Biomedical subjects

S Nagpal

Publications and source records attributed to S Nagpal.

At least 55 records · Page 3Linked to original sources

PubMed1996

Negative regulation of two hyperproliferative keratinocyte differentiation markers by a retinoic acid receptor-specific retinoid: insight into the mechanism of retinoid action in psoriasis.

Retinoids down-regulate the expression of metalloproteinases, cytokines, and other genes involved in cell proliferation and inflammation. Tazarotene (AGN 190168), a retinoic acid receptor (RAR)-specific retinoid, is effective in the treatment of psoriasis, a hyperproliferative and inflammatory skin disease. Because negative regulation of genes appears to be important in the antiproliferative and antiinflammatory action of retinoids, we studied the down-regulation of genes in skin raft cultures by this antipsoriatic retinoid. By subtraction hybridization, we found that migration inhibitory factor-related protein (MRP-8) and skin-derived anti-leukoproteinase (SKALP) are down-regulated by AGN 190168. MRP-8 and SKALP are overexpressed in psoriatic lesions as compared to the normal epidermis, and they are markers of hyperproliferative keratinocyte differentiation. We also show that MRP-8 expression is retinoid inhibitable in cultured keratinocytes induced to differentiate with 10% serum or IFN-gamma, and that MRP-8 is inhibited by RAR but not by retinoid X receptor-specific retinoids in a dose-dependent manner. Finally, MRP-8, SKALP, and the previously characterized differentiation marker, transglutaminase I, are all down-regulated in vivo in psoriatic lesions after treatment with AGN 190168 in comparison to placebo. Taken together, these data suggest that these markers may be down-regulated by tazarotene in psoriasis through direct action on keratinocyte gene expression rather than by an overall tazarotene effect on lesional therapeutic status.

Antigens, Differentiation↗

PubMed1996

Differential regulation of human ectocervical epithelial cell line proliferation and differentiation by retinoid X receptor- and retinoic acid receptor-specific retinoids.

Retinoids are important regulators of human papillomavirus (HPV)-immortalized cervical epithelial cell differentiation and have been successfully used in the treatment of HPV-involved cervical cancer. In the present study, we examine the effects of a series of natural and synthetic retinoids on differentiation and proliferation of HPV-16-positive lines, ECE16-1 and CaSki. Retinoic acid receptor alpha (RAR alpha), RAR gamma, and retinoid X receptor alpha (RXR alpha) are the major retinoid receptor subtypes expressed when ECE16-1 cells are grown in retinoid-free medium. Our results indicate that ligands that interact with RARs only or both RARs and RXRs, including all-trans-retinoic acid (all-trans-RA), 9-cis-retinoic acid (9-cis-RA), 13-cis-retinoic acid (13-cis-RA), and several synthetic retinoids, suppress ECE16-1 cell proliferation, regulate expression of the retinoid-responsive differentiation marker cytokeratin K5, and increase RAR beta mRNA levels. In contrast, ligands that specifically interact with RXRs do not suppress proliferation and are less efficient regulators of gene expression. CaSki cells express greatly reduced RAR and RXR levels compared to ECE16-1 cells. However, both RAR- and RXR-specific ligands increase CaSki number by > or = 20%. In addition, RXR-specific ligands suppress cytokeratin K5 mRNA levels slightly, compared to RAR-specific ligands that strongly suppress K5 mRNA levels. We also compare the effects of these agents on the proliferation of other cervical cell lines, including ECE16-D2, ME180, and SiHa cells. ECE16-D2 and ME180 cells are growth suppressed by RAR-specific, but not RXR-specific, retinoids. SiHa cells are not responsive to either class of retinoid. Our results indicate that: (a) the response of different human cervical cell lines varies following treatment with receptor type-specific retinoids; and (b) the relationship between retinoid regulation of proliferation and differentiation can be uncoupled.

Cell Differentiation↗

PubMed1995

Separation of transactivation and AP1 antagonism functions of retinoic acid receptor alpha.

Retinoic acid receptors (RARs) regulate gene expression either by directly binding to the RAR-responsive elements or by antagonizing the action of c-Jun/c-Fos (AP1). AP1 is involved in the expression of metalloproteases, cytokines and other factors which play critical roles in the turnover of extracellular matrix, inflammation and hyperproliferation in diseases such as psoriasis, rheumatoid arthritis and in tumor metastases. We demonstrate here that synthetic retinoids inhibit 12-O-tetradecanoylphorbol-14-acetate-induced transcription from the stromelysin AP1 motif through RAR alpha, -beta, and -gamma. Interestingly, these diaryl acetylenic retinoids, which are potent agonists only for RAR beta and RAR gamma, but not for RAR alpha, in transactivation assays, are able to inhibit AP1-dependent gene expression through RAR alpha. Thus these analogs can differentially affect the transactivation and AP1 antagonistic functions of RAR alpha. These results demonstrate that the transactivation and AP1 antagonistic functions are separable, and it should be possible to develop retinoids that are completely specific for AP1 antagonism through all RARs. Furthermore, using an RAR-selective ligand, we also demonstrate the separation of ligand binding and AP1 antagonism functions of RARs.

