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Biomedical subjects

M S Harbuz

Publications and source records attributed to M S Harbuz.

At least 73 records · Page 4Linked to original sources
PubMed1997

An antisense oligodeoxynucleotide complementary to corticotropin-releasing hormone mRNA inhibits rat splenocyte proliferation in vitro.

Expression of neuropeptides in immune tissues has been implicated in the paracrine control of immune functions. The effects of the endogenous splenic neuropeptide corticotropin-releasing hormone (CRH) on immune cell proliferation were investigated by incubating splenocytes from adult male Wistar rats in vitro with a specific antisense oligodeoxynucleotide probe complementary to CRH mRNA. Incubation of cells with 1 microgram/ml phosphodiester antisense probe for 24 h prior to stimulation with concanavalin A (Con A) resulted in a 30-65% decrease in 3H-thymidine uptake compared to controls. In spleen cells incubated with a random base sequence (nonsense) probe the uptake of 3H-thymidine was not different to that in control cells. Incubation of cells with either antisense or nonsense phosphorothioate-protected probes resulted in variable uptake of 3H-thymidine, demonstrating that these probes, unlike the phosphodiester probes, have non-specific effects on cells. Addition of synthetic CRH to the cells incubated with the antisense phosphodiester probe partially restored the proliferative response of splenocytes to Con A. Immunoreactive (ir) CRH measured by radioimmunoassay in splenocytes incubated with the antisense probe was significantly less than ir-CRH in splenocytes incubated with the nonsense probe or without probe, indicating that the expression of splenic CRH mRNA was specifically impaired. This attenuation of the cell proliferative response following reduced expression of splenic ir-CRH provides functional evidence for the involvement of endogenously synthesised immune ir-CRH in splenocyte activation.

Animals↗
PubMed1997

Differential regulation of hypothalamic pituitary corticotropin releasing hormone receptors during development of adjuvant-induced arthritis in the rat.

The expression of corticotropin releasing hormone (CRH) in the hypothalamic paraventricular nucleus (PVN) and CRH receptor mRNA in the PVN and anterior pituitary was studied during development of adjuvant-induced arthritis in Piebald-Viral-Glaxo rats, using in situ hybridization techniques. As previously shown with i.p. hypertonic saline injection, basal and immobilization stress-stimulated CRH mRNA levels in the PVN were significantly lower than in controls 14 days after adjuvant injection. However, 7 days after injection, preceding the onset of inflammation, the increase of CRH mRNA following immobilization was significantly higher than in control rats. In contrast to other chronic stress paradigms, inflammation stress failed to induce type-1 CRH receptor (CRH-R1) mRNA in the PVN, either at 7 days, or at 14 days after adjuvant injection, when inflammation is present. The ability of acute immobilization to induce CRH-R1 mRNA in the PVN was not affected 14 days after adjuvant injection but parallel to the CRH peptide mRNA response it was markedly potentiated at 7 days. Pro-opiomelanocorpin (POMC) mRNA levels in the anterior pituitary increased significantly 14 days after adjuvant injection, and they were unaffected by 1 h immobilization. While CRH binding in the pituitary decreased significantly 14 days after adjuvant injection, CRH-R1 mRNA was unchanged. This study shows biphasic hypothalamic responses to acute stress during development of adjuvant-induced arthritis, with enhanced CRH peptide and CRH-R1 mRNAs responses at 7 days, preceding the onset of inflammation, and blunted CRH mRNA responses at 14 days at the height of the inflammatory response. The lack of CRH receptor expression in the PVN in this model of chronic inflammation stress associated to low hypothalamic CRH peptide levels supports the view that positive feedback regulation by CRH is necessary to maintain enhanced CRH expression during chronic stress.

Animals↗
PubMed1996

The role of endogenous serotonin in adjuvant-induced arthritis in the rat.

We have investigated the effects of serotonin depletion on the progress and severity of adjuvant-induced arthritis in the Piebald-Viral-Glaxo (PVG) strain of rat. Total body depletion of serotonin was achieved using p-chlorophenylalanine given i.p. Two paradigms were investigated. First we depleted serotonin at the time of injection of the adjuvant to determine whether serotonin was involved in the initial induction phase. Secondly, we depleted serotonin at the time of onset of the inflammation. Serotonin levels in the hypothalamic paraventricular nucleus (PVN) were reduced by > 95%. Depletion at the time of induction had no effect on the severity of the disease (determined by the increase (determined by the increase in hind paw volume) 14 days after injection of the adjuvant. In contrast, depletion at the time of onset of the disease resulted in a significant reduction in severity at day 14, suggesting a pro-inflammatory role for serotonin in this model. The decrease in corticotrophin-releasing factor (CRF) mRNA in the PVN associated with the development of adjuvant arthritis in PVG rat was reversed in the serotonin-depleted animals. Central serotonin could be one of the factors responsible for the reduced expression of CRF mRNA in response to adjuvant-induced arthritis in this rat strain. These data suggest that serotonin antagonists may be efficacious in reducing the severity of acute inflammatory episodes.

