M. Obayed Ullah

Hydroxycinnamic acid derivatives: A potential class of natural compounds for the management of lipid metabolism and obesity

Hydroxycinnamic acid derivatives are important class of polyphenolic compounds originated from the Mavolanate-Shikimate biosynthesis pathways in plants. Several simple phenolic compounds such as cinnamic acid, p-coumaric acid, ferulic acid, caffeic acid, chlorgenic acid, and rosmarinic acid belong to this class. These phenolic compounds possess potent antioxidant and anti-inflammatory properties. These compounds were also showed potential therapeutic benefit in experimental diabetes and hyperlipidemia. Recent evidences also suggest that they may serve as valuable molecule for the treatment of obesity related health complications. In adipose tissues, hydroxycinnamic acid derivatives inhibit macrophage infiltration and nuclear factor κB (NF-κB) activation in obese animals. Hydroxycinnamic acid derivatives also reduce the expression of the potent proinflammatory adipokines tumor necrosis factor-α (TNFα), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor type-1 (PAI-1), and they increase the secretion of an anti-inflammatory agent adiponectin from adipocytes. Furthermore, hydroxycinnamic acid derivatives also prevent adipocyte differentiation and lower lipid profile in experimental animals. Through these diverse mechanisms hydroxycinnamic acid derivatives reduce obesity and curtail associated adverse health complications.

TRIF-dependent TLR signaling, its functions in host defense and inflammation, and its potential as a therapeutic target

Toll/IL‐1R domain‐containing adaptor‐inducing IFN‐β (TRIF)‐dependent signaling is required for TLR‐mediated production of type‐I IFN and several other proinflammatory mediators. Various pathogens target the signaling molecules and transcriptional regulators acting in the TRIF pathway, thus demonstrating the importance of this pathway in host defense. Indeed, the TRIF pathway contributes to control of both viral and bacterial pathogens through promotion of inflammatory mediators and activation of antimicrobial responses. TRIF signaling also has both protective and pathologic roles in several chronic inflammatory disease conditions, as well as an essential function in wound‐repair processes. Here, we review our current understanding of the regulatory mechanisms that control TRIF‐dependent TLR signaling, the role of the TRIF pathway in different infectious and noninfectious pathologic states, and the potential for manipulating TRIF‐dependent TLR signaling for therapeutic benefit.

The TLR signalling adaptor TRIF/TICAM-1 has an N-terminal helical domain with structural similarity to IFIT proteins

TRIF/TICAM-1 (TIR domain-containing adaptor inducing interferon-β/TIR domain-containing adaptor molecule 1) is the adaptor protein in the Toll-like receptor (TLR) 3 and 4 signalling pathway that leads to the production of type 1 interferons and cytokines. The signalling involves TIR (Toll/interleukin-1 receptor) domain-dependent TRIF oligomerization. A protease-resistant N-terminal region is believed to be involved in self-regulation of TRIF by interacting with its TIR domain. Here, the structural and functional characterization of the N-terminal domain of TRIF (TRIF-NTD) comprising residues 1-153 is reported. The 2.22 Å resolution crystal structure was solved by single-wavelength anomalous diffraction (SAD) using selenomethionine-labelled crystals of TRIF-NTD containing two additional introduced Met residues (TRIF-NTDA66M/L113M). The structure consists of eight antiparallel helices that can be divided into two subdomains, and the overall fold shares similarity to the interferon-induced protein with tetratricopeptide repeats (IFIT) family of proteins, which are involved in both the recognition of viral RNA and modulation of innate immune signalling. Analysis of TRIF-NTD surface features and the mapping of sequence conservation onto the structure suggest several possible binding sites involved in either TRIF auto-regulation or interaction with other signalling molecules or ligands. TRIF-NTD suppresses TRIF-mediated activation of the interferon-β promoter, as well as NF-κB-dependent reporter-gene activity. These findings thus identify opportunities for the selective targeting of TLR3- and TLR4-mediated inflammation.

In vitro studies on antibacterial, antifungal,and cytotoxic properties of Leucas aspera

The leaves of the plant Leucas aspera belonging to the family Lamiaceae was studied to determine the in vitro antibacterial, antifungal, and cytotoxic properties. All extracts showed remarkable antibacterial activity against all of the studied organisms except Escherichia coli. Methanol extract showed stronger activity compared to ethyl acetate and petroleum ether extracts. It showed highest activity against Pseudomonas aeruginosa with zone of inhibition of 15 mm. The standard chloramphenicol did not show any activity against Shigella sonnei. But all the extracts showed moderate activity against this pathogen with zone of inhibition ranging from 10 to 13 mm. None of the extracts has shown any significant antifungal activity against the fungi. Incase of brine shrimp lethality bioassay, methanol extract showed the strongest cytotoxic effect with LC50 value of 4.28 μg/ml which is followed by ethyl acetate extract with LC50 value of 5.36 μg/ml. Thus it can be inferred that this plant may be a potential source of novel bioactive compounds.

Effect of Rohitakarista (RHT), an ayurvedic formulation, on the lipid profile of rat plasma after chronic administration

Rohitakarista (RHT), a popular Ayurvedic formulation, is the preparation of Tecomella undulate with other medicinal plants. In this study, the lipid profile of rats’ plasma was studied after chronic administration of RHT usually used in the disease of spleen, abdomen and localized abdominal swelling or tumor. The animal was albino rats (Rattus novergicus: Sprague-Dawley strains) and RHT was administered per oral route at a dose of 100mg/kg body weight, once daily, up to 46 days for all the experiments. Forty rats, equally of both sexes, were randomly grouped into four where one male and one female group were used as control and other groups were used as test. In both of the male and female rats there was a statistically very high significant decrease in the Triglycerides (p=0.001***). On the contrary, a statistically very highly significant increase in the total cholesterol (p=0.001***), VLDL (p=0.001***) and HDL (p=0.001***) was noted. Similar results were observed in case of female rats. Also the increase in LDL (p=0.028*) was statistically significant for both of the sexes of RHT treated rats.

