Biomedical subjects

P K Arora

Publications and source records attributed to P K Arora.

At least 19 recordsLinked to original sources

PubMed1992

Impaired calcium mobilization in CD4+ and CD8+ T cells in a retrovirus-induced immunodeficiency syndrome, murine AIDS.

After infection with LP-BM5 murine leukemia viruses, susceptible strains of mice develop a severe and progressive immunodeficiency disease, termed murine AIDS (MAIDS), features of which include markedly impaired T cell response to mitogens or specific Ag stimulation and decreased production of IL-2. Since an elevation of intracellular calcium concentration resulting from binding of Ag to the TCR is associated with IL-2 production, T cells from mice either uninfected or infected with LP-BM5 murine leukemia viruses were examined by a calcium mobilization assay. Both CD4+ and CD8+ T cells from infected mice manifested impaired calcium mobilization responses upon in vitro stimulation with anti-CD3 mAb or Con A. The abnormalities appeared early after virus inoculation and showed no difference in time course between subsets of T cells. Frequencies of prestimulation calcium-positive cells among both CD4+ and CD8+ cells in mice with MAIDS were significantly higher than those for uninfected mice. These abnormalities were associated with presence of the MAIDS-inducing defective virus genome, but were not induced by infection of mice genetically resistant to development of MAIDS or with nonpathogenic helper murine leukemia virus, a virus component that induces high spontaneous proliferation of T cells, even in MAIDS-resistant mice.

Animals↗

PubMed1992

Alterations in behavior, steroid hormones and natural killer cell activity in male transgenic TGF alpha mice.

The expression of transforming growth factor alpha (TGF alpha) is widely distributed throughout many normal and neoplastic tissues, but its physiological significance remains unclear. We have utilized male transgenic mice overexpressing the gene encoding human TGF alpha in multiple tissues to further identify those functions which are influenced by this protein. Male TGF alpha mice develop hepatocellular carcinoma at the age of 10-15 months. At the age of 2-3 months these mice, compared to age matched CD-1 controls, spent significantly longer times immobile in Porsolt's swim test, a model of stress and depressive behavior, and exhibiting aggressive behavior in the resident-intruder test. In contrast, the transgenic TGF alpha mice did not differ from the controls in either the plusmaze test of anxiety, or in their voluntary alcohol intake. Significantly, the TGF alpha mice exhibited a 25% lower Natural Killer (NK) cell activity and a four-fold increase in the plasma levels of 17-beta-estradiol (E2) than the controls. No significant changes in plasma testosterone or corticosterone levels were noted. The results indicate that transgenic male mice overexpressing TGF alpha exhibit behaviors characteristic of both an impaired ability to cope with stress and an increased aggressivity. The TGF alpha mice also show reduced NK cell activity and increased plasma estradiol concentrations. The present data suggest that TGF alpha may be important in influencing behavioral, immunological and hormonal systems prior to the onset of tumors. It remains to be determined whether hepatocarcinoma is associated with the direct proliferative and transforming effects of TGF alpha and/or indirect effects mediated through immune, hormonal and behavioral mechanisms.

Aggression↗

PubMed1992

Microglial-produced nitric oxide and reactive nitrogen oxides mediate neuronal cell death.

The role of inflammatory cytokines in the pathogenesis of neurological diseases is not well understood. The neurotoxic effects of cytokines could be mediated by immunostimulation of glial cells to produce toxic concentrations of nitric oxide (NO) and reactive nitrogen oxides. Cultured microglia and meningeal fibroblasts, but not Type 1 astrocytes, were induced by lipopolysaccharides and cytokines to synthesize NO and reactive nitrogen oxides from L-arginine. In co-cultures of immunostimulated microglia and cerebellar granule neurons, neurotoxicity was blocked by an inhibitor of NO synthase, NG-nitroarginine, and by oxyhemoglobin, which inactivates NO. Microglial-induced neurotoxicity was also partially attenuated by the N-methyl-D-aspartate (NMDA) receptor antagonists, MK-801 and 2-amino-5-phosphovalerate (APV). Superoxide dismutase, which stabilizes NO through inactivation of superoxide anion, augmented microglial-mediated neurotoxicity either alone or in combination with MK-801 or APV. Hence, immunostimulated microglia mediate neurotoxicity by NO, reactive nitrogen oxides, superoxide anion and NMDA-like substances. These findings suggest a novel role for microglial-produced NO and reactive nitrogen oxides as a neurotoxic agent in neurodegenerative disease states.