Base Sequence↗

PubMed1994

Churg-Strauss syndrome with nongiant cell eosinophilic temporal arteritis.

The classic (giant cell) temporal arteritis occasionally coexists with other systemic vasculitides or one of the connective tissue diseases, and occasionally, necrotizing vasculitis has been diagnosed serendipitously in temporal artery biopsies. The association of the classic (giant cell) temporal arteritis with Churg-Strauss syndrome in the same patient occurs only rarely. Involvement of the temporal arteries by nongiant cell eosinophilic vasculitis in Churg-Strauss syndrome, to our knowledge, has not been documented, and we describe one such unusual case.

Churg-Strauss Syndrome↗

PubMed1993

Identification of tropomyosin as the major shrimp allergen and characterization of its IgE-binding epitopes.

The major heat-stable shrimp allergen (designated as Sa-II), capable of provoking IgE-mediated immediate type hypersensitivity reactions after the ingestion of cooked shrimp, has been shown to be a 34-kDa heat-stable protein containing 300 amino acid residues. Here, we report that a comparison of amino acid sequences of different peptides generated by proteolysis of Sa-II revealed an 86% homology with tropomyosin from Drosophila melanogaster, suggesting that Sa-II could be the shrimp muscle protein tropomyosin. To establish that Sa-II is indeed tropomyosin, the latter was isolated from uncooked shrimp (Penaeus indicus) and its physicochemical and immunochemical properties were compared with those of Sa-II. Both tropomyosin and Sa-II had the same molecular mass and focused in the isoelectric pH range of 4.8 to 5.4. In the presence of 6 M urea, the mobility of both Sa-II and shrimp tropomyosin shifted to give an apparent molecular mass of 50 kDa, which is a characteristic property of tropomyosins. Shrimp tropomyosin bound to specific IgE antibodies in the sera of shrimp-sensitive patients as assessed by competitive ELISA inhibition and Western blot analysis. Tryptic maps of both Sa-II and tropomyosin as obtained by reverse phase HPLC were superimposable. Dot-blot and competitive ELISA inhibition using sera of shrimp-sensitive patients revealed that antigenic as well as allergenic activities were associated with two peptide fractions. These IgE-binding tryptic peptides were purified and sequenced. Mouse anti-anti-idiotypic antibodies raised against Sa-II specific human idiotypic antibodies recognized not only tropomyosin but also the two allergenic peptides, thus suggesting that these peptides represent the major IgE binding epitopes of tropomyosin. A comparison of the amino acid sequence of shrimp tropomyosin in the region of IgE binding epitopes (residues 50-66 and 153-161) with the corresponding regions of tropomyosins from different vertebrates confirmed lack of allergenic cross-reactivity between tropomyosins from phylogenetically distinct species.

Allergens↗

PubMed1993

Retinoic acid signal transduction pathways.

Complexity in the retinoid signaling system arises from a combination of several forms of retinoic acid which possess differential activities, multiple cytoplasmic binding proteins and nuclear receptors that have distinct ligand specificities and functional properties, and the existence of polymorphic retinoic acid response elements. Additional diversity appears to be generated by heterodimeric interactions between the two classes of nuclear retinoic acid receptors and between retinoic acid receptors and some other members of the nuclear receptor superfamily. Thus, a complex array of combinatorial effects is beginning to emerge that may account for the pleiotropic effects of retinoids.

Amino Acid Sequence↗

PubMed1993

RARs and RXRs: evidence for two autonomous transactivation functions (AF-1 and AF-2) and heterodimerization in vivo.