Animals↗
PubMed1995

Endogenous substance P inhibits the expression of corticotropin-releasing hormone during a chronic inflammatory stress.

We have investigated the effects of a chronic inflammatory stress on substance P (SP) levels in the hypothalami of rats given adjuvant-induced arthritis (AA). Fourteen days after injection of Mycobacterium butyricum, substance P concentrations in the paraventricular nucleus (PVN) and median eminence/arcuate nucleus were significantly increased. In AA rats injected intraperitoneally with the specific neurokinin-1 receptor antagonist RP67580, plasma ACTH and corticosterone concentrations were significantly elevated, and corticotropin-releasing hormone (CRH) mRNA in the PVN was increased compared to the AA group which received saline alone. The increases in hypothalamic SP in AA, together with the data demonstrating that HPA axis activity is enhanced in AA following injection of a SP antagonist, are consistent with the hypothesis that SP is acting as an inhibitor of CRH expression in this model of chronic inflammatory stress.

Adrenocorticotropic Hormone↗
PubMed1995

Changes in ACTH and beta-endorphin immunoreactivity in immune tissues during a chronic inflammatory stress are not correlated with changes in corticotropin-releasing hormone and arginine vasopressin.

We have previously demonstrated that the chronic inflammatory stress of adjuvant-induced arthritis in rats can alter levels of the neuropeptides adrenocorticotropin (ACTH), beta-endorphin, arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) in tissues of the immune system. We now present data showing that the patterns of these changes in the spleens and thymuses of Piebald-Viral-Glaxo rats are quite dissimilar throughout the course of the disease. Immunoreactive (ir)-CRH, AVP, ACTH and beta-endorphin were measured by radioimmunoassays in spleen and thymic extracts taken at days 3, 7, 11 and 14 following injection of adjuvant. AVP was increased in the spleen at day 14 compared to the controls (79.4 +/- 4.4 and 60.0 +/- 9.0 fmol/g tissue respectively), but no change occurred in the thymus. CRH contents were increased in the spleen at day 14 (33.4 +/- 3.5) compared to controls (22.1 +/- 2.4 fmol/g tissue), and in the thymus at day 11 (24.0 +/- 2.3) compared to controls (14.1 +/- 2.5 fmol/g tissue). Increases in ACTH content were observed in spleens from arthritic rats at days 3 (365 +/- 23), 11 (359 +/- 32) and 14 (355 +/- 45 fmol/g tissue) compared to controls (198 +/- 37 fmol/g tissue). In the thymus, however, ACTH was elevated only at day 14. Beta-Endorphin levels in the spleen were elevated only at day 14 (289 +/- 41) compared to controls (97 /+- 22 fmol/g tissue).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1995

A protective role for testosterone in adjuvant-induced arthritis.

We have investigated the role of the gonadal steroids testosterone (T) and progesterone in modulating: (1) the onset and severity of adjuvant-induced arthritis (AA), (2) the response of the hypothalamo-pituitary-adrenal (HPA) axis, and (3) the levels of plasma prolactin and anterior pituitary prolactin messenger ribonucleic acid (mRNA) in the rat. Male rats were castrated (CSX) and received either no T, low T or high T delivered using silastic implants. In a second study experimental groups comprised CSX/AA, CSX/AA + progesterone or CSX/AA + progesterone + T. The time of onset was sooner and the severity of AA was greater in CSX rats. Inflammation was prevented by T replacement. Endogenous plasma T levels were decreased in AA rats. In control animals with AA there was an increase in pro-opiomelanocortin (POMC) mRNA in the anterior pituitary and of plasma corticosterone, and a decrease in corticotrophin-releasing factor (CRF) mRNA. These changes in the HPA axis of AA and CSX/AA rats were reversed by T replacement. These data suggest that T has an important protective effect on the progress and severity of AA. This was reflected by a reversal of the neuroendocrine changes of the HPA axis. Progesterone treatment alone had no effect on the severity of the disease. Prolactin mRNA in the anterior pituitary was decreased in the CSX and in the CSX/AA group but was not altered by AA. Plasma prolactin was raised in AA but T replacement did not reduce these elevated levels despite the absence of disease. Thus, prolactin provides a poor indicator of inflammation, suggesting that it may not be a potent pro-inflammatory compound in AA.