Amino Acid Oxidoreductases↗

PubMed1992

Immunoenhancing effects of alprazolam, a benzodiazepine receptor agonist.

The effects of alprazolam (ALP), a triazolobenzodiazepine with high affinity for "central" benzodiazepine receptors, were examined on several parameters of immune function in mice. NK, MLR, and mitogen-induced lymphocyte proliferation were all significantly increased 2 hr after administration of low doses (0.02-1.0 mg/kg) of ALP. Twenty four hr later, similar but less robust immunoenhancing effects were observed. These measures of immune functions were not affected by higher doses of ALP (5-10 mg/kg). The immunoenhancing effects of ALP did not appear related to serum corticosterone levels. These and other findings demonstrate that the GABA/benzodiazepine receptor chloride channel complex can bidirectionally modulate immune function.

Alprazolam↗

PubMed1992

Ethanol inhibits mitogen-induced calcium mobilization in mouse splenocytes.

Ethanol inhibited the mitogen-induced initial increase in cytoplasmic free-calcium [Ca2+]i in mouse splenocytes. This effect was concentration-dependent, reversible, and observed at pharmacologically relevant concentrations (24-166mM). Other short-chain alcohols such as propanol, butanol, and pentanol also inhibited this mitogen-induced increase in [Ca2+]i. The potencies of these alcohols to produce this effect were highly correlated (r = 0.98, p less than 0.001) with their membrane/buffer partition coefficients. Analysis of mouse splenocyte subpopulations demonstrated that this effect was manifest in both B and T lymphocytes. Within T lymphocyte subpopulations, both CD4+ and CD8+ T cells were affected. These results suggest that the inhibition of [Ca2+]i increase may be an early event mediating ethanol-induced immunosuppression and that this may be a predisposing factor to infection and malignancies associated with alcoholism.

Alcoholism↗

PubMed1992

Central nervous system infection in a murine retrovirus-induced immunodeficiency syndrome.

Astrocyte-enriched primary glial cultures (AGC) from C57BL/6 mice were found to be highly susceptible to infection with the replication competent components of LP-BM5, consisting of the ecotropic and mink cell focus-inducing (MCF) helper murine leukemia viruses (MuLVs). The presence in infected AGC of defective LP-BM5 MuLV genome, a critical component for induction of the disease referred to as murine AIDS, was confirmed by Southern blot hybridization using a probe reactive with the p12 gag sequence of the 4.9 kb defective genome. Electron microscopic studies demonstrated C-type retrovirus particles in both astrocytes and microglial cells. In vivo studies demonstrated that the ecotropic MuLVs and the defective genome could be detected within AGC obtained form either 14-day-old mice following intraperitoneal inoculation or 7-day-old mice following intracranial inoculation. These findings suggest that: (1) the central nervous system (CNS) infection is present at an early stage in murine AIDS, (2) both astrocytes and microglial cells are possible CNS targets in which helper MuLVs replicate, and (3) these cells can harbor the defective genome that is a critical component for disease induction.

Animals↗

PubMed1992

Spatial learning impairment in a murine model of AIDS.

Mice infected with an immunosuppressive murine leukemia virus (MuLV) mixture, LP-BM5, displayed profound and selective deficits in spatial learning in a modified Morris water maze. These deficits appeared before the appearance of gross neurological impairment or histopathological changes in the central nervous system. Thus, LP-BM5-infected mice displayed deficits in several aspects of trained performance compared to controls. Furthermore, a failure to exhibit any evidence of task acquisition in this maze was observed almost twice as frequently (P less than 0.0005) in infected mice as in uninfected controls. Moreover, in the absence of gross visual, motoric, or motivational impairment, LP-BM5 MuLV-infected animals exhibited neither the target directed search pattern nor the spatial preference characteristic of controls. The spatial learning and memory deficit described here is the first report of cognitive impairment accompanying viral-induced immunosuppression in a nonprimate species.

Animals↗

PubMed1991

Quantitative analysis of calcium (Ca2+) mobilization after stimulation with mitogens or anti-CD3 antibodies. Simultaneous fluo-3 and immunofluorescence flow cytometry.

A method is described for flow microfluorometric analysis of calcium mobilization in immune cells. This method is based on dual-color analysis of heterogeneous cell populations using fluo-3 and phycoerythrin (PE)-conjugated monoclonal antibody (mAb). This technique allows the detection of fluo-3 fluorescence as a measure of an increase in cytoplasmic free calcium ([Ca2+]i) while simultaneously discriminating PE-mAb-labeled cells without using wavelength ratio imaging. This method provides a unique way to distinguish patterns of calcium mobilization within a heterogeneous cell population.