We have previously reported that the AB regions of retinoic acid receptors (RARs and RXRs) contain a transcriptional activation function capable of modulating the activity of the ligand-dependent activation function present in the C-terminal DE regions of these receptors. However, we could not demonstrate that these AB regions possess an autonomous activation function similar to the AF-1s found in the AB regions of steroid hormone receptors. Using the mouse CRBPII promoter as a reporter gene, we now report that the AB regions of RAR alpha, beta and gamma, as well as those of RXR alpha and gamma, contain an autonomous, ligand-independent activation function, AF-1, which can efficiently synergize with AF-2s. Moreover, AF-1s account for the ligand-independent, constitutive activation of transcription by RXR alpha and gamma. We also show that RARs and RXRs preferentially heterodimerize in solution in cultured cells in vivo, through the dimerization interface present in their E region, irrespective of the presence of all-trans or 9-cis retinoic acid. Furthermore, our results indicate that homodimeric interactions are not observed in cultured cells in vivo under conditions where heterodimeric interactions readily occur, which is in agreement with previous observations showing the preferential binding of RAR-RXR heterodimers to RA response elements in vitro.

Animals↗

PubMed1993

Serum lipoperoxide levels in surgical stress of abdominal hysterectomy.

In continuation of our studies on stress situations in female reproductive life span, serum lipid peroxide levels in terms of malondialdehyde (nmol/ml) have been determined in females [(n = 40) (aged between 35-40 years)] to undergo total abdominal hysterectomy (due to dysfunctional uterine bleeding). There occurred a statistically significant though within physiological limits, progressive rise in serum lipid peroxide levels right from preoperative stage 3.51, per operatively 3.56 to a maximum of 4.10 postoperative stage I with a tendency of fall at postoperative stage II 3.94 in comparison with self control on admission 2.97. It is suggestive of the balancing and protective role of scavenging enzyme system like superoxide dismutase also backed by improvement in health status of abdominal hysterectomy patients in terms of ambulation, free intake of food and behavioural positive attitude within 24 hours following operation presumably due to relief from stress of DUB. It is felt from the results of the present investigation that patients undergoing abdominal hysterectomy were free from free radical toxicity.

Adult↗

PubMed1992

Promoter context- and response element-dependent specificity of the transcriptional activation and modulating functions of retinoic acid receptors.

Using several naturally occurring and synthetic retinoic acid (RA)-responsive reporter genes, we show that the patterns of transcriptional activation by various retinoic acid receptor (RAR) and retinoid X receptor (RXR) forms vary according to the nature of the RA response element and the context of the stimulated promoter. We demonstrate the presence of autonomous, ligand-inducible, and promoter context-dependent transactivation functions (AF-2s) located in the C-terminal region of all RARs and RXRs. In addition, promoter context-specific modulating transactivation functions are associated with the N-terminal A and B regions of RARs and RXRs. We also show that these transactivation and modulating functions exhibit response-element specificity. The modulating functions display a marked specificity in their cooperation with the AF-2 transactivation functions, cooperation that depends on the receptor origin of the modulating and transactivation functions and the promoter context of the RA-responsive gene, thus accounting for the specific transactivation properties of RAR and RXR types.

Animals↗

PubMed1992

RAR-beta 4, a retinoic acid receptor isoform is generated from RAR-beta 2 by alternative splicing and usage of a CUG initiator codon.

An isoform of retinoic acid receptor beta, RAR-beta 4, has been identified. RAR-beta 4 is expressed under the control of the same retinoic acid-responsive promoter as RAR-beta 2. RAR-beta 4, which is generated by alternative splicing from the same primary transcripts as RAR-beta 2, is initiated by a non-AUG codon, CUG. The amino acid sequence of RAR-beta 4 in regions B-F is identical to that of the other RAR-beta isoforms beta 1, beta 2, and beta 3. However, the RAR-beta 4 A region is much shorter (4 amino acids long) than those of these isoforms. RAR-beta 4 exhibits a tissue-specific pattern of expression and distinct transcriptional activation properties when compared with the other RAR-beta isoforms.

Animals↗

PubMed1992

Induction of anti-DNA IgG and IgE antibodies in BALB/c mice.

Immunization of BALB/c mice with denatured DNA (dnDNA)-methylated bovine serum albumin (MBSA) complex along with aluminium hydroxide gel as adjuvant, resulted in the induction of anti-DNA antibodies of both IgG and IgE isotypes demonstrable by avidin-biotin micro enzyme-linked immunosorbent assay (ELISA) and solid phase radioimmunoassay (SPRIA), respectively. In contrast to the high levels of IgG2a and IgG2b anti-DNA antibodies observed in SLE-prone autoimmune mice, more than 90% of the anti-DNA antibodies of IgG isotype were found to be of IgG1 subclass. Specificity of both IgG and IgE antibodies which recognized activated DNA, dnDNA and double-stranded DNA but not RNA was established by competitive ELISA and SPRIA inhibition assays. These antibodies cross-reacted with cibacron blue and chondroitin sulfate but not with various other proteoglycans, nucleosides and nucleotides. Passive cutaneous anaphylaxis reaction in rats showed that these antibodies are capable of inducing in vivo degranulation of mast cells in a dose-dependent manner. These studies lend support to the concept that IgE antibodies directed against DNA may mediate mast cell degranulation and thus contribute to immediate-type hypersensitivity phenomena including hives seen in patients with systemic lupus erythematosus and to the localization of IgE-nucleic acid complexes.

