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Biomedical subjects

R B Chapin

Publications and source records attributed to R B Chapin.

9 recordsLinked to original sources
PubMed1998

Morphine modulates NF kappa B activation in macrophages.

Chronic use of morphine affects the immune system and predisposes an individual to opportunistic infections. Macrophages play an important role in conferring a first line of defense against invading pathogens. Understanding the mechanisms by which morphine affects the functioning of macrophages would have significant therapeutic benefit in treatment against infections such as HIV and AIDS related syndromes. Two of the major cytokines secreted by activated macrophages are Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha). Our studies show that morphine differentially modulates lipopolysaccharide (LPS) induced expression of IL-6 and TNF-alpha. Nanomolar concentrations of morphine synergize with LPS and augment the secretion of both IL-6 and TNF-alpha. However, at micromolar concentrations morphine inhibits LPS induced synthesis of IL-6 and TNF-alpha. Expression of both these cytokine genes is dependent on the activation of a transcription factor, NF kappa B. Interestingly, morphine treatment also modulated the activation of NF kappa B by LPS. Pretreatment with a low dose of morphine (nanomolar) resulted in an increase in NF kappa B activation. In contrast pretreatment with a high dose of morphine (micromolar) led to a significant decrease in NF kappa B activation. Furthermore unlike the augmentation which was naloxone reversible, the inhibition of NF kappa B by morphine was not reversed by naloxone, suggesting the involvement of a nonclassical opioid receptor.

Animals↗
PubMed1997

Morphine inhibits transcriptional activation of IL-2 in mouse thymocytes.

Chronic treatment of mice with morphine affects the proliferation, differentiation, and function of immune cells. In the present study, we investigated the mechanism by which morphine inhibits phytohemagglutinin (PHA)/interleukin-1 (IL-1)-induced thymocyte proliferation. When compared to control cultures, morphine-treated thymocytes showed decreased steady-state levels of bioactive IL-2 and IL-2 mRNA. The reduced IL-2 concentration and reduced transcript levels correlated well with a decreased rate of synthesis of IL-2 mRNA as determined by nuclear runoff assays. Subsequent studies showed that morphine treatment affected transcriptional control elements of the IL-2 promoter by inhibiting the synthesis of a specific trans-activating nuclear factor, c-Fos. c-Fos mRNA levels measured by semiquantitative RT-PCR were significantly decreased in thymocytes following treatment with morphine and activation with PHA and IL-1. Under identical conditions, c-Jun mRNA levels were not altered. Electrophoretic mobility shift studies with the AP-1 consensus oligonucleotide showed significantly decreased levels of AP-1-protein complex formation in nuclear extracts prepared from morphine-treated cells. These studies demonstrate for the first time that opioid alkaloids such as morphine can impair mitogen-lymphokine-activated thymocyte proliferation by interfering with transcriptional activation of the IL-2 gene.

Animals↗
PubMed1996

The effect of surgical treatment following peritoneal sepsis on hepatic gene expression.

Peritoneal sepsis results in downregulation of the gene that codes for the hepatic mitochondrial enzyme carnitine palmitoyltransferase (CPT). The inhibition of hepatic CPT transcription by sepsis is thought to be mediated, in part, by increased expression of the leucine-zipper DNA transcription factor c-fos. In a cecal ligation and puncture (CLP) model, we examined the temporal effect of surgical treatment (cecal excision) on sepsis-induced inhibition of CPT gene expression. We investigated the hypothesis that Fos protein level will inversely correlate with the regulation of CPT gene expression. Specifically, we studied hepatic Fos nucleoprotein accumulation and CPT gene expression as measured by total mitochondrial CPT activity, CPT protein, and CPT mRNA. We investigated the following groups: (i) CLP followed by cecal excision 6, 12, or 24 hr following initial insult, (ii) concurrent CLP control group, and (iii) concurrent sham CLP reference group. When measured 48 hr following initial surgical insult, we conclude that: (i) in the absence of surgical treatment, peritoneal contamination results in a decrease in hepatic CPT gene expression and an increase in Fos nucleoprotein accumulation; (ii) surgical treatment at 6 or 12 hr following initial insult prevents the downregulation in hepatic CPT gene expression and does not result in Fos nucleoprotein accumulation; and (iii) surgical treatment at 24 hr following insult did not prevent the downregulation of hepatic CPT gene expression and results in an increase in hepatic Fos nucleoprotein accumulation. These data are consistent with the hypothesis that sepsis-induced regulation of hepatic c-fos gene expression, in part, is responsible for the downregulation of CPT gene expression.

Animals↗
PubMed1995

The possible role of a central nervous system dopaminergic mechanism in hepatic c-fos protein expression following peritoneal sepsis.

