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Biomedical subjects

S Sriram

Publications and source records attributed to S Sriram.

At least 19 recordsLinked to original sources
PubMed2001

CSF oligoclonal bands in MS include antibodies against Chlamydophila antigens.

BACKGROUND: Considerable evidence suggests the role of an infectious agent in MS. The presence of Chlamydophila pneumoniae in CSF from patients with MS was shown earlier; to further examine this association the reactivity of the oligoclonal antibody response in the CSF of patients with MS to C pneumoniae antigens was determined and compared with other antigens. METHODS: Seventeen patients with MS and 14 control subjects with other neurologic disease were studied. Affinity-driven immunoblot studies and solid-phase adsorption of CSF oligoclonal bands by elementary body antigens of C pneumoniae, viral antigens (measles and herpes simplex virus-1), bacterial antigen (Escherichia coli and Staphylococcus aureus), and heat shock protein-60 were performed. RESULTS: Affinity-driven immunoblot studies demonstrated reactivity of oligoclonal bands in CSF samples from 16 patients with MS against elementary body antigens of C pneumoniae. None of the control subjects showed a prominent reactivity to elementary body antigens of C pneumoniae. In 14 of 17 patients with MS examined, oligoclonal bands were adsorbed either partially or completely from the CSF by elementary body antigens of C pneumoniae, but not by myelin basic protein, heat shock protein-60, or bacterial or viral antigens. In three patients with subacute sclerosing panencephalitis, adsorption of oligoclonal bands was seen with measles virus antigens but not with elementary body antigens of C pneumoniae. CONCLUSIONS: Oligoclonal bands in CSF of patients with MS include antibodies against Chlamydophila antigens.

Adult↗
PubMed2001

Inhibition of CD40 signaling pathway by tyrphostin A1 reduces secretion of IL-12 in macrophage, Th1 cell development and experimental allergic encephalomyelitis in SJL/J mice.

Activation of antigen presenting cells through the interaction of CD40 with its ligand is a critical co-stimulatory signal for IL-12 production and Th1 differentiation. Tyrphostins are organic molecules that inhibit the phosphorylation of protein tyrosine kinases. We show that tyrphostin A1 inhibits CD40L-stimulated IL-12 production in macrophage cultures and antigen-induced generation of Th1 cells. Our data also show that tyrphostin A1 blocks CD40L-induced translocation of NF-kappaB to the nucleus, and reduces the activation of IL-12 p40 gene. In vivo therapy with A1 leads to decrease in generation of myelin basic protein (MBP) specific encephalitogenic T cells. In addition, treatment of SJL/J mice with A1 results in attenuation of experimental allergic encephalomyelitis (EAE).

Animals↗
PubMed2001

Purification and characterization of an extracellular alpha-glucosidase protein from Trichoderma viride which degrades a phytotoxin associated with sheath blight disease in rice.

AIMS: To purify and characterize an extracellular alpha-glucosidase from Trichoderma viride capable of inactivating a host-specific phytotoxin, designated RS toxin, produced by the rice sheath blight pathogen, Rhizoctonia solani Kühn. METHODS AND RESULTS: The host-specific RS toxin was purified from both culture filtrates (culture filtrate toxin, CFTox) and R. solani-inoculated rice sheaths (sheath blight toxin, SBTox). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analyses of extracellular proteins, purified from a biocontrol fungus T. viride (TvMNT7) grown on SBTox and CFTox separately, were carried out. The antifungal activity of the purified high molecular weight protein (110 kDa) was studied against RS toxin as well as on the sclerotial germination and mycelial growth of R. solani. Enzyme assay and Western blot analysis with the antirabbit TvMNT7 110-kDa protein indicated that the protein was an alpha-glucosidase. The 110-kDa protein was highly specific to RS toxin and its Michaelis-Menten constant value was 0.40 mmol l-1 when p-nitrophenyl alpha-D-glucopyranoside was used as the substrate. The isoelectric point of the protein was 5.2. N-terminal sequencing of the alpha-glucosidase protein showed that its amino acid sequence showed no homology with other known alpha-glucosidases. CONCLUSION: This appears to be the first report of the purification and characterization of an alpha-glucosidase capable of inactivating a host-specific toxin of fungal origin. The alpha-glucosidase is specific to RS toxin and is different from the known alpha-glucosidases. SIGNIFICANCE AND IMPACT OF THE STUDY: As RS toxin could be inactivated by the microbial alpha-glucosidase enzyme, isolation of the gene that codes for the enzyme from T. viride and transfer of the gene to rice plants would lead to enhanced resistance against sheath blight pathogen by inactivation of RS toxin.