Animals↗

PubMed1991

Immediate hypersensitivity to Parthenium hysterophorus. II. Clinical studies on the prevalence of Parthenium rhinitis.

The airborne pollen of the South American weed, Parthenium hysterophorus (American feverfew), accidentally introduced into India was found to be responsible for severe allergic rhinitis. A random clinical survey conducted on 2035 residents of Bangalore city with the aid of questionnaires and skin tests revealed that 7.1% of the study population was suffering from allergic rhinitis due to exposure to Parthenium pollen. Skin-prick tests performed on 1294 clinic patients suffering from nasobronchial allergy during the past 4 years have also shown that 42.5% were sensitive to Parthenium pollen. IgE and IgG antibodies specific for Parthenium pollen allergens were demonstrable in the sera of Parthenium-sensitive rhinitis patients. The specificity of these antibodies to Parthenium allergens was established by ELISA. A 7- to 11-fold higher stimulation was observed when lymphocytes from two Parthenium-sensitive rhinitis patients were treated in vitro with Parthenium pollen extract. To our knowledge, nowhere in the world has such a high incidence of allergic rhinitis due to a single pollen ever been reported.

Adolescent↗

PubMed1991

Characterization of a potent varicella-zoster virus-encoded trans-repressor.

Using a transient expression assay in Vero cells, we have shown that the protein product from gene 61 of varicella-zoster virus (VZV) can repress the function of the VZV encoded trans-activators on putative viral immediate-early, early, and late gene promoters. The repression is exerted at the transcriptional level and requires functional gene 61 protein. This trans-repressor is the herpes simplex type 1 ICP0 (a trans-activator) homolog, as defined by gene location, the sharing of a cysteine-rich putative zinc-binding finger in the amino-terminal region, and limited amino acid homology. Open reading frame 61 (ORF61)-mediated trans-repression appears to be specific for VZV-encoded trans-activators in that it has no effect on simian virus 40 and Rous sarcoma virus promoters. Moreover, it does not inhibit trans-activation of the human T-lymphotropic virus type I and human immunodeficiency virus long terminal repeats by tax and tat genes, respectively. We constructed plasmids with mutations in ORF61 and tested them for their ability to inhibit trans-activator (VZV genes 4 and 62)-mediated activation of the viral thymidine kinase promoter-chloramphenicol acetyltransferase construct. Mutants containing interruptions in ORF61 lost their trans-repressing ability, as demonstrated at both the protein and steady-state RNA levels. These results suggest that the ORF61 protein product can mediate down-regulation of VZV gene expression.

Animals↗

PubMed1991

IgG4 autoantibodies to DNA in systemic lupus erythematosus patients.

The presence of DNA-specific IgG4 antibodies was demonstrated in the sera of patients with systemic lupus erythematosus (SLE) by a microtiter solid-phase radioimmunoassay. A patient with distal interphalangeal swelling and extensive ulcers in the oral cavity, seronegative for anti-DNA antibodies of the IgG isotype, was found to have anti-DNA autoantibodies exclusively of the IgG4 subclass. These autoantibodies directed against the dsDNA conformation cross-reacted with chondroitin sulfate, dermatan sulfate and heparin.

Adult↗

PubMed1991

Serum lipoperoxides in induced and spontaneous abortions.

Abortion, primarily as a measure of population control, certainly continues to be an emotional, frustrating and stressful event. In continuation of our work on stressful situations in the female life span and biochemical parameters, serum lipid peroxide levels in terms of malondialdehyde (nmol/ml) have been determined in females undergoing abortion [suction curettage (n = 30), Emcredil-induced abortion (n = 30) and spontaneous abortion (n = 40)] and were compared with appropriate gestational controls. Irrespective of the type of abortion, the serum lipid peroxide levels before abortion [mean malondialdehyde concentrations (nmol/ml): suction curettage 2.67, Emcredil-induced abortion 3.22, and spontaneous abortion 3.49] were found to be significantly elevated in comparison with those after abortion (suction curettage 1.91, Emcredil 1.97 and spontaneous abortion 1.95), indicating a maximum at peak time of stress and a minimum at the end of stress. The levels of serum lipid peroxide encountered before abortion were found to be significantly elevated in case of Emcredil-induced abortion and spontaneous abortion when compared with controls (second trimester mean levels 1.82 and first trimester 2.4) whereas the levels before suction curettage were found to be nonsignificant in comparison with controls, indicating a lesser degree of stress. It is felt that monitoring of serum lipid peroxide levels in serum and tissues (placenta), backed by scavenging enzyme superoxide dismutase, can be more helpful for corroborating safety and the risk of free radical toxicity in pregnancy and abortion.