Aniline Compounds↗

PubMed1991

Morphine-induced thymic hypoplasia is glucocorticoid-dependent.

Mice administered morphine as a s.c. pellet implant exhibit a marked and sustained thymic hypoplasia as well as suppression of T lymphocyte functions. In the present study, the effects of morphine on thymocyte differentiation were characterized. Morphine produced a significant decrease in both the number and proportion of CD4+/CD8+ double positive (DP) cells. The percentage of the CD4+/CD8-, CD4-/CD8+, and CD4-/CD8- double negative subsets in these mice was proportionally increased. Morphine also increased the proportion of cells expressing either the epsilon-chain of the CD3 complex or the IL-2R. The initial reduction in the proportion of DP thymocytes appeared fully recovered by 10 days post-implantation, although the number of DP thymocytes gradually returned to normal over a 3-wk period. Morphine administration resulted in a marked increase in serum corticosterone levels, and a single injection of dexamethasone mimicked the effects of morphine on thymus differentiation. Furthermore, adrenalectomy abolished the morphine-induced decrease in CD4+/CD8+ thymocytes relative to a sham-operated group. The present findings are consistent with the hypothesis that morphine-induced thymic hypoplasia may be mediated by an increase in the circulating levels of corticosterone.

Adrenalectomy↗

PubMed1991

Stress modulates calcium mobilization in immune cells.

Both acute and chronic restraint stress modulated mitogen-induced increases in cytoplasmic free-calcium concentrations ([Ca2+]i) in mouse spleen cells. Dual-color analysis of lymphocyte subpopulations demonstrated that acute (2 hour) restraint stress suppressed mitogen-stimulated increases in [Ca2+]i in CD4+ T cells, but enhanced [Ca2+]i in CD8+ T cells. Chronic restraint stress (2 hours daily for up to 21 days) resulted in a significant suppression of mitogen-stimulated increases in [Ca2+]i in CD4+ T cells at 3 and 7 days, but not at 21 days. CD8+ T cells were unaffected by chronic stress. Chronic stress (for 7 days) had a modest suppressive effect on mitogen-induced Ca2+ responses in B cells. Within T lymphocyte subpopulations, both acute and chronic stress predominantly affected CD4+ T cells, which may induce a functional reversal of the CD4/CD8 ratios in vivo. Such a reversal could result in suppression of a variety of immune responses such as lymphocyte proliferation and antigen-specific antibody production. These findings indicate that the inhibitory effects of stress on calcium mobilization in lymphocytes may be an early event mediating stress-induced immunosuppression.

Acute Disease↗

PubMed1991

Interleukin-1 potentiation of beta-endorphin secretion and the dynamics of interleukin-1 internalization in pituitary cells.

1. This study demonstrates that human recombinant interleukin-1 (IL-1) stimulates beta-endorphin release and potentiates the secretion of beta-endorphin in both a mouse anterior pituitary cell line AtT-20 and rat pituitary cell cultures. 2. In pituitary cell cultures, prolonged treatment with phorbol ester had no effect on IL-1-induced beta-endorphin release, but abolished the potentiating effects of IL-1 on vasopressin-induced beta-endorphin secretion. 3. The enhancement of CRF-stimulated beta-endorphin release by IL-1 was also reduced in normal pituitary cell cultures following depletion of protein kinase C. 4. The late IL-1-induced secretion of beta-endorphin does not require the continuous presence of the cytokine. 5. Incubation of monolayers with 125I-IL-1 alpha (10(-9) M) at 8 degrees C and then at 37 degrees C for various times revealed that IL-1 alpha was internalized. There was a progressive increase in the ratio of cytoplasmic to cell-surface-associated 125I-IL-1 alpha. 6. These results indicate that the IL-1-induced beta-endorphin release and its potentiation of beta-endorphin secretion involves internalization of this cytokine, perhaps via cell surface IL-1 receptors.

Animals↗

PubMed1991

Inhibition of calcium mobilization is an early event in opiate-induced immunosuppression.

