respectively. Thus, C57BL/6 mice are resistant to Cj induced disease. Because dendritic cells (DCs) are central to regulating adaptive immune responses, we investigated the interaction of Cj with murine bone marrow-derived DCs (BM-DCs) to assess bacterial killing, DC activation, and the ability of Cj-infected BM-DCs to stimulate Campylobacter-specific T cell responses in vitro. BM-DCs challenged with Cj efficiently internalized and killed Cj 11168 and significantly upregulated surface MHC-II, CD40, CD80 and CD86 demonstrating a mature phenotype. Infected BM-DCs secreted significant amounts of tumor necrosis factor-alpha (TNF-alpha), IL-6 and IL-12p70. Formalin-killed Cj also induced maturation of BM-DCs with similar cytokine production but at a significantly lower magnitude than live bacteria. Maximal activation of murine BM-DCs required internalization of Cj; attachment alone was not sufficient to elicit significant responses. Also, various strains of Cj elicited different magnitudes of cytokine production from BM-DCs. Finally, in a coculture system, Cj-infected BM-DCs induced high level interferon-gamma (INF-gamma) production from CD4+T cells indicating Th1 polarization. Thus, DCs from resistant C57BL/6 mice initiate T cell responses against Cj.     

Chlamydomonas reinhardtii secretes compounds that mimic bacterial signals and interfere with quorum sensing regulation in bacteria

The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-L-homoserine lactone (AHL) signal molecules used by many bacteria for quorum sensing regulation of gene expression. More than a dozen chemically separable but unidentified substances capable of specifically stimulating the LasR or CepR but not the LuxR, AhyR, or CviR AHL bacterial quorum sensing reporter strains were detected in ethyl acetate extracts of C. reinhardtii culture filtrates. Colonies of C. reinhardtii and Chlorella spp. stimulated quorum sensing-dependent luminescence in Vibrio harveyi, indicating that these algae may produce compounds that affect the AI-2 furanosyl borate diester-mediated quorum sensing system of Vibrio spp. Treatment of the soil bacterium Sinorhizobium meliloti with a partially purified LasR mimic from C. reinhardtii affected the accumulation of 16 of the 25 proteins that were altered in response to the bacterium's own AHL signals, providing evidence that the algal mimic affected quorum sensing-regulated functions in this wild-type bacterium. Peptide mass fingerprinting identified 32 proteins affected by the bacterium's AHLs or the purified algal mimic, including GroEL chaperonins, the nitrogen regulatory protein PII, and a GTP-binding protein. The algal mimic was able to cancel the stimulatory effects of bacterial AHLs on the accumulation of seven of these proteins, providing evidence that the secretion of AHL mimics by the alga could be effective in disruption of quorum sensing in naturally encountered bacteria.     

Comparative transcriptome analyses provide novel insights into the differential response of Pigeonpea (Cajanus cajan L.) and its wild relative (Cajanus platycarpus (Benth.) Maesen) to herbivory by Helicoverpa armigera (Hübner)

Plant Molecular Biology - We demonstrate that the C-terminus of OsCDC48 is essential for maintaining its full ATPase activity and OsCDC48/48E interaction is required to modulate cellular processes...     

Dysregulated expression of microRNAs in aqueous humor from intraocular tuberculosis patients

Molecular Biology Reports - Systemic Mycobacterium tuberculosis (Mtb) infection alters microRNA’s expression that controls cellular processes and modulates host defense mechanisms. However,...     

The vitamin riboflavin and its derivative lumichrome activate the LasR bacterial quorum-sensing receptor

Many bacteria use quorum sensing (QS) as an intercellular signaling mechanism to regulate gene expression in local populations. Plant and algal hosts, in turn, secrete compounds that mimic bacterial QS signals, allowing these hosts to manipulate QS-regulated gene expression in bacteria. Lumichrome, a derivative of the vitamin riboflavin, was purified and chemically identified from culture filtrates of the alga Chlamydomonas as a QS signal-mimic compound capable of stimulating the Pseudomonas aeruginosa LasR QS receptor. LasR normally recognizes the N-acyl homoserine lactone (AHL) signal, N-3-oxo-dodecanoyl homoserine lactone. Authentic lumichrome and riboflavin stimulated the LasR receptor in bioassays and lumichrome activated LasR in gel shift experiments. Amino acid substitutions in LasR residues required for AHL binding altered responses to both AHLs and lumichrome or riboflavin. These results and docking studies indicate that the AHL binding pocket of LasR recognizes both AHLs and the structurally dissimilar lumichrome or riboflavin. Bacteria, plants, and algae commonly secrete riboflavin or lumichrome, raising the possibility that these compounds could serve as either QS signals or as interkingdom signal mimics capable of manipulating QS in bacteria with a LasR-like receptor.     

Structure-function relationship of avian eggshell matrix proteins: a comparative study of two major eggshell matrix proteins, ansocalcin and OC-17

The role of individual matrix proteins in avian eggshell calcification is poorly understood despite numerous attempts to characterize and localize their presence in the eggshell matrix. Ansocalcin, the major matrix protein from goose eggshell, was found to induce the formation of calcite crystal aggregates under in vitro. Owing to its high similarity with the chicken eggshell matrix protein ovocleidin 17 (OC-17), a comparative investigation has been carried out to understand the structure-function relationship. RP-HPLC shows that ansocalcin is the major component in extracts of goose eggshells before and after bleach treatment. However, OC-17 was observed in minute quantities in the extract of bleach-treated chicken eggshells. In vitro crystal growth experiments showed that OC-17 and ansocalcin interact differently with the calcite crystals formed. Circular dichroism, intrinsic tryptophan fluorescence, and dynamic light scattering studies showed that, under the conditions used in our experiments, OC-17 does not aggregate in solution or induce the nucleation of calcite aggregates in the concentration range used. These observations indicate that OC-17 and ansocalcin play different roles in the eggshell calcification. To our knowledge, this is the first report on the comparison of properties of homologous eggshell proteins that belong to the same phylogeny.