Effect of Ocimum tenuiflorum Leaf Extract against Infective Endocarditis

The ever increasing resistance of pathogens to antibiotics as well as the undesirable side effects of certain antimicrobial agents has necessitated the discovery of novel natural products. The ethanolic extract of O. tenuiflorum was investigated against S. aureus isolate which is a major pathogen causing infective endocarditis. The total phenolic content in O. tenuiflorum was found to be 1289 μg gallic acid equivalent/g and HPLC profile revealed the presence of catechin, Caffeic acid and p-coumaric acid. The antibacterial profile of O. tenuiflorum against S. aureus isolate from infective endocarditis patients exhibited significant inhibition at the MIC of 50 μg/ml and the standard antibiotic Vancomycin showed inhibition at 40 ng/ml. Percent inhibition of viable growth was found to be >95% and the scanning electron micrographs (SEM) revealed the disruption of the membrane of S. aureus treated with O. tenuiflorum extract. The antimicrobial activity correlates with phenolic content of the extract. These results demonstrate the potency of O. tenuiflorum, could serve as a new source of antimicrobials with potential applications and related health benefits

PHYTO-ANTIQUORUMONES: AN HERBAL APPROACH FOR BLOCKING BACTERIAL TRAFFICKING AND PATHOGENESIS

Over centuries, plants are the richest resource of curative drugs as cited in folklore, traditional and modern medicinal systems and are been used as nutraceuticals, functional food supplements and in pharmaceuticals. Phytochemicals have exhibited beneficial effects against human acute and chronic ailments caused due to microbial pathogens. In recent years, phytochemicals and their derivatives have been extensively used as potent antimicrobials in humans and livestock due to their chemical stability, high bioavailability, low-molecular mass, safe consumption without any side-effect as seen in many antibiotic regimes. These phytocompounds have also been highlighted to function as Quorum Sensing Inhibitors (QSI) or antiquorumones in blocking bacterial pathogenesis preventing their regulatory mechanism and expression of specific set of virulence genes or cascades. However, the role of phytochemicals as QSI has been poorly identified but many of which remain unexplored. Therefore, this review summarizes most of the current scientific contributions focused on the use of plant phytochemicals as antiquorumones, highlighting the significance of plant derived molecules as bacterial inhibitors with larger emphasis on the mechanistic action of biofilm formation and quorum signaling networks mainly N-acylhomoserine lactones (AHLs), autoinducer-2 (AI-2) communications and their attributes in modulating the host immune response. A critical understanding of this complex trio-interaction between humans, microbes and phytochemicals has to be well explored, to exploit the usefulness of these metabolites ultimately paving newer paths for herbal drug discovery and their potential targets leading towards a better quality of life and human welfare.Â

Point Mutations in Aβ Result in the Formation of Distinct Polymorphic Aggregates in the Presence of Lipid Bilayers

A hallmark of Alzheimer's disease (AD) is the rearrangement of the β-amyloid (Aβ) peptide to a non-native conformation that promotes the formation of toxic, nanoscale aggregates. Recent studies have pointed to the role of sample preparation in creating polymorphic fibrillar species. One of many potential pathways for Aβ toxicity may be modulation of lipid membrane function on cellular surfaces. There are several mutations clustered around the central hydrophobic core of Aβ near the α-secretase cleavage site (E22G Arctic mutation, E22K Italian mutation, D23N Iowa mutation, and A21G Flemish mutation). These point mutations are associated with hereditary diseases ranging from almost pure cerebral amyloid angiopathy (CAA) to typical Alzheimer's disease pathology with plaques and tangles. We investigated how these point mutations alter Aβ aggregation in the presence of supported lipid membranes comprised of total brain lipid extract. Brain lipid extract bilayers were used as a physiologically relevant model of a neuronal cell surface. Intact lipid bilayers were exposed to predominantly monomeric preparations of Wild Type or different mutant forms of Aβ, and atomic force microscopy was used to monitor aggregate formation and morphology as well as bilayer integrity over a 12 hour period. The goal of this study was to determine how point mutations in Aβ, which alter peptide charge and hydrophobic character, influence interactions between Aβ and the lipid surface. While fibril morphology did not appear to be significantly altered when mutants were prepped similarly and incubated under free solution conditions, aggregation in the lipid membranes resulted in a variety of polymorphic aggregates in a mutation dependent manner. The mutant peptides also had a variable ability to disrupt bilayer integrity

