Biomedical subjects

Vivek Malhotra

Publications and source records attributed to Vivek Malhotra.

28 records · Page 2Linked to original sources

PubMed2002

Fragmentation and dispersal of the pericentriolar Golgi complex is required for entry into mitosis in mammalian cells.

The pericentriolar Golgi stacks are fragmented and found dispersed in mitotic mammalian cells. Addition of an antibody to the Golgi-associated protein GRASP65 inhibited Golgi fragmentation by mitotic cytosol in permeabilized cells. Microinjecting this antibody or the C-terminal fragment of GRASP65, which contains the antibody binding site, into normal rat kidney cells prevented entry into mitosis. Under these conditions the cells had completed S phase but were not in the prophase stage of mitosis. Fragmentation of the Golgi apparatus by nocodazole or Brefeldin A treatment prior to or post microinjection of the anti-GRASP65 antibody alleviated the block in mitotic entry. Based on our findings, we suggest that the pericentriolar Golgi organization is a sensor for controlling entry into mitosis in mammalian cells.

Amino Acid Sequence↗

PubMed2002

Heat shock inhibits activation of NF-kappaB in the absence of heat shock factor-1.

The heat shock response is known to inhibit NF-kappaB activation and NF-kappaB-dependent gene expression. Herein we determined if cells lacking heat shock factor-1 (HSF-1), the major transcription factor regulating heat shock protein gene expression, have an altered ability to modulate NF-kappaB activation. Embryonic fibroblasts from HSF-1-null mutant mice (HSF-1-/- cells) had a drastically reduced ability to express heat shock protein-70 in response to heat shock, compared to embryonic fibroblasts from wild-type mice (HSF+/+ cells). There was no difference, however, in the ability of heat shock to inhibit TNFalpha-mediated NF-kappaB activation, IkappaBalpha degradation, IkappaB kinase activation, and macrophage chemotactic protein-1 expression in the HSF-1-/- cells compared to the HSF-1+/+ cells. These data demonstrate that heat shock inhibits activation of the NF-kappaB/IkappaBalpha pathway and NF-kappaB-dependent gene expression in the absence of an intact heat shock response.

Animals↗

PubMed2002

Protein kinase D: an intracellular traffic regulator on the move.

Recent research has identified protein kinase D (PKD, also called PKCmu) as a serine/threonine kinase with potentially important roles in growth factor signaling as well as in stress-induced signaling. Moreover, PKD has emerged as an important regulator of plasma membrane enzymes and receptors, in some cases mediating cross-talk between different signaling systems. The recent discovery of two additional kinases belonging to the PKD family and the plethora of proteins that interact with PKD point to a multifaceted regulation and a multifunctional role for these enzymes, with functions in processes as diverse as cell proliferation, apoptosis, immune cell regulation, tumor cell invasion and regulation of Golgi vesicle fission.

Animals↗

PubMed2002

A green tea-derived polyphenol, epigallocatechin-3-gallate, inhibits IkappaB kinase activation and IL-8 gene expression in respiratory epithelium.

Interleukin-8 (IL-8) is a principle neutrophil chemoattractant and activator in humans. There is interest in developing novel pharmacological inhibitors of IL-8 gene expression as a means for modulating inflammation in disease states such as acute lung injury. Herein we determined the effects of epigallocatechin-3-gallate (EGCG), a green tea-derived polyphenol, on tumor necrosis factor-alpha (TNF-alpha)-mediated expression of the IL-8 gene in A549 cells. EGCG inhibited TNF-alpha-mediated IL-8 gene expression in a dose response manner, as measured by ELISA and Northern blot analysis. This effect appears to primarily involve inhibition of IL-8 transcription because EGCG inhibited TNF-alpha-mediated activation of the IL-8 promoter in cells transiently transfected with an IL-8 promoter-luciferase reporter plasmid. In addition, EGCG inhibited TNF-alpha-mediated activation of IkappaB kinase and subsequent activation of the IkappaB alpha/NF-kappaB pathway. We conclude that EGCG is a potent inhibitor of IL-8 gene expression in vitro. The proximal mechanism of this effect involves, in part, inhibition of IkappaB kinase activation.