Crystallization and X-ray diffraction analysis of the N-terminal domain of the Toll-like receptor signalling adaptor protein TRIF/TICAM-1

As part of the mammalian innate immune response, Toll-like receptors 3 and 4 can signal via the adaptor protein TRIF/TICAM-1 to elicit the production of type-I interferons and cytokines. Recent studies have suggested an auto-inhibitory role for the N-terminal domain (NTD) of TRIF. This domain has no significant sequence similarity to proteins of known structure. In this paper, the crystallization and X-ray diffraction analysis of TRIF-NTD and its selenomethionine-labelled mutant TRIF-NTD(A66M/L113M) are reported. Thin plate-like crystals of native TRIF-NTD obtained using polyethylene glycol 3350 as precipitant diffracted X-rays to 1.9 Å resolution. To facilitate phase determination, two additional methionines were incorporated into the protein at positions chosen based on the occurrence of methionines in TRIF homologues in different species. Crystals of the selenomethionine-labelled protein were obtained under conditions similar to the wild-type protein; these crystals diffracted X-rays to 2.5 Å resolution. The TRIF-NTD and TRIF-NTD(A66M/L113M) crystals have the symmetry of space groups P212121 and P1, and most likely contain two and four molecules in the asymmetric unit, respectively. These results provide a sound foundation for the future structure determination of this novel domain.

Cloning, expression, purification, crystallization and preliminary X-ray crystallographic analysis of the TIR domain from the Brucella melitensis TIR-domain-containing protein TcpB

In mammals, Toll-like receptors (TLRs) recognize conserved microbial molecular signatures and induce an early innate immune response in the host. TLR signalling is mediated by interactions between the cytosolic TIR (Toll/interleukin-1 receptor) domains of the receptor and the adaptor proteins. Increasingly, it is apparent that pathogens target this interaction via pathogen-expressed TIR-domain-containing proteins to modulate immune responses. A TIR-domain-containing protein TcpB has been reported in the pathogenic bacterium Brucella melitensis. Studies have shown that TcpB interferes with the TLR2 and TLR4 signalling pathways to inhibit TLR-mediated inflammatory responses. Such interference may involve TIR-TIR-domain interactions between bacterial and mammalian proteins, but there is a lack of information about these interactions at the molecular level. In this study, the cloning, expression, purification, crystallization and preliminary X-ray crystallographic analysis of the protein construct corresponding to the TIR domain of TcpB (residues 120-250) are reported. The crystals diffracted to 2.6 Å resolution, have the symmetry of the monoclinic space group P2₁ and are most likely to contain four molecules in the asymmetric unit. The structure should help in understanding the molecular basis of how TcpB affects the innate immunity of the host.

Molecular docking and dynamics of Nickel-Schiff base complexes for inhibiting β-lactamase of Mycobacterium tuberculosis

In recent years, multidrug-resistance has become a primary concern in the treatment and management of tuberculosis, an infectious disease caused by Mycobacterium tuberculosis. In this context, searching new anti-tuberculosis agents particularly targeting the β-lactamase (BlaC) is reported to be promising as this enzyme is one of the key player in the development of multidrug resistance. This study reports the design of some Nickel (Ni) based tetradentate N2O2 Schiff bases, employing density functional theory. All analogs are optimized at B3LYP/SDD level of theory. Dipole moment, electronic energy, enthalpy, Gibbs free energy, HOMO–LUMO gap, and softness of these modified drugs are also investigated. Molecular interactions between designed ligands and BlaC have been analyzed by molecular docking approach, followed by molecular dynamics (MD) simulation. All designed compounds show low HOMO–LUMO gap, while addition of halogen increases the dipole moment of the compounds. Docking and MD simulation investigations reveal that the designed compounds are more potent than standard inhibitor, where Ile117, Pro290, Arg236 and Thr253 residues of BlaC are found to play important role in the ligand binding. Through MD simulation study, the best binding compound is also observed to form stable complex by increasing the protein rigidness. The ADME/T analysis suggests that modified drugs are less toxic and shows an improved pharmacokinetic properties than that of the standard drug. These results further confirm the ability of Ni-directed Schiff bases to bind simultaneously to the active site of BlaC and support them as potential candidates for the future treatment of tuberculosis disease.

Microbial and Heavy Metal Contaminant of Antidiabetic Herbal Preparations Formulated in Bangladesh

The aim of the current study was to evaluate microbial contamination in terms of microbial load (total aerobic count and total coliform count) and specific pathogenic bacteria (Salmonella spp., Escherichia coli, particularly Escherichia coli 0157) in thirteen antidiabetic herbal preparations (ADHPs) from Dhaka City. All the thirteen ADHPs had been found contaminated with fungi and different pathogenic bacteria. From the data, it is found that only two of these preparations (ADHP-1 and ADHP-12) complied with the safety limit (as stated in different Pharmacopoeias and WHO guidelines) evaluated by all different microbial counts. None of these herbal preparations could assure the safety as all of them were contaminated by fungi. The overall safety regarding heavy metal content (Zn, Cu, Mn, Cr, Cd, and Pb) was assured as none of them exceeded the safety limit of the daily intake. Microbial contaminants in these herbal preparations pose a potential risk for human health and care should be taken in every step involved in the preparation of these herbal preparations to assure safety.