Chronic Intranasal Treatment with an Anti-Aβ30-42 scFv Antibody Ameliorates Amyloid Pathology in a Transgenic Mouse Model of Alzheimer's Disease

Amyloid-beta peptide (Aβ)-directed active and passive immunization therapeutic strategies reduce brain levels of Aβ, decrease the severity of beta-amyloid plaque pathology and reverse cognitive deficits in mouse models of Alzheimer's disease (AD). As an alternative approach to passive immunization with full IgG molecules, single-chain variable fragment (scFv) antibodies can modulate or neutralize Aβ-related neurotoxicity and inhibit its aggregation in vitro. In this study, we characterized a scFv derived from a full IgG antibody raised against the C-terminus of Aβ, and studied its passage into the brains of APP transgenic mice, as well as its potential to reduce Aβ-related pathology. We found that the scFv entered the brain after intranasal application, and that it bound to beta-amyloid plaques in the cortex and hippocampus of APP transgenic mice. Moreover, the scFv inhibited Aβ fibril formation and Aβ-mediated neurotoxicity in vitro. In a preventative therapeutic approach chronic intranasal treatment with scFv reduced congophilic amyloid angiopathy (CAA) and beta-amyloid plaque numbers in the cortex of APPswe/PS1dE9 mice. This reduction of CAA and plaque pathology was associated with a redistribution of brain Aβ from the insoluble fraction to the soluble peptide pool. Due to their lack of the effector domain of full IgG, scFv may represent an alternative tool for the treatment of Aβ-related pathology without triggering Fc-mediated effector functions. Additionally, our observations support the possibility that Aβ-directed immunotherapy can reduce Aβ deposition in brain vessels in transgenic mice

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches

Transcriptional analysis of Thiol Disulfide Redox Metabolism (TDRM) genes in Listeria monocytogenes in biofilm and planktonic forms grown at different temperatures

Listeria monocytogenes is a food-borne pathogen, which tolerates a wide range of stress conditions. The organism being robust, its stress adaptation strategies are poorly understood. The thiol disulfide redox metabolic pathway plays a pivotal role in combating the stress response induced during growth environments, especially in biofilms wherein the bacterium gains the ability to withstand various environmental stress factors. So far the effect of different temperatures on genes involved in thiol disulfide redox metabolism (TDRM) in relation to biofilm and planktonic cells has not yet been studied in L. monocytogenes. This study aims to understand the involvement of specific TDRM genes encoding for thioredoxin, glutathione, peroxide and their transcriptional regulator systems using Real-Time PCR (Qrt-PCR) for planktonic and biofilm cells grown at different temperature of 18 0 C, 25 0C, 30 0C and 37 0C. The results obtained suggest that TDRM genes analyzed were highly regulated in mature biofilms than their planktonic counterpart at 30 0C. Furthermore, rpoB, a RNA polymerase beta-subunit, was standardized as internal control for optimization of qRT-PCR. The transcriptome analysis could explain the thiol disulfide redox metabolism in combating stress, which contributes to bacterial survival in food processing environments and host-pathogen interactions

Evaluation of antibiotic susceptibility in mixed culture biofilms

Antibiotic therapy against an established biofilm often fails without removal of the infected implant, despite the use of drugs which are highly active in standard in vitro susceptibility tests. In contrast to antibiotic therapy of many bacterial infections, standard in vitro susceptibility tests are not predictive of the therapeutic outcome. To study this complex phenomenon we developed a simple cellulose dialysis membrane model system to evaluate the penetration of antimicrobial agent namely vancomycin on mixed culture biofilm formed by Staphylococcus epidermidis RP62A and Listeria monocytogenes EDG-e. Biofilm formation was optimized at 30 C on cellulose membrane with tryptic soy broth (TSB) supplemented with 1% glucose and 0.6% yeast extract as the culture medium and cultivation duration of 48 h so as to mimic an infected biomaterial or food processing environment. Biofilm development on the membranes was confirmed by scanning election microscopy and penetration of antibacterial agent was demonstrated by a simple diffusion cell bioassay of antibiotic-affected cells of the biofilm. The results showed that planktonic mixed culture bacteria was rapidly killed by treatment with 0.1 ml of vancomycin and in contrast, failed to effectively kill the bacteria in mixed biofilms. Acquisition of resistance to antibiotics would represent a major therapeutic problem. Thus it is very important to test for antibiotic resistance in food-borne and clinical isolates and to reconsider critically the use of antibiotics

