Biomedical subjects

Khalequz Zaman

Publications and source records attributed to Khalequz Zaman.

10 recordsLinked to original sources

PubMed2006

Activation of chloride transport in CF airway epithelial cell lines and primary CF nasal epithelial cells by S-nitrosoglutathione.

BACKGROUND: It has been suggested that low microM concentrations of S-nitrosoglutathione (GSNO), an endogenous bronchodilator, may promote maturation of the defective cystic fibrosis (CF) transmembrane conductance regulator (CFTR). Because nitric oxide (NO) and GSNO levels appear to be low in the CF airway, there is an interest in the possibility that GSNO replacement could be of therapeutic benefit in CF. METHODS: The effect of GSNO on chloride (Cl-) transport was investigated in primary nasal epithelial cells obtained from CF patients homozygous for the delF508 mutation, as well as in two CF cell lines (CFBE and CFSME), using both a fluorescent Cl- indicator and X-ray microanalysis. Maturation of delF508 CFTR was determined by immunoblotting. RESULTS: Treatment with 60 microM GSNO for 4 hours increased cAMP-induced chloride efflux in nasal epithelial cells from 18 out of 21 CF patients, but did not significantly affect Cl- efflux in cells from healthy controls. This Cl- efflux was confirmed by measurements with a fluorescent Cl- indicator in the CFBE and CFSME cell lines. The effect of GSNO on Cl- efflux in CFBE cells could be inhibited both by a specific thiazolidinone CFTR inhibitor (CFTRinh-172) and by 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid (H2DIDS). X-ray microanalysis showed that, following 4 hours incubation with 60 microM GSNO, cAMP agonists caused a decrease in the cellular Cl- concentration in CFBE cells, corresponding to Cl- efflux. GSNO exposure resulted in an increase in the protein expression and maturation, as shown by immunoblot analysis. GSNO did not increase the cytosolic Ca2+ concentration in cultured airway epithelial cells. CONCLUSION: Previous studies have suggested that treatment with GSNO promotes maturation of delF508-CFTR, consistent with our results in this study. Here we show that GSNO increases chloride efflux, both in the two CF cell lines and in primary nasal epithelial cells from delF508-CF patients. This effect is at least in part mediated by CFTR. GSNO may be a candidate for pharmacological treatment of the defective chloride transport in CF epithelial cells.

Cell Line↗

PubMed2006

S-nitrosylating agents: a novel class of compounds that increase cystic fibrosis transmembrane conductance regulator expression and maturation in epithelial cells.

The endogenous bronchodilator, S-nitrosoglutathione (GSNO), increases expression, maturation, and function of both the wild-type and the DeltaF508 mutant of the cystic fibrosis transmembrane conductance regulatory protein (CFTR). Though transcriptional mechanisms of action have been identified, GSNO seems also to have post-transcriptional effects on CFTR maturation. Here, we report that 1) GSNO is only one of a class of S-nitrosylating agents that, at low micromolar concentrations, increase DeltaF508 and wild-type CFTR expression and maturation; 2) NO itself (at these concentrations) and 8-bromocyclic GMP are minimally active on CFTR; 3) a novel agent, S-nitrosoglutathione diethyl ester, bypasses the need for GSNO bioactivation by gamma-glutamyl transpeptidase to increase CFTR maturation; 4) surprisingly, expression-but not S-nitrosylation-of cysteine string proteins (Csp) 1 and 2 is increased by GSNO; 5) the effect of GSNO to increase full maturation of wild-type CFTR is inhibited by Csp silencing (si)RNA; 6) proteins relevant to CFTR trafficking are SNO-modified, and SNO proteins traffic through the endoplasmic reticulum (ER) and Golgi after GSNO exposure; and 7) GSNO alters the interactions of DeltaF508 CFTR with Csp and Hsc70 in the ER and Golgi. These data suggest that GSNO is one of a class of S-nitrosylating agents that act independently of the classic NO radical/cyclic GMP pathway to increase CFTR expression and maturation. They also suggest that the effect of GSNO is dependent on Csp and on intracellular SNO trafficking. We speculate that these data will be of relevance to the development of NO donor-based therapies for CF.

Cell Differentiation↗

PubMed2006

Endogenous S-nitrosoglutathione modifies 5-lipoxygenase expression in airway epithelial cells.

S-Nitrosoglutathione (GSNO) is an endogenous bronchodilator with several beneficial pulmonary effects. Levels are decreased in the asthmatic airway, and GSNO inhalation has been proposed as an asthma therapy. 5-lipoxygenase (5-LO) is the rate-limiting enzyme in the synthetic pathway for cysteinyl leukotrienes (CysLTs), bronchoconstricting agents that are overproduced in asthma. Here, we have studied the effect of GSNO on the expression of 5-LO in human airway A549 cell lines and in primary normal human tracheobronchial epithelial (NHBE) cells in vitro. GSNO at concentrations of 0.5-1 microM caused a 3- to 6-fold increase in 5-LO expression. However, GSNO at>5 microM significantly inhibited both 5-LO expression and LT production. We also found that airway epithelial cells had gamma-glutamyl transpeptidase (gamma-GT) activity. The effect of 1 microM GSNO on 5-LO expression was prevented by the gamma-GT inhibitor, acivicin, suggesting a convergence of GSNO and CysLT metabolic pathway that may be relevant to asthma. Our data demonstrate that GSNO levels 5microM suppresses 5-LO expression. These data suggest that GSNO might inhibit 5-LO expression in the clinical setting.