Analysis of Variance↗
PubMed1995

Evidence for arginine vasopressin as the primary activator of the HPA axis during adjuvant-induced arthritis.

1. Adjuvant-induced arthritis (AA) is an experimental inflammation of the joints that results in chronic activation of the hypothalamo-pituitary-adrenal (HPA) axis. 2. In this study the role of hypothalamic corticotrophin-releasing factor (CRF) and arginine vasopressin (AVP) in the regulation of the HPA axis in this condition both in Sprague-Dawley (SD), and Piebald-Viral-Glaxo (PVG) rats has been further characterized. 3. The increase in AVP peptide content of portal blood (as early as day 11), just prior to the onset of arthritis is confirmed and further increases, peaking at day 16 are shown, coincident with the progression of inflammation in the PVG rats. 4. The increase in AVP is associated with a significant increase in the expression of AVP but not CRF mRNAs in the medial parvocellular division of the hypothalamic paraventricular nucleus (PVN) of arthritic SD rats. 5. In the presence of maximal inflammation of SD rats there was a significant decrease in the maximum binding of [125I]-Tyr-oCRF to anterior pituitary membranes, whereas AVP receptor concentration in anterior pituitary membranes from both PVG and SD rats showed a significant increase with respect to controls. 6. The basal adrenocorticotrophin (ACTH) secretion in vitro was similar in both control and arthritic SD rats but that from arthritic PVG rat pituitaries was significantly greater than the respective controls (436 +/- 91 v 167 +/- 23 pg/tube). The ACTH response of pituitaries of arthritic PVG rats to CRF or the combination of CRF and AVP was significantly higher compared with the controls, although the ACTH response of arthritic SD rat pituitaries was unchanged. 7. The results are consistent with the view that activation of the parvocellular vasopressin system has an important role in the adaptation of the HPA axis to experimentally-induced chronic stress of arthritis.

Adrenocorticotropic Hormone↗
PubMed1994

The effects of restraint or hypertonic saline stress on corticotrophin-releasing factor, arginine vasopressin, and proenkephalin A mRNAs in the CFY, Sprague-Dawley and Wistar strains of rat.

It is generally assumed that the stress response of different strains of rat will be identical following exposure to acute stress. In the present study we have examined the activation of the hypothalamo-pituitary-adrenal axis in the Wistar, Sprague-Dawley and CFY strains of rat following exposure to either the predominantly psychological stress of restraint or the physical stress of i.p. hypertonic saline injection. We have investigated the hypothalamic activation of corticotrophin-releasing factor (CRF) and proenkephalin A (PEA) mRNAs in the parvocellular cells of the paraventricular nucleus (PVN) and arginine vasopressin (AVP) in both the magnocellular and parvocellular regions in the PVN following acute stress. In addition we have measured corticosterone as an index of end-point activation. Circulating corticosterone and CRF mRNA were increased in all three strains following either stress. AVP and PEA mRNAs were increased following hypertonic saline but only in the CFY strain following restraint. Overall the relative increase in the parameters measured was greater in the CFY strain of rat than the other strains. These data demonstrate marked differences in response to acute stress in the three strains of rat examined. These varying responses must be taken into consideration when designing or interpreting any study investigating the stress response.

Animals↗
PubMed1994

Contents of corticotropin-releasing hormone and arginine vasopressin immunoreactivity in the spleen and thymus during a chronic inflammatory stress.

