Mimicry of native peptide antigens by the corresponding retro-inverso analogs is dependent on their intrinsic structure and interaction propensities

Retro-inverso (ri) analogs of model T cell and B cell epitopes were predictively designed as mimics and then assayed for activity to understand the basis of functional ri-antigenic peptide mimicry. ri versions of two MHC class I binding peptide epitopes, one from a vesicular stomatitis virus glycoprotein (VSV(p)) and another from OVA (OVAp), exhibit structural as well as functional mimicry of their native counterparts. The two ri peptides exhibit conformational plasticity and they bind to MHC class I (H-2K(b)) similar to their native counterparts both in silico and in vivo. In fact, ri-OVAp is also presented to an OVAp-specific T cell line in a mode similar to native OVAp. In contrast, the ri version of an immunodominant B cell peptide epitope from a hepatitis B virus protein, PS1, exhibits no structural or functional correlation with its native counterpart. PS1 and its ri analog do not exhibit similar conformational propensities. PS1 is less flexible relative to its ri version. These observed structure-function relationships of the ri-peptide epitopes are consistent with the differences in recognition properties between peptide-MHC vs peptide-Ab binding where, while the recognition of the epitope by MHC is pattern based, the exquisitely specific recognition of Ag by Ab arises from the high complementarity between the Ag and the binding site of the Ab. It is evident that the correlation of conformational and interaction propensities of native L-peptides and their ri counterparts depends both on their inherent structural properties and on their mode of recognition.     

Remarkable phylum selectivity of a Schistocerca gregaria trypsin inhibitor: the possible role of enzyme-inhibitor flexibility

A 35-mer polypeptide isolated from the hemolymph of desert locust Schistocerca gregaria (SG) proved to be a canonical inhibitor of bovine trypsin (K(i) = 0.2 microM). Despite having a trypsin-specific arginine at the primary specificity P(1) site, it inhibits bovine chymotrypsin almost as well (K(i) = 2 microM). Furthermore, while the latter reactivity improves 10(4)-fold by the single replacement of P(1) Arg by Leu, changing P(1)' from Lys to Met only moderately improves trypsin affinity (K(i) = 30 nM). The apparent low compatibility to trypsin, however, is not observed vs two arthropodal trypsins: SG peptides with P(1) Arg inhibit crayfish and shrimp trypsins with K(i) values in the picomolar range. This unprecedented high discrimination between orthologous enzymes is postulated to derive from flexibility differences in the protein-protein interaction. The more than four orders of magnitude phylum selectivity makes these peptides prospective candidates for agricultural use.     

A pregnane ester and its glycoside from Orthenthera viminea

A new pregnane ester named ornogenin and its diglycoside designated as ornine were isolated from the dried twigs of Orthenthera viminea. On the basis of chemical and spectroscopic evidence, their structures were established as 12,20-di-O-cinnamoyl-sarcostin and 12,20-di-O-cinnamoyl-sarcostin-3-O-α-L-oleandropyranosyl(1 → 4)-O-β-D-cymaropyranoside, respectively.     

Enhancement of hyperthermia-induced apoptosis by a new synthesized class of furan-fused tetracyclic compounds

The combined effects of hyperthermia (44 degrees C, 20 min) or X-rays (10 Gy) and a new class of furan-fused tetracyclic synthesized compounds (DFs), on apoptosis in human lymphoma U937 cells were investigated. Among the tested compounds (DF1 approximately 6), the combined treatment of 10 microM DF with TIPS (triisopropylsilyloxy) (Designated #3 DF3) and hyperthermia showed the largest potency to induce DNA fragmentation at 6 h after hyperthermia but no enhancement was observed if it was combined with X-rays. Enhancement of hyperthermia-induced apoptosis by DF3 in a dose-dependent manner was observed. When the cells were treated first with DF3 at a nontoxic concentration of 20 microM, and exposed to hyperthermia afterwards, a significant enhancement of heat-induced apoptosis was evidenced by DNA fragmentation, morphological changes and phosphatidylserine externalization. The activation of Bid, but no change of Bax and Bcl-2 were observed after the combined treatment. The release of cytochrome c from mitochondria to cytosol, which was induced by hyperthermia, was enhanced by DF3. Mitochondrial transmembrane potential was decreased and the activation of caspase-3 and caspase-8 was enhanced in the cells treated with the combination. Externalization of Fas was observed following the combined treatment. Flow cytometry revealed rapid and sustained increase of intracellular superoxide due to DF3, and showed subsequent and transient increase in the formation of intracellular hydrogen peroxide (H(2)O(2)), which was further increased when hyperthermia was combined. These results indicate that the intracellular superoxide and H(2)O(2) generated by DF3 enhance the hyperthermia-induced apoptosis via the Fas-mediated mitochondrial caspase-dependent pathway.     