Morphine administered as a subcutaneous implant inhibits the initial increase in cytoplasmic free-calcium [Ca2+]i induced by mitogens in mouse splenocytes. This effect was not reproduced by incubation of splenocytes with morphine (10(-8)-10(-4) M). Analysis of splenocyte subpopulations demonstrates that this effect was manifest in both B and T cells. However, within T cell subpopulations, CD4+ but not CD8+ cells were affected. Adrenalectomy abolished this effect of morphine in CD4+ T but not CD4-, CD8- spleen cells (most likely Thy 1.2- B cells). Moreover, simultaneous administration of the opiate antagonist naltrexone blocked the effect of morphine in CD4-, CD8- spleen cells, but not in CD4+ T cells. These data indicate that the effects of morphine on mitogen-stimulated increase in [Ca2+]i may be mediated through distinct glucocorticoid-dependent and -independent mechanisms. The morphine-induced inhibition of an increase in [Ca2+]i in immune cells reported here may be an early event mediating opiate-induced immunosuppression.

Animals↗

PubMed1991

Dopaminergic neurotoxicity in vivo and inhibition of mitochondrial respiration in vitro by possible endogenous pyridinium-like substances.

Elucidation of the mechanism(s) by which 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) and its active metabolite 1-methyl-4-phenylpyridinium (MPP+) cause parkinsonism in humans and other primates has prompted consideration of possible endogenous MPTP/MPP(+)-like neurotoxins in the etiology of idiopathic Parkinson's disease. Here we examined inhibition of mitochondrial respiration in vitro and neurotoxicity in rats in vivo produced by beta-carbolinium compounds that are presumed to form following Pictet-Spengler cyclization of serotonin. We also evaluated N-methylisoquinolinium, a putative endogenous neurotoxin, in the same manner. The latter compound exhibited MPP(+)-like mitochondrial respiratory inhibition, whereas the beta-carbolinium compounds, although more potent inhibitors of electron transport, exhibited weak accumulation-dependent enhancement of inhibition in intact mitochondria. It is interesting that the beta-carbolinium compounds inhibited succinate- as well as glutamate-supported respiration, and are best described as inhibitor-uncouplers. The results of partitioning experiments suggest that both the low accumulation potential and the inhibition of succinate respiration may be a consequence of the beta-carboliniums being in equilibrium with neutral "anhydro" bases. Relative to MPP+, all compounds tested had weak dopaminergic uptake activity in vitro and weak dopaminergic toxicity in vivo, consistent with other findings of relatively low neurotoxic potential for presumed endogenous pyridiniums.

1-Methyl-4-phenylpyridinium↗

PubMed1990

Inhibition of mitochondrial respiration by analogues of the dopaminergic neurotoxin 1-methyl-4-phenylpyridinium: structural requirements for accumulation-dependent enhanced inhibitory potency on intact mitochondria.

Analogues of 1-methyl-4-phenylpyridinium (MPP+), the neurotoxic metabolite of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, were evaluated for inhibition of respiration in intact mitochondria (Mw) and in electron transport particles (ETP). MPP+ exhibits relatively weak inhibitory activity in ETP, but potent inhibition in Mw occurs on account of its energy-dependent accumulation inside mitochondria. The permeant anion tetraphenylborate potentiates the inhibition in both Mw and ETP. Replacement of the 4-phenyl ring of MPP+ by a variety of aromatic and nonaromatic rings, and of the N-methylpyridinium group by other cationic aromatic heterocycles, preserves the inhibitory patterns seen for MPP+. The general observation of enhanced inhibitory potency in Mw for all these permanently charged cations is consistent with our contention that energy-dependent accumulation inside mitochondria represents a passive Nernstian concentration in response to the transmembrane electrochemical gradient. Nonetheless, the magnitude of the inhibitory potentiation seen in Mw relative to ETP varies widely with structure. In particular, less lipophilic analogues, especially those bearing a localized, rather than resonance-stabilized, permanent positive charge, exhibit similar inhibitory activity to MPP+ in ETP, but the inhibition in Mw is not comparably enhanced. For these same analogues, the inhibitory activity in ETP is only weakly potentiated by tetraphenylborate. Since succinate was found to completely reverse the respiratory inhibition in Mw induced by all types of MPP+ analogues investigated, a common site 1 inhibition appears to be involved; thus the different inhibitory patterns observed must be due to structural factors governing membrane transport and distribution properties.

1-Methyl-4-phenylpyridinium↗

PubMed1990

Strain-dependent association between immune function and paw preference in mice.