We have previously found that proopiomelanocortin (POMC) mRNA and levels of adrenocorticotropin (ACTH) and beta-endorphin peptides are increased in the spleen and thymus of rats with adjuvant-induced arthritis (AA), and immunologically mediated inflammatory disease. To determine whether alterations in immune tissue POMC during AA are also accompanied by changes in immune tissue corticotropin-releasing hormone immunoreactivity (ir-CHR) and arginine vasopressin (AVP), we measured ir-CRH and AVP by radioimmunoassays in spleen and thymic extracts 14 days following injection of adjuvant. Ir-CRH was detectable in all extracts of spleen and thymus. Total contents of ir-CRH in the spleen and thymus were not altered following arthritis, although a significant decrease was observed in splenic extracts from arthritis rats (40.0 +/- 4.2 fmol/g tissue) compared to controls (69.5 +/- 8.4 fmol/g tissue) when contents were expressed as amount per weight of tissue. Low levels of AVP were also detected in immune tissues, with contents significantly increased in spleens from arthritis animals (17.4 +/- 1.6 fmol/g tissue) compared to controls (10.6 +/- 1.9 fmol/g) but thymic contents of AVP were not altered by arthritis (10.6 +/- 1.3 fmol/g) compared to controls (9.2 +/- 0.7 fmol/g). Control levels of AVP were significantly higher in spleens and thymuses from female rats (53 +/- 5 and 25 +/- 4 fmol/g tissue, respectively) compared to males. G-50 chromatography revealed that the principal form of splenic ir-CRH is CRH(1-41), although in non-arthritic animals some ir-CHR eluted in a position indicating a slightly larger form.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Role of central catecholamines in the modulation of corticotrophin-releasing factor mRNA during adjuvant-induced arthritis in the rat.

The development of adjuvant-induced arthritis in the rat is associated with an activation of the hypothalamo-pituitary-adrenal axis. In the Piebald-Viral-Glaxo strain of rat there is however a paradoxical decrease in corticotrophin-releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus (PVN) and a decrease in CRF-41 peptide release into the hypophysial portal blood with increasing severity of disease. In the present study we have investigated the role of endogenous catecholamines within the PVN as possible inhibitory factors acting on CRF neurons during adjuvant-induced arthritis. Noradrenaline (NA) concentrations were approximately doubled in the PVN of arthritic animals. Depletion of endogenous catecholamines following direct 6-OHDA lesions of the PVN resulted in a significant depletion in PVN NA. The increase in NA observed in arthritic animals appears to have a protective role since depletion of NA increased the severity of the disease. Neither the increase in circulating levels of corticosterone nor the decrease in CRF mRNA in the PVN were prevented following NA depletion. Our results suggest that modification of central neurotransmitter systems are able to influence the severity of adjuvant-induced arthritis.

Animals↗
PubMed1994

An investigation of the effects of interleukin-1 beta on plasma arginine vasopressin in the rat: role of adrenal steroids.

While the effects of cytokines on the hypothalamo-pituitary-adrenal axis have received a great deal of attention in recent years the effects of cytokines on posterior pituitary hormone release has been less well characterized. In the present study we have investigated the effects of a single i.p. injection of interleukin (IL)-1 beta on circulating levels of vasopressin (AVP) in the rat. We have found that the ability of IL-1 beta to increase plasma AVP is strongly influenced by circulating levels of glucocorticoid steroids. IL-1 beta did not affect plasma AVP in sham-operated control animals over the 4 h period of study. In contrast, following adrenalectomy we were able to stimulate AVP substantially with increases over the 4 h period. This effect was reduced by treatment of adrenalectomized rats with a low dose of dexamethasone and abolished with a high dose. These data suggest an inverse relationship between circulating levels of glucocorticoids and the ability of IL-1 beta to stimulate plasma AVP.

Adrenalectomy↗
PubMed1993

Stress-induced activation of CRF and c-fos mRNAs in the paraventricular nucleus are not affected by serotonin depletion.

The role of serotonin in regulating the stress response is controversial. We have investigated the effects of serotonin depletion by p-chlorophenyl-alanine (PCPA) on corticotrophin-releasing factor (CRF) mRNA and c-fos mRNA responses in the paraventricular nucleus (PVN) together with circulating levels of ACTH and corticosterone to both physical and psychological stressors in the rat. PCPA pretreatment, which resulted in a 95% depletion in hypothalamic serotonin, had no effect on basal levels of ACTH or the increase in response to the physical stress of hypertonic saline. Plasma ACTH concentrations were also not affected by serotonin depletion in response to the predominantly psychological stress of restraint. Both basal and restraint stress-induced circulating corticosterone levels were however further stimulated in the PCPA-pretreated rats suggesting a possible inhibitory serotoninergic tone at the adrenal level. C-fos mRNA was undetectable in control animals. Activation of c-fos mRNA in response to stress was unaffected by serotonin depletion and the activation of magnocellular PVN and supraoptic nucleus cells was demonstrated to be stressor dependent. Basal and stress-induced levels of CRF mRNA were unaffected by PCPA pretreatment. It appears therefore that under these experimental conditions there is little if any involvement of serotonin in either basal levels or the stress-induced activation of the hypothalamo-pituitary-adrenal axis in vivo.

Adrenocorticotropic Hormone↗
PubMed1993

Expression of corticotropin-releasing factor mRNA in response to stress.