Antibacterial properties of Apis dorsata honey against some bacterial pathogens

Now-a-days, different bioproducts are being used extensively for the welfare of mankind. However, for proper utility of any bioproduct, the exact biotechnological potential of that product should be explored. Honey is produced in almost every country on the planet. It has long been used as a medicinal agent in addition to its broader use as a popular food throughout the human history. It can be used to treat various diseases without causing any negative side effects. In the present study, the antibacterial potential of honey produced by A. dorsata was investigated at its variable concentrations (25, 50, 75 and 100 %) against four pathogenic bacterial species. The highest antimicrobial action was seen against E. coli at 100 % concentration of the honey while showing zone of inhibition of 37.5 ± 3.5 mm. However, the lowest antibacterial action was observed against E. faecalis. The overall order of growth inhibition by the honey at its 100 % concentration for the implicated bacterial species appeared as: E. coli ˃ P. aeruginosa ˃ S. aureus ˃ E. faecalis. The honey couldn’t show antibacterial action at its 25 % concentration. Our findings of the present study will be helpful for utility of the honey as an alternative medicine for curing different complications caused by microbial pathogens.     

Methanolic extract of Citrullus colocynthis suppresses growth and proliferation of breast cancer cells through regulation of cell cycle

Breast cancer is a major cause of cancer related deaths in women worldwide. Available treatments pose serious limitations such as systemic toxicity, metastasis, tumor recurrence, off-target effects, and drug resistance. In recent years, phytochemicals such as secondary metabolites due to their effective anticancer potential at very low concentration have gained attention. Aim of the study was to evaluate anticancer potential of Citrullus colocynthis and its possible molecular targets on MCF-7, a human breast cancer cell line. Methanolic extract of leaves was prepared and fractionated by solvents (n-hexane, chloroform, ethyl acetate and n-butanol) with increasing polarity. Bioassays and gene expression regulation was conducted to evaluate the anticancer activity, proliferation rate and cell cycle regulation of breast cancer cells treated with extract and its fractions, separately. Results showed a significant anticancer activity of methanolic extract of C. colocynthis and two of its fractions prepared with chloroform and ethyl acetate. Bioassays depicted significant decrease in proliferation and growth potential along with cell cycle arrest of treated cells compared to control untreated cells. Expression regulation of genes further confirmed the cell cycle arrest through significant upregulation of cyclin-CDK inhibitors (p21 and p27) and cell cycle checkpoint regulators (HUS1, RAD1, ATM) followed by downregulation of downstream cell cycle progression genes (Cyclin A, Cyclin E, CDK2). It is concluded that C. colocynthis arrests cell cycle in human breast cancer cells through expression regulation of cyclin-CDK inhibitors and with further research can be proposed for therapeutic interventions.     

Microwave-Assisted Organic Synthesis,structure–activity relationship,kinetics and molecular docking studies of non-cytotoxic benzamide derivatives as selective butyrylcholinesterase inhibitors

A series of benzamide derivatives 1–12 with various functional groups (–H, –Br, –F, –OCH₃, –OC₂H₅, and –NO₂) was synthesized using an economic, and facile Microwave-Assisted Organic Synthesis, and evaluated for acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE) activity in vitro. Structure–activity relationship showed that the substitution of –Br group influenced the inhibitory activity against BCHE enzyme. Synthesized compounds were found to be selective inhibitors of BCHE. In addition, all compounds 1–12 were found to be non-cytotoxic, as compared to the standard cycloheximide (IC₅₀ = 0.8 ± 0.2 µM). Among them, compound 3 revealed the most potent BCHE inhibitory activity (IC₅₀ = 0.8 ± 0.6 µM) when compared with the standard galantamine hydrobromide (IC₅₀ = 40.83 ± 0.37 µM). Enzyme kinetic studies indicated that compounds 1, 3–4, and 7–8 showed a mixed mode of inhibition against BCHE, while compounds 2, 5–6 and 9 exhibited an uncompetitive pattern of inhibition. Molecular docking studies further highlighted the interaction of these inhibitors with catalytically important amino acid residues, such as Glu197, Hip438, Phe329, and many others.     

Sustained Delivery of IL-1Ra from PF127-Gel Reduces Hyperglycemia in Diabetic GK-Rats

Interleukin-1beta (IL-1β) is a major cause for induction of various inflammatory mechanisms that are decisively involved to provoke pathogenesis of type 2 diabetes mellitus (T2DM). Interleukin-1 receptor antagonist (IL-1Ra) a naturally occurring anti-inflammatory antagonist of IL-1β has been recently approved for treatment of T2DM but due to its short half-life, higher doses and frequent dosing intervals are required. Pluronic F-127 (PF127) has previously shown to prolong the release of various proteinous drugs and their serum half-lives. Subsequently, in our previous work, we developed a new dosage form of IL-1Ra using PF127 and investigated its in-vitro and in-vivo effects. Here in present work, we have extended this approach using diabetic Goto-kakizaki (GK) rats. We administered IL-1Ra loaded in PF127 gel subcutaneously for one month into GK rats. IL-1Ra loaded in PF127 gel exhibited a sustained and prolonged hypoglycemic effects on treated animals. Intraperitoneal glucose tolerance test (IPGTT) results showed that IL-1Ra loaded in PF127 gel increased glucose tolerance along with increased insulin sensitivity and β-cell’s secretory function in treated rats. Moreover, significant reduction in pro-insulin/insulin ratio, lipid profiles and interleukin 6 (IL-6) were also observed. Immunohistochemical analysis showed slight macrophages infiltration in pancreatic islets. Histochemical analysis revealed no PF127-induced alteration in the normal physiology of skin and kidney of treated animals. Hence, we concluded that IL-1Ra loaded in PF127 gel has potential to exhibit broad spectrum anti-inflammatory effects alleviating the symptoms of T2DM.