Antioxidants↗

PubMed2002

Frequency of patch-test positivity in patients with psoriasis: a prospective controlled study.

Current information on the incidence of patch-test positivity and the spectrum of allergens in psoriatics is conflicting. We compared the rates of patch-test positivity to common allergens and topical medicaments in 200 patients suffering from chronic plaque psoriasis (group I) with 51 patients with other non-allergic skin complaints (group II) and 54 patients suspected of having allergic contact dermatitis (group III). Positive patch-test results to one or more allergens were detected in 21.6% of patients in group I, 23.5% in group II and 50.0% in group III. Psoriatics with > or = 5 years old disease had a higher rate of patch-test positivity than those with shorter disease duration (p<0.01). The site of lesions showed no correlation with patch-test positivity. The commonest allergens showing positivity in group I were dithranol (6.5%), nickel (6%), fragrance mix (5%), neomycin (2%) and nitrofurazone (2%). In spite of the comparable rates of patch-test positivity in psoriatics and general dermatology outpatients, the predominance of sensitivity to topical medicaments and fragrance in the former group was striking. A separate psoriasis series focusing on topical agents may give more accurate information on this subject.

Adult↗

PubMed2002

Ablation of the heat shock factor-1 increases susceptibility to hyperoxia-mediated cellular injury.

High concentrations of oxygen (hyperoxia) are known to cause cellular injury and death. The heat shock response is a highly conserved cellular defense mechanism that protects cells against various environmental stressors, including hyperoxia. Herein we determined the role of heat shock factor-1 (HSF-1), a major component of the heat shock response, in protecting cells against hyperoxia. Embryonic fibroblasts from HSF-1-null mutant mice (HSF-1 -/- cells) were compared to wild-type embryonic fibroblasts (HSF-1 +/+ cells) following 24 hours' exposure to room air or hyperoxia (95% O(2)). Acute survival in hyperoxia was decreased in HSF-1 -/- cells as compared to HSF-1 +/+ cells. Intracellular ATP levels were significantly lower in the HSF-1 -/- cells as compared to the HSF-1 +/+ cells exposed to hyperoxia. Isoprostane levels, a marker of membrane lipid peroxidation, were significantly higher in the HSF-1 -/- cells as compared to the HSF-1 +/+ cells exposed to hyperoxia. Restoration of HSF-1 in the HSF-1 -/- cells by stable transfection with a HSF-1 expression plasmid improved survival in hyperoxia when compared to HSF-1 -/- cells stably transfected with the empty expression vector. Hyperoxia increased activation of HSF-1 in HSF-1 +/+ cells and in HSF-1 -/- cells stably transfected with the HSF-1 expression plasmid. These data demonstrate that HSF-1 plays an important role in conferring resistance to hyperoxia in vitro.

Adenosine Triphosphate↗

PubMed2002

Parthenolide, an inhibitor of the nuclear factor-kappaB pathway, ameliorates cardiovascular derangement and outcome in endotoxic shock in rodents.

Parthenolide is a sesquiterpene lactone used in folk medicine for its anti-inflammatory activity. Recent in vitro studies have shown that this compound inhibits the nuclear factor (NF)-kappaB pathway. This study examines the effect of parthenolide in endotoxic shock in rodents. Endotoxic shock was induced by administration of Escherichia coli endotoxin in rats. Three groups of rats received parthenolide (0.25, 0.5, or 1 mg/kg) 15 min before endotoxin; another group received parthenolide (1 mg/kg) 3 h after endotoxin. In vehicle-treated rats, administration of endotoxin caused severe hypotension, which was associated with a marked hyporeactivity to norepinephrine in ex vivo thoracic aortas. Immunohistochemistry showed positive staining for nitrotyrosine, poly(ADP-ribose) synthetase (PARS) and apoptosis, whereas Northern blot analysis showed increased mRNA expression of inducible nitric-oxide synthase (iNOS) in thoracic aortas. Elevated levels of plasma nitrate/nitrite were also found. Elevated lung levels of myeloperoxidase activity were indicative of infiltration of neutrophils. These inflammatory events were preceded by cytosolic degradation of inhibitor kappaBalpha (IkappaBalpha) and activation of nuclear NF-kappaB in the lung. In vivo pretreatment and post-treatment with parthenolide improved the hemodynamic profile and reduced plasma nitrate/nitrite and lung neutrophil infiltration in a dose-dependent fashion. Vascular hyporeactivity of ex vivo aortas was ameliorated. Treatment with parthenolide also abolished nitrotyrosine formation, PARS expression, and apoptosis and reduced iNOS mRNA content in thoracic aortas. DNA binding of NF-kappaB was inhibited by parthenolide in the lung, whereas degradation of IkappaBalpha was unchanged. In a separate set of experiments, pretreatment or post-treatment with parthenolide significantly improved survival in mice challenged with endotoxin. We conclude that parthenolide exerts beneficial effects during endotoxic shock through inhibition of NF-kappaB.