OBJECTIVE: To investigate the hypothesis that a central dopaminergic mechanism may regulate hepatic c-fos and c-jun gene expression following peritoneal sepsis. METHODS: First, dopamine or vehicle was instilled into a stereotaxically placed intracerebral-ventricular (ICV) cannula with or without D1 (SCH 23390) or D2 (haloperidol) antagonist pretreatment in a rat model, and the effect on hepatic c-fos or c-jun protein expression was investigated. Second, we investigated the effect of haloperidol and vehicle treatment following cecal ligation and puncture (CLP)-induced sepsis with respect to hepatic c-fos protein expression, c-jun protein expression, and survival. RESULTS: Intracerebral-ventricular dopamine treatment increased hepatic c-fos immunoreactive protein but had no effect on hepatic c-jun immunoreactive protein expression. Pretreatment with SCH 23390 inhibited ICV dopamine treatment-induced hepatic c-fos immunoreactive protein expression. Haloperidol pretreatment synergized with ICV dopamine treatment to overexpress hepatic c-fos protein. Haloperidol treatment significantly increased CLP-induced hepatic c-fos and c-jun protein expression and improved survival following CLP. CONCLUSIONS: Hepatic c-fos protein expression may be regulated, in part, by a central nervous system-mediated dopaminergic D1 receptor mechanism. Treatment with the D2 receptor antagonist, haloperidol, increases sepsis-induced hepatic c-fos and c-jun protein expression and improves survival following peritoneal contamination.

Animals↗
PubMed1995

Regulation of the transcription factor C/EBP alpha following peritoneal sepsis.

The transcription factors C/EBP alpha and C/EBP beta belong to the leucine-zipper C/EBP (CCAAT/enhancer binding protein) family of DNA-binding proteins. C/EBP alpha and C/EBP beta are expressed in the liver and are implicated in the control of transcriptional events following following sepsis. It is hypothesized that inhibition of C/EBP alpha gene expression following sepsis may lead to some of the phenotypic features we recognize as sepsis syndrome such as decreased visceral protein (albumin) synthesis. In this study we demonstrate that C/EBP alpha mRNA accumulation is transiently inhibited 12 hr following peritoneal insult, consistent with previous data. However, we demonstrate that (1) there is increased binding of hepatic nuclear protein to the C/EBP alpha DNA response element 48 hr following insult, (2) a marked increase in C/EBP alpha protein is observed 48 hr following CLP insult compared with no increase in hepatic C/EBP alpha protein at 12 hr postinsult, (3) the increase in hepatic C/EBP alpha protein at 48 hr following cecal ligation and puncture is not associated with an increase in C/EBP alpha mRNA accumulation, (4) the increase in hepatic C/EBP alpha protein is associated with an increase in C/EBP beta protein, and (5) hepatic albumin mRNA accumulation is decreased at 12 and 48 hr following insult and does not correlate with the C/EBP alpha protein synthesis. We conclude that the possible role of the transcription factor C/EBP alpha with respect to decreased albumin gene expression following sepsis must be reevaluated.

Albumins↗
PubMed1994

The role of programmed cell death (apoptosis) in thymic involution following sepsis.

OBJECTIVE: To test the hypothesis that thymic involution following peritoneal sepsis is secondary to thymocyte programmed cell death. DESIGN: We investigated the temporal response of thymic weight and thymic DNA fragmentation following peritoneal sepsis induced by cecal ligation and puncture in a rat model. We investigated the possible role of decreased interleukin (IL)-2 synthesis in the induction of apoptosis using rat thymocytes in primary culture. Finally, we studied IL-2 gene expression and IL-2 protein synthesis in phytohemagglutinin and IL-1 beta-treated thymocytes derived from the cecal ligation and puncture model of sepsis. RESULTS: We demonstrated that (1) there is a significant decrease in thymic weight and an increase in thymic DNA fragmentation with the characteristic apoptotic DNA "ladder" fragmentation pattern on agarose gel electrophoresis following peritoneal sepsis; (2) thymocytes in primary culture sustain a significant increase in thymocyte apoptosis following IL-2 withdrawal; and (3) peritoneal sepsis results in inhibition of phytohemagglutinin and IL-1 beta-induced thymocyte IL-2 messenger RNA accumulation and protein synthesis. CONCLUSIONS: Thymic involution following peritoneal sepsis is associated with increased thymocyte programmed cell death. Thymocyte apoptosis induced by sepsis may be the result, in part, of inhibition of IL-2 gene expression.

Animals↗
PubMed1994

Sepsis-induced release of interleukin-6 may activate the immediate-early gene program through a hypothalamic-hypophyseal mechanism.

BACKGROUND: The immediate-early gene c-fos has been implicated in transcriptional regulation after sepsis. We test the hypothesis that sepsis-induced central nervous system release of interleukin (IL)-6 regulates hepatic c-fos gene expression. METHODS: Using a stereotaxically placed intracerebral-ventricular (ICV) catheter in rats with and without hypophysectomy, we measured hepatic c-fos protein accumulation after treatment with either IL-6 or vehicle control. Using a rat cecal ligation and puncture (CLP) model, we studied the following groups: (1) sham-CLP, (2) CLP, (3) hypophysectomized sham-CLP, and (4) hypophysectomized CLP and measured hepatic c-fos mRNA. RESULTS: ICV IL-6 treatment increased hepatic c-fos protein in the IL-6-treated group compared with the vehicle-treated group, and hypophysectomy inhibited the ICV IL-6-mediated increase in c-fos protein. After peritoneal sepsis, CLP increased hepatic c-fos messenger RNA compared to either the sham-CLP or the hypophysectomized sham-CLP group, and hypophysectomy before CLP inhibited hepatic c-fos mRNA compared with the CLP group. CONCLUSIONS: ICV IL-6 results in an increase in hepatic fos protein that is mediated through a hypothalamic-hypophyseal mechanism. Peritoneal sepsis results in an increase in hepatic c-fos gene expression that may be, in part, mediated by central nervous system release of IL-6 through a hypothalamic-hypophyseal mechanism.

Animals↗