Amino Acid Sequence↗
PubMed2001

Regulation by IFN-beta of inducible nitric oxide synthase and interleukin-12/p40 in murine macrophages cultured in the presence of Chlamydia pneumoniae antigens.

Chlamydia pneumoniae has been demonstrated in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS). Interferon-beta (IFN-beta) has favorable effects on the clinical course of MS. We investigated whether the beneficial effects of IFN-beta in MS may involve its role in regulating nitric oxide (NO) and interleukin-12 (IL-12) in macrophages, as these immune modulators form part of the innate immune response to intracellular pathogens, such as C. pneumoniae. Murine macrophages in cultures exposed to elementary body antigens or recombinant major outer membrane protein (rMOMP) of C. pneumoniae demonstrate a significant increase in NO as well as production of IL-12/p40 in culture supernatants compared with basal levels. Addition of murine IFN-beta increased NO activity in murine macrophages cultured with chlamydial antigens. Addition of neutralizing anti-IFN-beta antibody prevented the NO increase. In contrast to its effect on inducible NO synthase (iNOS), IFN-beta reduced induction of IL-12/p40 following culture with either elementary body antigens or rMOMP. Inhibition was reversed with anti-IFN-beta antibody. If C. pneumoniae infection is responsible for the inflammatory response in the pathogenesis of MS, the beneficial effects of IFN-beta in MS may be due to its enhancing intracellular NO activity while inhibiting secretion of the proinflammatory cytokine, IL-12.

Animals↗
PubMed2001

Chlamydia pneumoniae infection of the central nervous system.

Chlamydia pneumoniae is a common respiratory pathogen that is now being implicated in a number of chronic diseases. That the organism can infect vascular endothelium, macrophages and smooth muscle cells suggests that it may play a role in many systemic diseases. The present review focuses on the possibility that the central nervous system can also be a target of this agent. The tropism of C. pneumoniae to the neural tissue suggests it may play a role in diverse neurologic diseases, including Alzheimer's disease, multiple sclerosis and giant-cell arteritis.

Alzheimer Disease↗
PubMed2001

Immunotherapy of inflammatory demyelinating diseases of the central nervous system.

Inflammatory demyelinating diseases comprise a heterogeneous group of disorders that affect the peripheral and central nervous system. Multiple sclerosis (MS) is the most common disease affecting the CNS white matter. Close similarities between MS and the animal model of the disease, experimental allergic encephalitis (EAE), have suggested that MS might be an autoimmune disease, which is triggered by an infectious agent. Our laboratory has directed its effort in identifying and designing therapies that interfere with key signaling pathways that mediate CNS inflammation in experimental allergic encephalitis. These have included naturally occurring cytokines such as TGFbeta and synthetic small molecules, lysofyline and tyrphostin, which inhibit the inflammatory response and prevent the development of EAE.

Adult↗
PubMed2001

An infectious basis for multiple sclerosis: perspectives on the role of Chlamydia pneumoniae and other agents.

The aetiology of multiple sclerosis (MS) remains unknown. Epidemiological, clinical and pathological data support the theory that MS is a complex disease/syndrome with many factors affecting its development and progression. It may be appropriate to regard MS as a syndrome with differing clinical and pathological features occurring along a spectrum. Patients with MS are more likely to have an affected relative than are individuals without MS, which suggests that there is a genetic component to this illness. Despite this genetic susceptibility, 85% of MS patients do not have an affected relative and only 1 in 3 monozygotic (identical) twins develops MS if the other twin already has it. These data strongly suggest that environmental factors influence the development of MS. Many putative infectious agents have been proposed to be involved in the aetiology of MS. Although research into identifying MS-causative agents dates back for more than 5 decades, no agent has yet emerged with any consensus as the cause of MS. This controversy is due to a number of factors, including lack of specificity of an agent to MS, lack of reproducibility in other laboratories, inappropriate controls, laboratory contamination and lack of a standard and easily reproducible assay system. Chlamydia pneumoniae is a recently described pathogen that may have a role in the pathogenesis of MS. C. pneumoniae is an intracellular bacterial organism that is infectious to humans. It has recently been detected in the cerebrospinal fluid (CSF) of MS patients but not in that of patients with other neurological diseases. There is also a case report of a patient with CNS C. pneumoniae infection and rapidly progressive MS responding to antimicrobial therapy directed against this pathogen. An association between C. pneumoniae in the CSF and MS is now apparent, but its role in the development of MS remains unknown. Further work exploring the role of C. pneumoniae in inflammatory demyelination is required. This may be accomplished either by developing an animal model or in a therapeutic trial in patients with MS.

