Assessment of Synthesis Machinery of Two Antimicrobial Peptides from Paenibacillus alvei NP75

Paenibacillus alvei NP75, a Gram-positive bacterium, produces two different antimicrobial peptides, paenibacillin N and P, which has potent antimicrobial activity against many clinical pathogens. The synthesis pattern of these antimicrobial peptides by P. alvei NP75 was studied extensively. The results were outstanding in a way that the paenibacillin N was synthesized irrespective of the growth of bacteria (non-ribosomal mediated), whereas paenibacillin P production was carried out by ribosomal mediated. In addition to the antimicrobial peptides, P. alvei NP75 also produces an immunogenic extracellular protease to defend itself from its own antimicrobial peptide, paenibacillin P. Furthermore, this immunogenic protease production was impaired by the addition of protease inhibitor, phenylmethylsulfonyl fluoride (PMSF). The sodium dodecyl sulfate (SDS) treated strain (mutant) failed to produce paenibacillin P, whereas the production of neither paenibacillin N nor the protease was affected by the plasmid curing. The plasmid curing studies that divulge the genes responsible for the synthesis of paenibacillin N and protease were found to be genome encoded, and paenibacillin P was plasmid encoded. We are reporting, first of its kind, the co-production of two different antimicrobial peptides from P. alvei NP75 through non-ribosomal and ribosomal pathways that could be used as effective antibiotics.

     

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)--induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T₃), thyroxine (T₄), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3β-hydroxysteroid dehydrogenase (3β-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P₄₅₀ side chain cleavage enzyme (P₄₅₀scc), 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamyl transpeptidase (γ-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T₃, T₄, testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P₄₅₀scc, 3β-HSD, 17β-HSD, antioxidant enzymes SOD, CAT, GPX, GR, γ-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.     

Accumulation of lipid peroxidation-derived DNA lesions: potential lead markers for chemoprevention of inflammation-driven malignancies

Chronic inflammatory processes produce an excess of ROS and DNA-reactive aldehydes from lipid peroxidation (LPO), such as trans-4-hydroxy-2-nonenal (HNE) and malondialdehyde (MDA), which can modify cellular macromolecules and drive to malignancy. Etheno-modified DNA bases are generated inter alia by reaction of DNA with the major LPO product, HNE. We are investigating steady-state levels of etheno-DNA adducts in organs with diseases related to persistent inflammatory processes that can lead to malignancies. We have developed ultrasensitive and specific methods for the detection of etheno-DNA base adducts in human tissues and in urine. Etheno-DNA adduct levels were found to be significantly elevated in the affected organs of subjects with chronic pancreatitis, ulcerative colitis and Crohn's disease. When patients with alcohol abuse-related hepatitis, fatty liver, fibrosis and cirrhosis were compared with asymptomatic livers, excess hepatic DNA damage was seen in the three latter patient groups. Etheno-deoxyadenosine excreted in urine was measured in HBV-infected patients diagnosed with chronic hepatitis, cirrhosis and hepatocellular carcinoma. As compared to controls, these patients had up to 90-fold increased urinary levels. Impaired or imbalanced DNA-repair pathways may influence the steady-state levels of etheno-DNA adducts in inflamed tissues. In conclusion, etheno-DNA adducts may serve as potential lead markers for assessing progression of inflammatory cancer-prone diseases. If so, the efficacy of human chemopreventive interventions for malignant disease prevention could be verified.     

N-terminal Gly(224)-Gly(411) domain in Listeria adhesion protein interacts with host receptor Hsp60

Background

Listeria adhesion protein (LAP) is a housekeeping bifunctional enzyme consisting of N-terminal acetaldehyde dehydrogenase (ALDH) and C-terminal alcohol dehydrogenase (ADH). It aids Listeria monocytogenes in crossing the epithelial barrier through a paracellular route by interacting with its host receptor, heat shock protein 60 (Hsp60). To gain insight into the binding interaction between LAP and Hsp60, LAP subdomain(s) participating in the Hsp60 interaction were investigated.

Methods

Using a ModBase structural model, LAP was divided into 4 putative subdomains: the ALDH region contains N1 (Met₁–Pro₂₂₃) and N2 (Gly₂₂₄–Gly₄₁₁), and the ADH region contains C1 (Gly₄₁₂–Val₆₄₈) and C2 (Pro₆₄₉–Val₈₆₆). Each subdomain was cloned and overexpressed in Escherichia coli and purified. Purified subdomains were used in ligand overlay, immunofluorescence, and bead-based epithelial cell adhesion assays to analyze each domain''s affinity toward Hsp60 protein or human ileocecal epithelial HCT-8 cells.

Results

The N2 subdomain exhibited the greatest affinity for Hsp60 with a K _D of 9.50±2.6 nM. The K _D of full-length LAP (7.2±0.5 nM) to Hsp60 was comparable to the N2 value. Microspheres (1 µm diameter) coated with N2 subdomain showed significantly (P<0.05) higher binding to HCT-8 cells than beads coated with other subdomains and this binding was inhibited when HCT-8 cells were pretreated with anti-Hsp60 antibody to specifically block epithelial Hsp60. Furthermore, HCT-8 cells pretreated with purified N2 subdomain also reduced L. monocytogenes adhesion by about 4 log confirming its involvement in interaction with epithelial cells.

Conclusion

These data indicate that the N2 subdomain in the LAP ALDH domain is critical in initiating interaction with mammalian cell receptor Hsp60 providing insight into the molecular mechanism of pathogenesis for the development of potential anti-listerial control strategies.     

Exocyclic DNA adducts as oxidative stress markers in colon carcinogenesis: potential role of lipid peroxidation,dietary fat and antioxidants

Molecular pathways to colorectal cancer involve multiple genetic changes, whereby extensive oxyradical damage causes mutations in cancer-related genes and leads to a cycle of cell death and regeneration. Besides direct oxidative DNA-damage, reactive oxygen and nitrogen species can induce etheno (epsilon)-DNA adducts mainly via trans-4-hydroxy-2-nonenal, generated as the major aldehyde by lipid peroxidation (LPO) of omega-6 PUFAs. Patients with familial adenomatous polyposis (FAP) develop multiple colorectal adenomas. In affected tissues increased LPO could be triggered due to increased arachidonic acid metabolism as a result of elevated cyclooxygenases. Our studies demonstrated an increased epsilon-DNA adduct level in affected colon epithelia of FAP patients. Epsilon-DNA adducts are promutagenic and can cause genomic instability that drives colorectal adenoma to malignancy. We have further investigated the potential chemopreventive properties of olive oil and its polyphenolic components. 'Mediterranean diet', of which olive oil is a major fatty acid source, has protective effects against human breast and colorectal cancers. Olive oil extracts and the newly identified lignan fractions showed high antioxidant capacity in vitro. As epsilon-DNA adducts are biomarkers for oxidative stress and LPO induced DNA damage, they can verify the efficacy of newly identified antioxidants, e.g. from olive oil, as chemopreventive agents against colon carcinogenesis.