The corticotropin-releasing factor (CRF)-containing neurons of the parvocellular division of the hypothalamic paraventricular nucleus play a pivotal role in the regulation of the hypothalamo-pituitary-adrenal axis. We have studied the regulation of these neurons in the conscious rat using the technique of quantitative in situ hybridization histochemistry. Corticosteroid feedback reduces CRF mRNA levels in a dose-dependent manner, although even prolonged administration of very high doses cannot abolish CRF transcripts completely. Both physical and psychological stressors produce a robust and readily reproducible increase in CRF mRNA. These responses cannot be prevented by changes in circulating corticosteroids--a similar magnitude of response occurs with high basal levels in the adrenalectomized animal and with low basal levels during treatment with supraphysiological doses of glucocorticoid. Alterations in CRF mRNA levels in response to stress are, however, lost during the physiological condition of lactation, a state known to result in stress hyporesponsiveness, and also after 6-hydroxydopamine lesions to the catecholaminergic innervation of the paraventricular nucleus. We have also studied two conditions of chronic immunological activation of the hypothalamo-pituitary-adrenal axis--adjuvant-induced arthritis and experimental allergic encephalomyelitis. Both of these results in activation of the hypothalamo-pituitary-adrenal axis with increased plasma corticosterone and ACTH, and pituitary pro-opiomelanocortin (POMC) mRNA. Unexpectedly, however, the activation of pituitary corticotrophs does not seem to be a primary result of increased activation of the CRF neurons, which actually show a consistent fall in CRF mRNA.

Acute Disease↗
PubMed1993

Effect of adrenalectomy and stress on interleukin-1 beta-mediated activation of hypothalamic corticotropin-releasing factor mRNA.

We have investigated the effect of (a) stress and (b) steroid feed-back on the interleukin-1 beta (IL-1 beta)-mediated increase of corticotropin-releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus. Both IL-1 beta and stress resulted in increased levels of CRF mRNA and when both were given together, the combination resulted in an additive effect on the increase in CRF transcripts. The effect of IL-1 beta was blunted by adrenalectomy, but returned when a replacement dose of dexamethasone was administered. The IL-1 beta-induced increase in CRF mRNA is dependent on the presence of circulating glucocorticoids, and its mechanism of action on CRF mRNA appears to be distinct from that activated in response to stress.

Adrenalectomy↗
PubMed1993

Changes in hypothalamic corticotrophin-releasing factor and anterior pituitary pro-opiomelanocortin mRNA during the course of experimental allergic encephalomyelitis.

The pituitary-adrenal axis is activated during the course of experimental allergic encephalomyelitis (EAE), a paralytic disease resulting from an immunological reaction against central nervous system myelin. The magnitude of the adrenal response not only correlates with the severity of disease, but also serves an important functional role in recovery. We have shown that in EAE there are short-term changes in anterior pituitary pro-opiomelanocortin (POMC) mRNA as well as plasma corticosterone which can be detected before the development of clinical disease. At peak clinical signs when corticosterone and POMC mRNA are maximal, hypothalamic corticotrophin-releasing factor (CRF) mRNA is suppressed, suggesting that pituitary-adrenal activation is not mediated by CRF. Following recovery all parameters return to normal.

Animals↗
PubMed1993

HPA axis responses to acute stress and adrenalectomy during adjuvant-induced arthritis in the rat.

Adjuvant-induced arthritis results in chronic activation of the hypothalamo-pituitary-adrenal (HPA) axis. In the Piebald-Viral-Glaxo (PVG) rat, however, corticotropin-releasing factor (CRF) mRNA in the parvocellular paraventricular nucleus (pPVN) of the hypothalamus was reduced, and the normal corticosterone and CRF mRNA responses to acute stress were inhibited. The proenkephalin A mRNA response to stress in the pPVN was maintained, implying a specific inhibition of the CRF mRNA responses in this pathological situation. Adrenalectomy at day 0 (the time of adjuvant injection), day 13 (just before inflammation), or day 19 (submaximal inflammation) resulted in a marked increase in CRF mRNA compared with day 21 adrenal-intact arthritic animals. However, levels were below those of nonarthritic adrenalectomized rats, demonstrating that the inhibition of CRF mRNA associated with arthritis is not simply due to changes in glucocorticoid feedback. Proopiomelanocortin mRNA in the anterior pituitary was markedly increased in all adrenalectomized arthritic animals above the increase seen in sham-adrenalectomized day-21 arthritic rats. Adrenalectomy was always associated with an increase in the severity of the disease.

Acute Disease↗