Chlamydia Infections↗
PubMed2000

Amelioration of CR-EAE with lisofylline: effects on mRNA levels of IL-12 and IFN-gamma in the CNS.

CR-EAE is a Th1-mediated inflammatory autoimmune demyelinating disease of the CNS and serves as a model of human multiple sclerosis. Our previous studies have shown the protective effect of orally administered lisofylline in the prevention of active and passively induced acute EAE. In our present studies we have examined the efficacy and mechanism of action of lisofylline on CR-EAE. Lisofylline decreased the number and severity of paralytic attacks in mice with relapsing EAE. The reduction of clinical disease correlated with decreased levels of mRNA levels of IFN-gamma but not of mRNA levels of IL-12. These studies suggest that lisofylline may be an effective therapeutic for established Th1 mediated autoimmune disease and that it acts by blocking IL-12R signaling and not IL-12 production in vivo.

Animals↗
PubMed2000

Interacting molecular loops in the mammalian circadian clock.

We show that, in the mouse, the core mechanism for the master circadian clock consists of interacting positive and negative transcription and translation feedback loops. Analysis of Clock/Clock mutant mice, homozygous Period2(Brdm1) mutants, and Cryptochrome-deficient mice reveals substantially altered Bmal1 rhythms, consistent with a dominant role of PERIOD2 in the positive regulation of the Bmal1 loop. In vitro analysis of CRYPTOCHROME inhibition of CLOCK: BMAL1-mediated transcription shows that the inhibition is through direct protein:protein interactions, independent of the PERIOD and TIMELESS proteins. PERIOD2 is a positive regulator of the Bmal1 loop, and CRYPTOCHROMES are the negative regulators of the Period and Cryptochrome cycles.

ARNTL Transcription Factors↗
PubMed2000

Induction of interleukin-12/p40 by superantigens in macrophages is mediated by activation of nuclear factor-kappaB.

Multimerization of the MHC class II molecule by superantigens results in activation of cellular signal transduction pathways in macrophage and B cells. Here we show that superantigen staphylococcal enterotoxin B (SEB) induces IL-12/p40 secretion in macrophages. SEB-induced expression of the IL-12/p40 gene involves activation and nuclear translocation of nuclear factor kappaB (NF-kappaB). The NF-kappaB heterodimer bound to the NF-kappaB consensus sequence of the IL-12/p40 gene promoter is p50/C-Rel. Inhibition of PKC and PKA activation results in suppression of activation and translocation of NF-kappaB. We conclude that signals for IL-12/p40 gene transcription from MHC class II molecules follow activation of PKC and PKA, which in turn leads to the activation and translocation of NF-kappaB to the nucleus. Our study suggests that superantigens are capable of influencing the nature of the immune response by regulating cytokine production. Induction of IL-12 production by superantigens may therefore play a role in the regulation of Th 1-mediated immune response and autoimmune disease.

Animals↗
PubMed2000

A time-less function for mouse timeless.

The timeless (tim) gene is essential for circadian clock function in Drosophila melanogaster. A putative mouse homolog, mTimeless (mTim), has been difficult to place in the circadian clock of mammals. Here we show that mTim is essential for embryonic development, but does not have substantiated circadian function.

Animals↗
PubMed2000

Inactivation of phytotoxin produced by the rice sheath blight pathogen Rhizoctonia solani.

The rice sheath blight pathogen, Rhizoctonia solani, produces a toxin designated as RS-toxin, a carbohydrate compound containing mainly alpha-glucose and mannose. Different microflora were tested for RS-toxin inactivation. Isolates of Trichoderma viride inactivated this toxin when it was provided as the sole food source, and these isolates reduced the severity of toxin-induced symptoms and electrolyte leakage from rice cells. The best-performing isolate, TvMNT7, produced two extracellular proteins of 110 and 17 kDa. The high molecular mass protein was shown to have alpha-glucosidase activity. The purified 110 kDa protein was able to reduce RS-toxin activity.

Blotting, Western↗
PubMed2000

Failure to identify alveolar echinococcosis in trappers from South Dakota in spite of high prevalence of Echinococcus multilocularis in wild canids.