INHIBITION OF MULTI-TOXIC PHOSPHOLIPASE A2 OF DABOII RUSELLII PULCHELLA VENOM BY THE ETHANOLIC EXTRACT OF A. PANICULATA

Objective: Andrographis paniculata (A. paniculata) Nees is an important medicinal plant found in the tropical regions and has been traditionally used in Indian and Chinese medicinal systems. A. paniculata is found to exhibit anti-snake venom properties; however its inhibitory potential on multi-toxic Phospholipases A2 and its associated inflammatory reactions is not clearly understood. Henceforth, in this study we evaluate the inhibitory/neutralizing potential of alcoholic extract of A. paniculata on the isolated multi-toxic PLA2 (of Daboii rusellii pulchella and Naja naja) and its induced edema in Swiss albino mice.Methods: The multi-toxic-svPLA2-VRV-PL-V from the venom of Daboii rusellii pulchella was purified according established methods. The inhibition of enzymatic activity and edema inducing activity was carried out according to established methods.Results: A. paniculata extract dose dependently inhibited the multi-toxic svPLA2 enzymaticactivity with an IC50 value of 12.4±0.6 µg/ml. Further, the extract dose dependently inhibited the edema formation, when co-injected with the enzyme indicating a strong correlation between lipolytic activity and pro-inflammatory activity.Conclusion: The ethanolic extract of A. paniculata effectively inhibited the multi-toxic svPLA2 and its associated edema inducing activities, which substantiate their anti-ophidian properties. Further study is interesting to develop them into potent anti-ophidian agents.Â

Anti-venom potential of aqueous extract of stem bark of Mangifera indica L. against Daboia russellii (Russell's viper) venom

Several plant extracts rich in pharmacologically active compounds have shown to antagonize venom of several species. Mangifera indica has been used against snakebite by the traditional healers, However, there is paucity of scientific data in support. In this study, we evaluated the antivenom potential of aqueous extract of stem bark of M. indica against D. russellii venom-induced pharmacological effects such as life myotoxicity, edema, LD50 etc. The extract inhibited the phospholipase, protease, hyaluronidase, 5'nucleotidase, ATPase and alkaline phosphomonoesterase activities with varying IC50 values. It significantly inhibited both metalloproteases and serine proteases activities. Further, the extract significantly reduced the myotoxicity of the venom, as evident by the reduction of serum creatin kinase and lactate dehydrogenase activities. Though the extract completely inhibited in vitro PLA(2) activity, it was unable to completely inhibit in situ hemolytic and in vivo edema-inducing activities, usually brought about by PLA(2)s. In lethality studies, co-injection of the venom preincubated with the extract showed higher protection than the independent injection of venom, followed by the extract in the mice. However, in both the cases the extract -a cocktail of inhibitors significantly increased the survival time, when compared to that of mice injected (i.p) with the venom alone. These results encourage further studies on the potential use of cocktail of inhibitors in improving the treatment of snake envenomation. Further, this study substantiates the use of M. indica as an antidote against snakebite by the traditional healers

Interaction of Listeria monocytogenesandstaphylococcus epidermidisin dual species biofilms

The development of mixed biofilms ofListeria monocytogenesandSta-phylococcus epidermidiswas studied on two model surfaces. Growth tests at30C for mono and mixed cultures of the two bacteria in defined Hsiang-NingTsai Medium, in tryptic soy broth (TSB)+1% glucose, TSB+0.6% yeastextract (TSBYE) and TSBYE+1% glucose was performed. The optimalgrowth was seen in TSBYE+1% glucose, and hence, biofilm formation in thismedium was studied using a polystyrene microtiter plate assay. Mono andmixed cultures with different ratios of the two bacteria were assayed for (1)biofilm strength, expressed as the amount of cell-bound crystal violet and (2)amount of matrix polysaccharide measured by ruthenium red staining. Themixture with a 40:60 ratio ofL. monocytogenestoS. epidermidisyielded thehighest values in both assays. The biofilm strength measured for this ratioindicated a synergistic interaction between the two bacterial species. Scan-ning electron microscopy of biofilms formed on cellulose membranes alsorevealed such an interaction