Animals↗

PubMed2002

Interactions between the heat shock response and the nuclear factor-kappa B signaling pathway.

The heat shock response (HSR) and the nuclear factor (NF)-kappa B signaling pathway are two fundamental cellular responses. Various laboratories have documented in vitro and in vivo interactions between the HSR and NF-kappa B activation when they are activated sequentially. For example, induction of the HSR before a proinflammatory signal inhibits NF-kappa B activation and NF-kappa B-dependent proinflammatory gene expression. The central point of control appears to be at the level of I kappa B alpha phosphorylation as demonstrated by HSR-mediated inhibition of I kappa B kinase activation and HSR-mediated induction of intracellular phosphatase activity. In addition, induction of the HSR can independently increase de novo expression of the I kappa B alpha gene, thereby providing another potential mechanism through which the HSR can modulate cellular proinflammatory signaling. Another level of interaction is illustrated by the observation that various pharmacologic inhibitors of the NF-kappa B pathway are capable of simultaneously inducing the HSR. In direct contrast, induction of the HSR after a proinflammatory signal can lead to programmed cell death. Further understanding of how these two fundamental cellular responses interact at the molecular level holds the potential to elucidate some of the molecular interactions that occur during disease states common to critical care medicine.

Animals↗

PubMed2002

Interactions between the heat shock response and the nuclear factor-kappaB signaling pathway.

The heat shock response (HSR) and the nuclear factor (NF)-kappaB signaling pathway are two fundamental cellular responses. Various laboratories have documented in vitro and in vivo interactions between the HSR and NF-kappaB activation when they are activated sequentially. For example, induction of the HSR before a proinflammatory signal inhibits NF-kappaB activation and NF-kappaB-dependent proinflammatory gene expression. The central point of control appears to be at the level of IkappaBalpha phosphorylation as demonstrated by HSR-mediated inhibition of IkappaB kinase activation and HSR-mediated induction of intracellular phosphatase activity. In addition, induction of the HSR can independently increase de novo expression of the IkappaBalpha gene, thereby providing another potential mechanism through which the HSR can modulate cellular proinflammatory signaling. Another level of interaction is illustrated by the observation that various pharmacologic inhibitors of the NF-kappaB pathway are capable of simultaneously inducing the HSR. In direct contrast, induction of the HSR after a proinflammatory signal can lead to programmed cell death. Further understanding of how these two fundamental cellular responses interact at the molecular level holds the potential to elucidate some of the molecular interactions that occur during disease states common to critical care medicine.

Journal Article↗

PubMed2001

Role of diacylglycerol in PKD recruitment to the TGN and protein transport to the plasma membrane.

Protein kinase D (PKD) is a cytosolic serine-threonine kinase that binds to the trans-Golgi network (TGN) and regulates the fission of transport carriers specifically destined to the cell surface. PKD was found to bind diacylglycerol (DAG), and this binding was necessary for its recruitment to the TGN. Reducing cellular levels of DAG inhibited PKD recruitment and blocked protein transport from the TGN to the cell surface. Thus, a DAG-dependent, PKD-mediated signaling regulates the formation of transport carriers from the TGN in mammalian cells.

Carboxylic Acids↗