Arachidonate 5-Lipoxygenase↗

PubMed2006

Zinc supplementation and serum zinc during diarrhea.

OBJECTIVE: Zinc deficiency is very common in developing countries and is more pronounced during an episode of diarrhea. Supplementation with zinc improves diarrhea and might correct zinc deficiency in both the short and longer term. METHOD: We conducted a nested study within a cluster randomized treatment trial. Fifty children with diarrhea living in the zinc treated clusters, 50 children with diarrhea living in control clusters, and 50 healthy children living in the control clusters were enrolled. We assessed serum zinc at the start of the diarrhea episode, which was 1-3 days after supplementation began in zinc treated children, and again one week after the diarrhea ended and supplementation ceased. Baseline characteristics and serum zinc concentration were assessed. RESULTS: Serum zinc was low in 44% of healthy children at the first blood draw. Compared to healthy controls, serum zinc was 3.1 mmol/L higher among children with diarrhea who were supplemented with zinc at first blood draw and 1.3 mmol/L higher 3 weeks later. CONCLUSION: Zinc supplementation enhances serum zinc concentration when given as a treatment for diarrhea and helps children maintain a more adequate zinc status during the convalescent period.

Child, Preschool↗

PubMed2006

Prevalence of arsenic exposure and skin lesions. A population based survey in Matlab, Bangladesh.

STUDY OBJECTIVE: To assess prevalence of arsenic exposure through drinking water and skin lesions, and their variation by geographical area, age, sex, and socioeconomic conditions. DESIGN, SETTING, AND PARTICIPANTS: Skin lesion cases were identified by screening the entire population above 4 years of age (n = 166,934) living in Matlab, a rural area in Bangladesh, during January 2002 and August 2003. The process of case identification involved initial skin examinations in the field, followed by verification by physicians in a clinic, and final confirmation by two independent experts reviewing photographs. The tubewell water arsenic concentrations (n = 13,286) were analysed by atomic absorption spectrometry. Drinking water history since 1970 was obtained for each person. Exposure information was constructed using drinking water histories and data on water arsenic concentrations. MAIN RESULTS: The arsenic concentrations ranged from <1 to 3644 microg/l, and more than 70% of functioning tubewells exceeded the World Health Organisation guideline of 10 microg/l. Arsenic exposure had increased steadily from 1970s to the late 1990s, afterwards a decrease could be noted. In total, 504 skin lesions cases were identified, and the overall crude prevalence was 3/1000. Women had significantly higher cumulative exposure to arsenic, while men had significantly higher prevalence of skin lesions (SMR 158, 95% CI 133 to 188). The highest prevalence occurred in 35-44 age groups for both sexes. Arsenic exposure and skin lesions had a positive association with socioeconomic groups and achieved educational level. CONCLUSIONS: The result showed sex, age, and socioeconomic differentials in both exposure and skin lesions. Findings clearly showed the urgency of effective arsenic mitigation activities.

Adolescent↗

PubMed2006

S-nitrosothiols regulate cell-surface pH buffering by airway epithelial cells during the human immune response to rhinovirus.

Human rhinovirus infection is a common trigger for asthma exacerbations. Asthma exacerbations and rhinovirus infections are both associated with markedly decreased pH and ammonium levels in exhaled breath condensates. This observation is thought to be related, in part, to decreased activity of airway epithelial glutaminase. We studied whether direct rhinovirus infection and/or the host immune response to the infection decreased airway epithelial cell surface pH in vitro. Interferon-gamma and tumor necrosis factor-alpha, but not direct rhinovirus infection, decreased pH, an effect partly associated with decreased ammonium concentrations. This effect was 1) prevented by nitric oxide synthase inhibition; 2) independent of cyclic GMP; 3) associated with an increase in endogenous airway epithelial cell S-nitrosothiol concentration; 4) mimicked by the exogenous S-nitrosothiol, S-nitroso-N-acetyl cysteine; and 5) independent of glutaminase expression and activity. We then confirmed that decreased epithelial pH inhibits human rhinovirus replication in airway epithelial cells. These data suggest that a nitric oxide synthase-dependent host response to viral infection mediated by S-nitrosothiols, rather than direct infection itself, plays a role in decreased airway surface pH during human rhinovirus infection. This host immune response may serve to protect the lower airways from direct infection in the normal host. In patients with asthma, however, this fall in pH could be associated with the increased mucus production, augmented inflammatory cell degranulation, bronchoconstriction, and cough characteristic of an asthma exacerbation.