The relationship between immune function and the preferred direction of behavioral asymmetry was examined in several mouse strains. Mixed leukocyte reaction, natural killer cell activity, cytotoxic T lymphocyte response and lymphoproliferation in response to mitogens were investigated in animals with left or right paw preference. From the 7 strains and substrains examined, it appeared that differences in immune function between left and right pawed mice, when present, vary in directionality. Thus, in C3H/HeJ and 129/J, left pawed mice had higher immune responses than right pawed mice, whereas in C3H/HeNCr MTV- and BALB/cJ animals, the reverse was found. In C3H/HeNCr MTV+, C57BL/6J and Collin's heterogenous control population for the high/low asymmetry lines, no differences between animals with left or right paw preference were found. The statistical significance of these differences were not uniform for all the immune parameters studied. These data indicate that the association between immune function and preference for using the left versus right paw is a strain-dependent phenomenon and may suggest that the inconsistent evidence for an association between immune deficiency and left-handedness could be due to genetic heterogeneity among subpopulations.

Animals↗

PubMed1990

Morphine-induced immune alterations in vivo.

The high incidence of human immunodeficiency virus (HIV) seropositivity among drug abusers prompted us to examine in an animal model the effects of morphine on aspects of the immune system that may be specifically related to HIV infection. We now report a robust, sustained elevation in the ratio of CD4+/CD8+ cells in the spleen and thymus of mice chronically treated with morphine. Since CD4+ cells have been reported to be target cells for HIV, these alterations, in concert with a marked cellular atrophy that appears to be restricted to organs of the immune system, suggest that opiates may serve as cofactors in altering the immune status of the host and thus contribute to the increased susceptibility to HIV infection and eventual development of AIDS in opiate abusers.

Animals↗

PubMed1990

Characterization of human B cell (DK) and promonocyte (U937) clones after HIV-1 exposure: accumulation of viral reverse transcriptase activity in cells and early syncytia induction against SupT1 cells.

The kinetics of HIV-1 infection were compared among human B (DK), promonocyte (U937), T-B hybrid (CEMX174), and T (H9) cell lines. Just like H9 cells, CEMX174 cells exhibited strong syncytia induction capacity against highly HIV-1-sensitive CD4+ T cells (SupT1) and had high reverse transcriptase (RT) release in the supernatant. DK and U937 cells showed syncytia induction capacity by 72 hr, but RT activity in the culture supernatant (extracellular RT) increased much later. RT activity in cell lysates (intracellular RT) became detectable at 12-15 days. The inverted extracellular/intracellular RT ratio and syncytia induction capacity were also observed in chronically infected DK (DK-IIIB) and U937 (U937-IIIB) cell lines and subclones from U937-IIIB. Further, the coculture of H9 with DK-IIIB (which indicates no detectable extracellular RT release) showed remarkable amplification of extracellular RT with significant increase of T-B double marker hybrids (H9-DK-IIIB). Our results suggest that B cells and/or monocytes/macrophages may acquire fusing capacity against CD4+ T cells in early stages of the infection and that these cell-to-cell interactions may also lead to a reduction in the number of CD4+ T cells. Further, these T-B and T monocyte hybrids may serve as temporal sites for viral replication. These in vitro studies may provide clues to the possible immunopathological roles of HIV-1-infected B cells and monocytes/macrophages and may help in understanding the mechanisms of viral burden on an infected host.

B-Lymphocytes↗

PubMed1990

Structure-neurotoxicity trends of analogues of 1-methyl-4-phenylpyridinium (MPP+), the cytotoxic metabolite of the dopaminergic neurotoxin MPTP.

The dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) derives from its metabolism to 1-methyl-4-phenyl-pyridinium cation (MPP+), which is then selectively accumulated in dopaminergic neurons. In an effort to assess the structural requirements governing MPP+ cytotoxicity, we evaluated dopaminergic toxicity of MPP+ analogues 3 weeks after their microinfusion into rat substantia nigra. We also evaluated the substrate suitability of MPP+ analogues for high-affinity dopamine uptake in striatal synaptosomes by measuring their ability to induce specific dopamine release. The intranigral neurotoxicity of MPP+ analogues in vivo correlates mainly with their in vitro inhibitory activity on mitochondrial respiration, consistent with a compromise in cellular energy production as the principal mechanism of MPTP-induced cell death. This study extends the structure-neurotoxicity data base beyond that obtainable using MPTP analogues, since many of these are not metabolized to pyridinium compounds. Such information is crucial to assess which possible endogenous or exogenous compounds may exert MPTP/MPP(+)-like toxicity.

1-Methyl-4-phenylpyridinium↗