Abortion, Induced↗

PubMed1990

Negative regulation of the rat stromelysin gene promoter by retinoic acid is mediated by an AP1 binding site.

Stromelysin is a member of the metalloproteinase family which plays an important role in extracellular matrix remodelling during many normal and disease processes. We show here that in polyomavirus-transformed rat embryo fibroblast cells (PyT21), the transcription from the stromelysin gene is repressed by the vitamin A derivative retinoic acid (RA). Furthermore, expression vectors encoding the human RA receptors hRAR-alpha, hRAR-beta and hRAR-gamma repress chloramphenicol acetyltransferase (CAT) expression from stromelysin promoter-CAT gene expression vectors in RA-treated PyT21 and human HeLa cells, as determined by transient transfection assays. Through mutation and deletion analysis, we show that the RA dependent repression is mediated by a 25 bp region from nucleotide positions -72 to -48 of the rat stromelysin 5'-flanking DNA sequence. Further mutation analysis of this region indicates that the DNA sequence required for RA dependent repression colocalizes with an AP1 binding site which is essential for promoter activity. We show also that RA represses the transcriptional activity of a reporter gene containing a TPA responding AP1 binding site driving the HSV tk promoter. Thus the RAR-RA complex appears to repress transcription of the stromelysin gene by blocking activation by positive regulatory factors. However, we found no evidence supporting the possibility that the RA dependent repression could be due to RAR binding to the AP1 binding site or to the AP1 components c-fos and c-jun.

Animals↗

PubMed1990

Detection of IgG, IgA, IgM and IgE antibodies in invasive amoebiasis in endemic areas.

Entamoeba histolytica-specific serum IgG, IgA, IgM and IgE antibodies were assayed in cases of amoebiasis in an endemic area. Patient groups consisted of amoebic liver abscess (n = 18), preabscess hepatic amoebiasis (n = 22) and amoebic colitis (n = 30). Control subjects comprised 26 asymptomatic cyst passers, 13 giardiasis cases, 20 typhoid patients and 24 non-amoebic individuals. Serum IgG was assayed by ELISA, using a monoclonal anti IgG beta-galactosidase (IgG beta-gal) conjugate, a polyclonal avidin biotin horse radish peroxidase (AB-HRP), and a polyclonal anti IgG horse radish peroxidase (IgG HRP) conjugate. IgA and IgM were assayed by the beta-gal ELISA and IgE by AB-HRP. Diagnostically significant IgG and IgA while lower IgM and IgE antibody levels were seen in extraintestinal cases. About 40% of suspected pre-abscess hepatic amoebiasis cases were confirmed by antibody estimation. All isotype levels in most dysentery cases were in the range of the controls.

Animals↗

PubMed1990

Demonstration of IgE antibodies to nucleic acid antigens in patients with SLE.

Using a combination of avidin-biotin microELISA and solid phase radioimmunoassay, we examined sera from 23 patients with systemic lupus erythematosus (SLE), two patients with established sensitivity to ingested shrimp, and 15 healthy normal subjects. In addition to IgG antibodies, varying amounts of IgE antibodies specific for native DNA (nDNA), denatured or single-stranded DNA (dnDNA), RNA, and tRNA were demonstrable in the sera of SLE patients, but not in the sera of normal subjects. A comparison of the specificity of nucleic acid-specific IgE antibodies present in the sera of shrimp-sensitive patients with those present in the sera of seven SLE patients revealed that the IgE antibodies in the sera of shrimp-sensitive patients specifically recognized shrimp tRNA but not yeast tRNA, calf thymus RNA, or calf thymus DNA, while those present in the sera of patients with SLE recognized all these nucleic acid antigens. The IgE antibodies directed against nDNA, dnDNA, RNA, and tRNA may mediate mast cell and basophil degranulation and thus contribute both to immediate-type hypersensitivity phenomena including hives seen in patients with SLE and to the localization of IgE-nucleic acid complexes in target tissues.

Antibodies, Antinuclear↗