GRP78 regulates sensitivity of human colorectal cancer cells to DNA targeting agents

This study was carried out to investigate the activation status of unfolded protein response (UPR) in colorectal cancer (CRC) and its contribution to CRC resistance to chemotherapy-induced apoptosis. Chemotherapy-induced apoptosis was assessed by the propidium iodide method. Activation of UPR was evaluated in CRC cell lines using immunoblotting technique and in CRC tissues using immunohistochemistry. Findings of the present study revealed that the UPR is constitutively activated in CRC cell lines and CRC tissues isolated from patients, as evidenced by relatively high levels of the 78-kDa glucose-regulated protein (GRP78) and spliced X-box-binding protein 1 mRNA in tissue samples. In addition, CRC cell lines differentially responded to clinically relevant DNA-targeting agents including cisplatin, and 5-flourouracil. Moreover, the levels of GRP78 were inversely associated with sensitivity of CRC cells to chemotherapy-induced apoptosis. Inhibition of GRP78 by siRNA resulted in increased sensitivity of CRC cells to chemotherapeutic agents. Collectively, current results appear to provide novel insights into the role of UPR in determining sensitivity of CRC cells to chemotherapeutic agents and might have important implications for personalized CRC treatment.     

In Vitro Synergistic Activities of the Hybrid Antimicrobial Peptide MelitAP-27 in Combination with Conventional Antibiotics Against Planktonic and Biofilm Forming Bacteria

The extensive use of antibiotics for the treatment of human infections during the last few decades has led to a dramatic increase in the emergence of multidrug-resistant bacteria (MDRB) among various bacterial strains. Global research is currently focused on finding novel alternative agents with different mechanisms of action rather than the use of conventional antibiotics to counteract the threat of bacterial and biofilm infections. Antimicrobial peptides represent promising alternative agents for conventional antibiotics as these molecules display a broad spectrum of activity against several microorganisms. Recently, we have designed a novel hybrid antimicrobial peptide named MelitAP-27. This peptide has been found to display potent broad spectrum and selective in vitro antimicrobial activities against a wide range of Gram-positive and Gram-negative bacteria. In the present study, the in vitro antimicrobial and antibiofilm activities of the peptide alone and in combination with five different types of antibiotics were assessed against wild-type and resistant Gram-positive and Gram-negative bacterial strains. Our results showed that most of the combination groups displayed a synergistic mode of action against planktonic and biofilm forming bacteria which resulted in decreasing the effective MIC values for MelitAP-27 to the nanomolar concentrations. These effective concentrations were associated with negligible toxicities on mammalian cells. The results of our study indicate that combinations of MelitAP-27 with conventional antibiotics may be pursued as a potential novel treatment strategy against MDRB and biofilm forming bacteria.     

Identification of 2-Aminothiazole-4-Carboxylate Derivatives Active against Mycobacterium tuberculosis H37Rv and the β-Ketoacyl-ACP Synthase mtFabH

Background

Tuberculosis (TB) is a disease which kills two million people every year and infects approximately over one-third of the world''s population. The difficulty in managing tuberculosis is the prolonged treatment duration, the emergence of drug resistance and co-infection with HIV/AIDS. Tuberculosis control requires new drugs that act at novel drug targets to help combat resistant forms of Mycobacterium tuberculosis and reduce treatment duration.

Methodology/Principal Findings

Our approach was to modify the naturally occurring and synthetically challenging antibiotic thiolactomycin (TLM) to the more tractable 2-aminothiazole-4-carboxylate scaffold to generate compounds that mimic TLM''s novel mode of action. We report here the identification of a series of compounds possessing excellent activity against M. tuberculosis H₃₇R_v and, dissociatively, against the β-ketoacyl synthase enzyme mtFabH which is targeted by TLM. Specifically, methyl 2-amino-5-benzylthiazole-4-carboxylate was found to inhibit M. tuberculosis H₃₇R_v with an MIC of 0.06 µg/ml (240 nM), but showed no activity against mtFabH, whereas methyl 2-(2-bromoacetamido)-5-(3-chlorophenyl)thiazole-4-carboxylate inhibited mtFabH with an IC₅₀ of 0.95±0.05 µg/ml (2.43±0.13 µM) but was not active against the whole cell organism.

Conclusions/Significance

These findings clearly identify the 2-aminothiazole-4-carboxylate scaffold as a promising new template towards the discovery of a new class of anti-tubercular agents.     

Antimicrobial and Antibiofilm Activity of Mauriporin,a Multifunctional Scorpion Venom Peptide

Many pathogenic free living and biofilm forming bacterial organisms can cause serious infections to humans that could consequently have devastating effects on human health. A significant number of these microbial organisms are resistant to almost all known conventional antibiotics and the ability of some these strains to form sessile communities of biofilms increases the resistance ability of bacteria to antibiotic treatment. Global research is currently focused on finding novel therapies to counteract the threat of bacterial and biofilm infections rather than using conventional antibiotics. Mauriporin, a novel cationic α-helical peptide identified from the venom derived cDNA library of the scorpion Androctonus mauritanicus was reported to display selective cytotoxic and anti-proliferative activity against prostate cancer cell lines. In the present study, we investigated the antimicrobial and antibiofilm activities of Mauriporin. Our results show that Mauriporin displays potent antimicrobial activities against a range of Gram-positive and Gram-negative planktonic bacteria with MIC values in the range 5 µM to 10 µM. Mauriporin was also able to prevent Pseudomonas aeruginosa biofilm formation while showing weak hemolytic activity towards human erythrocytes. Studies on the mechanism of action of Mauriporin revealed that the peptide is probably inducing bacterial cell death through membrane permeabilization determined by the release of β-galactosidase enzyme from peptide treated Escherichia coli cells. Moreover, DNA binding studies found that Mauriporin can cause potent binding to intracellular DNA. All these results indicate that Mauriporin has a considerable potential for therapeutic application as a novel drug candidate for eradicating bacterial infections.     

Mauriporin, a Novel Cationic α-Helical Peptide with Selective Cytotoxic Activity Against Prostate Cancer Cell Lines from the Venom of the Scorpion Androctonus mauritanicus

Prostate cancer is the second most common cancer in men and the second leading cause of cancer-related deaths among men in the western world. Finding a cure for prostate cancer is urgently needed. Scorpion venoms are rich sources of biologically active peptides, among which the non-disulfide bridged peptides constitute an important group displaying multifunctional activities. The non-disulfide bridged scorpion venom peptides are rarely identified and poorly characterized so far. In this work, we report the molecular cloning and functional characterization of a novel non-disulfide bridged peptide from the venomous gland cDNA library of the Moroccan scorpion Androctonus mauritanicus. Named Mauriporin, the peptide was found to be composed of 48 residues and circular dichroism analysis revealed the peptide to display a well defined α-helical structure in membrane mimicking environments. A synthetic replicate of Mauriporin was found to exert potent selective cytotoxic and antiproliferative activity against prostate cancer cell lines (IC₅₀ 4.4–7.8 μM) when compared with non-tumorigenic cells. In this concentration range, Mauriporin produced also negligible degrees of hemolytic activities against mammalian erythrocytes. Apoptotic studies displayed that Mauriporin is not causing cell death through an apoptotic-mediated pathway but possibly through a necrotic mode of cell death. In conclusion Mauriporin may offer a novel therapeutic strategy in the treatment of prostate cancer considering its significant cytotoxic potency against prostate cancer cells and low toxicity to non-tumorigenic cells.