Echinococcus multilocularis causes a rare but potentially lethal zoonotic disease in humans. This tapeworm has been known to be endemic in foxes (Vulpes vulpes) and coyotes (Canis latrans) within the northern United States since the 1960s. One purpose of this study was to provide recent data on the prevalence of E. multilocularis in foxes and coyotes from eastern South Dakota. In a survey conducted from 1987 to 1991 and involving 137 foxes and 9 coyotes from this area, 74.5% of the foxes and 4 of the coyotes were infected. To assess the possible prevalence of alveolar echinococcosis in a group at presumptive high risk, we also conducted a serological survey of members of the South Dakota Trappers Association in 1990 and 1991. Serum samples from 115 trappers were evaluated for the presence of E. multilocularis antibodies using enzyme-linked immunosorbent assay tests involving a purified antigen called Em2, a crude E. multilocularis antigen, and a recombinant E. multilocularis antigen called II/3-10. None of the trappers showed antibody evidence for the presence of E. multilocularis. Roughly half of the surveyed individuals had trapped more than 50 foxes during their life, and almost one-fourth had trapped more than 1,000 foxes.

Adolescent↗
PubMed1999

mCRY1 and mCRY2 are essential components of the negative limb of the circadian clock feedback loop.

We determined that two mouse cryptochrome genes, mCry1 and mCry2, act in the negative limb of the clock feedback loop. In cell lines, mPER proteins (alone or in combination) have modest effects on their cellular location and ability to inhibit CLOCK:BMAL1 -mediated transcription. This suggested cryptochrome involvement in the negative limb of the feedback loop. Indeed, mCry1 and mCry2 RNA levels are reduced in the central and peripheral clocks of Clock/Clock mutant mice. mCRY1 and mCRY2 are nuclear proteins that interact with each of the mPER proteins, translocate each mPER protein from cytoplasm to nucleus, and are rhythmically expressed in the suprachiasmatic circadian clock. Luciferase reporter gene assays show that mCRY1 or mCRY2 alone abrogates CLOCK:BMAL1-E box-mediated transcription. The mPER and mCRY proteins appear to inhibit the transcriptional complex differentially.

3T3 Cells↗
PubMed1999

Tyrphostin B42 inhibits IL-12-induced tyrosine phosphorylation and activation of Janus kinase-2 and prevents experimental allergic encephalomyelitis.

IL-12 is a macrophage-derived cytokine that induces proliferation, cytokine production, and cytotoxic activity of T and NK cells. Signaling through its receptor, IL-12 induces these cellular responses by tyrosine phosphorylation and activation of Janus kinase-2 (Jak-2), Tyk-2, Stat3, and Stat4. We have used tyrphostin B42 (AG490), a Jak-2 inhibitor, to determine the role of Jak-2 kinase in IL-12 signaling and IL-12-induced T cell functions. Treatment of activated T cells with tyrphostin B42 inhibited the IL-12-induced tyrosine phosphorylation and activation of Jak-2 without affecting Tyk-2 kinase. In contrast, treatment with tyrphostin A1 inhibited the tyrosine phosphorylation of Tyk-2 but not that of Jak-2 kinase. Inhibition of either Jak-2 or Tyk-2 leads to a decrease in the IL-12-induced tyrosine phosphorylation of Stat3, but not of Stat4, protein. While inhibition of Jak-2 lead to programmed cell death, the inhibition of Jak-2 or Tyk-2 resulted a decrease in IFN-gamma production. We have further tested the in vivo effects of tyrphostin B42 in experimental allergic encephalomyelitis, a Th1 cell-mediated autoimmune disease. In vivo treatment with tyrphostin B42 decreased the proliferation and IFN-gamma production of neural Ag-specific T cells. Treatment of mice with tyrphostin B42 also reduced the incidence and severity of active and passive EAE. These results suggest that tyrphostin B42 prevents EAE by inhibiting IL-12 signaling and IL-12-mediated Th1 differentiation in vivo.

Animals↗
PubMed1999

Superantigens augment antigen-specific Th1 responses by inducing IL-12 production in macrophages.

Superantigens (SAg) are microbial proteins that mediate antigen-presenting cell (APC)-T cell interaction by cross-linking MHC class II molecules with subsets of TcRVbeta. SAgs are implicated in the pathogenesis of several infectious, inflammatory, and autoimmune diseases. In this study, we examined the influence of SEB on interleukin-12 (IL-12) production and the activation of antigen-specific Th1 responses. Addition of SEB augmented the antigen-induced proliferation of HS-17, a murine MBPp91-103 peptide-specific TcRVbeta6+ CD4+ Th1 clone. SEB augments HS-17 T cell proliferation through its interaction with IA(S) molecules on macrophages, but not with the TcRVbeta6 on HS-17 cells. On binding to IA(S), SEB induces IL-12 production in macrophages, which in turn augments antigen-induced proliferation of HS-17 T cells. Treatment with anti-IA(S) nmAb 10-3.6 inhibited the antigen- and SEB-induced IL-12 production and T cell proliferation. These results suggest that SAgs augment antigen-specific T cell responses by inducing IL-12 production in macrophages.

Adjuvants, Immunologic↗