Cell Line↗

PubMed2005

Typing of human rotaviruses: nucleotide mismatches between the VP7 gene and primer are associated with genotyping failure.

BACKGROUND: Rotavirus genotyping is performed by using reverse transcription PCR with type-specific-primers. Because the high rotavirus mutation rate generates an extensive genomic variation, different G-type-specific primer sets are applied in different geographical locations. In Bangladesh, a significant proportion (36.9%) of the rotavirus strains isolated in 2002 could not be G-typed using the routinely used primer set. To investigate the reason why the strains were untypeable, nucleotide sequencing of the VP7 genes was performed. RESULTS: Four nucleotide substitutions at the G1 primer-binding site of the VP7 gene of Bangladeshi G1 rotaviruses rendered a major proportion of circulating strains untypeable using the routine primer set. Using an alternative primer set, we could identify G1 rotaviruses as the most prevalent genotype (44.8%), followed by G9 (21.7%), G2 (15.0%) and G4 (13.8%). CONCLUSION: Because of the natural variation in the rotaviral gene sequences, close monitoring of rotavirus genotyping methods is important.

Antigens, Viral↗

PubMed2005

S-nitrosothiol formation.

Protein and peptide S-nitrosothiols (SNOs) are involved in guanylate cyclase-independent signaling associated with nitric oxide synthase (NOS) activation. As a general rule, SNO formation requires the presence of an electron acceptor such as Cu2+. Various proteins have been identified that catalyze SNO formation, including NOS itself, ceruloplasmin, and hemoglobin. Biochemical evidence suggests the existence of other SNO synthases and NOS-associated proteins involved in SNO formation following NOS activation. Indeed, both hydrophilic and hydrophobic consensus motifs have been identified that favor protein S-nitrosylation. Inorganic SNO formation appears also to occur in biological systems at low pH levels and/or in membranes. Once formed, SNOs localized to specific cellular compartments signal specific effects, ranging from gene regulation to ion channel gating. Indeed, the number of cellular and physiological functions appreciated to be regulated through SNO synthesis, localization, and catabolism is increasing. Although research into SNO biosynthesis is in its infancy, the importance of this field of biochemistry has been confirmed repeatedly by investigators from a broad spectrum of disciplines.

Molecular Weight↗

PubMed2004

Concentration-dependent effects of endogenous S-nitrosoglutathione on gene regulation by specificity proteins Sp3 and Sp1.

The activities of certain nuclear regulatory proteins are modified by high concentrations of S-nitrosothiols associated with nitrosative stress. In the present study, we have studied the effect of physiological (low microM) concentrations of the endogenous S-nitrosothiol, GSNO (S-nitrosoglutathione), on the activities of nuclear regulatory proteins Sp3 and Sp1 (specificity proteins 3 and 1). Low concentrations of GSNO increased Sp3 binding, as well as Sp3-dependent transcription of the cystic fibrosis transmembrane conductance regulatory gene, cftr. However, higher GSNO levels prevented Sp3 binding, augmented Sp1 binding and prevented both cftr transcription and CFTR (cystic fibrosis transmembrane conductance regulator) expression. We conclude that low concentrations of GSNO favour Sp3 binding to 'housekeeping' genes such as cftr, whereas nitrosative stress-associated GSNO concentrations shut off Sp3-dependent transcription, possibly to redirect cellular resources. Since low micromolar concentrations of GSNO also increase the maturation and activity of a clinically common CFTR mutant, whereas higher concentrations have the opposite effect, these observations may have implications for dosing of S-nitrosylating agents used in cystic fibrosis clinical trials.

Animals↗

PubMed2003

Sp1 and Sp3 are oxidative stress-inducible, antideath transcription factors in cortical neurons.

Neuronal cell death in response to oxidative stress may reflect the failure of endogenous adaptive mechanisms. However, the transcriptional activators induced by oxidative stress in neurons that trigger adaptive genetic responses have yet to be fully elucidated. We report that basal DNA binding of the zinc finger transcription factors Sp1 and Sp3 is unexpectedly low in cortical neurons in vitro and is significantly induced by glutathione depletion-induced or hydrogen peroxide-induced oxidative stress in these cells. The increases in Sp1/Sp3 DNA binding reflect, in part, increased levels of Sp1 and Sp3 protein in the nuclei of cortical neurons. Similar induction of Sp1 and Sp3 protein is also observed in neurons in vivo in a chemical or a genetic model of Huntington's disease, two rodent models in which neuronal loss has been attributed to oxidative stress. Sustained high-level expression of full-length Sp1 or full-length Sp3, but not the Sp1 zinc finger DNA-binding domain alone, prevents death in response to oxidative stress, DNA damage, or both. Taken together, these results establish Sp1 and Sp3 as oxidative stress-induced transcription factors in cortical neurons that positively regulate neuronal survival.

Animals↗