Emergent immunoregulatory properties of combined glucocorticoid and anti-glucocorticoid steroids in a model of tuberculosis.
In Balb/c mice with pulmonary tuberculosis, there is a switch from a protective Th1-dominated cytokine profile to a non-protective profile with a Th2 component. This switch occurs while the adrenals are undergoing marked hyperplasia. Treatment with the anti-glucocorticoid hormones dehydroepiandrosterone or 3 beta, 17 beta-androstenediol, during the period of adrenal hyperplasia, maintains Th1 dominance and is protective. We investigated the effects of these hormones as therapeutic agents by administering them from day 60, when the switch to the non-protective cytokine profile was already well established. Given at this time (day 60), doses that were protective when given early (from day 0) were rapidly fatal. A physiological dose of the glucocorticoid corticosterone was also rapidly fatal. However when the corticosterone and the anti-glucocorticoid (AED or DHEA) were co-administered, there was protection, with restoration of a Th1-dominated cytokine profile, enhanced DTH responses, and enhanced expression of IL-1 alpha and TNF alpha. Therefore this combination of steroids has an emergent property that is quite unlike that of either type of steroid given alone. It may be possible to exploit the ant-inflammatory properties of glucocorticoids while preserving a Th1 bias, by combining glucocorticoids with DHEA or suitable metabolites. (+info)
Maternal adrenocortical hormones maintain the early development of pancreatic B cells in the fetal rat.
To investigate the effect of maternal adrenocortical hormones on the development of fetal pancreatic islet cells, pregnant rats were adrenalectomised on d 6 of gestation. On d 12-16 the growth patterns of fetal insulin-producing B cells, glucagon-producing A cells, and somatostatin-producing D cells were observed histometrically. Maternal adrenalectomy resulted in growth retardation of fetal B cells on d 12-15. Maternal corticosterone therapy prevented this retardation. Maternal adrenalectomy, however, did not affect the developmental patterns of A and D cells. By Western blotting and immunohistochemistry, glucocorticoid receptors were demonstrated to be present in the islet cells from d 12 to d 15. These results suggest that maternal adrenocortical hormones, glucocorticoids in particular, maintain the early development of fetal pancreatic B cells through their specific intracellular glucocorticoid receptor. (+info)
The Ca2+ channel blockade changes the behavioral and biochemical effects of immobilization stress.
We investigated how the effects of chronic immobilization stress in rats are modified by Ca2+ channel blockade preceding restraint sessions. The application of nifedipine (5 mg/kg) shortly before each of seven daily 2 h restraint sessions prevented the development of sensitized response to amphetamine as well as the stress-induced elevation of the densities of L-type Ca2+ channel in the hippocampus and significantly reduced the elevation of the densities of [3H]nitrendipine binding sites in the cortex and D1 dopamine receptors in the limbic forebrain. Neither stress, nor nifedipine affected the density of alpha 1-adrenoceptors and D1 receptors in the cerebral cortex nor D2 dopamine receptors in the striatum. A single restraint session caused an elevation of blood corticosterone level that remained unaffected by nifedipine pretreatment, but the reduction of this response during the eighth session was significantly less expressed in nifedipine-treated rats. We conclude that L-type calcium channel blockade prevents development of several stress-induced adaptive responses. (+info)
Relationships between environmental organochlorine contaminant residues, plasma corticosterone concentrations, and intermediary metabolic enzyme activities in Great Lakes herring gull embryos.
Experiments were conducted to survey and detect differences in plasma corticosterone concentrations and intermediary metabolic enzyme activities in herring gull (Larus argentatus) embryos environmentally exposed to organochlorine contaminants in ovo. Unincubated fertile herring gull eggs were collected from an Atlantic coast control site and various Great Lakes sites in 1997 and artificially incubated in the laboratory. Liver and/or kidney tissues from approximately half of the late-stage embryos were analyzed for the activities of various intermediary metabolic enzymes known to be regulated, at least in part, by corticosteroids. Basal plasma corticosterone concentrations were determined for the remaining embryos. Yolk sacs were collected from each embryo and a subset was analyzed for organochlorine contaminants. Regression analysis of individual yolk sac organochlorine residue concentrations, or 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs), with individual basal plasma corticosterone concentrations indicated statistically significant inverse relationships for polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs), total polychlorinated biphenyls (PCBs), non-ortho PCBs, and TEQs. Similarly, inverse relationships were observed for the activities of two intermediary metabolic enzymes (phosphoenolpyruvate carboxykinase and malic enzyme) when regressed against PCDDs/PCDFs. Overall, these data suggest that current levels of organochlorine contamination may be affecting the hypothalamo-pituitary-adrenal axis and associated intermediary metabolic pathways in environmentally exposed herring gull embryos in the Great Lakes. (+info)
Increased neurodegeneration during ageing in mice lacking high-affinity nicotine receptors.
We have examined neuroanatomical, biochemical and endocrine parameters and spatial learning in mice lacking the beta2 subunit of the nicotinic acetylcholine receptor (nAChR) during ageing. Aged beta2(-/-) mutant mice showed region-specific alterations in cortical regions, including neocortical hypotrophy, loss of hippocampal pyramidal neurons, astro- and microgliosis and elevation of serum corticosterone levels. Whereas adult mutant and control animals performed well in the Morris maze, 22- to 24-month-old beta2(-/-) mice were significantly impaired in spatial learning. These data show that beta2 subunit-containing nAChRs can contribute to both neuronal survival and maintenance of cognitive performance during ageing. beta2(-/-) mice may thus serve as one possible animal model for some of the cognitive deficits and degenerative processes which take place during physiological ageing and in Alzheimer's disease, particularly those associated with dysfunction of the cholinergic system. (+info)
High-temperature effects on antibody response to viral antigen in mice.
To determine the effects of high-temperature exposure on antibody response to viral antigen in mice, male BALB/c mice were placed for 13 days in animal chambers at 23 degrees C, 32 degrees C, and 35.5 degrees C. Rectal temperature rose from 37 degrees C to 39 degrees C on day 1 in a 35.5 degrees C environment. The rectal temperature was kept constant throughout the exposure period. The IgG-antibody to Sendai virus (SV) antigen was inhibited to about 50% of the control value (23 degrees C). The serum corticosterone concentration indicating thermal stress increased steadily, peaking on day 1 and then gradually decreased and recovered to the normal level on day 13. Body weight decreased to about 72% of the controls on day 13. Thymus and spleen weight decreased to 31.7% and 61.5% respectively. At 32 degrees C, these effects were less than at 35.5 degrees C. Effects of high-temperature exposure at 35.5 degrees C appeared to noticeably decrease thymus and spleen weight. It is clear that IgG-antibody response to SV antigen is suppressed by high-temperature exposure. (+info)
Central administration of rat IL-6 induces HPA activation and fever but not sickness behavior in rats.
Interleukin (IL)-6 has been proposed to mediate several sickness responses, including brain-mediated neuroendocrine, temperature, and behavioral changes. However, the exact mechanisms and sites of action of IL-6 are still poorly understood. In the present study, we describe the effects of central administration of species-homologous recombinant rat IL-6 (rrIL-6) on the induction of hypothalamic-pituitary-adrenal (HPA) activity, fever, social investigatory behavior, and immobility. After intracerebroventricular administration of rrIL-6 (50 or 100 ng/rat), rats demonstrated HPA and febrile responses. In contrast, rrIL-6 alone did not induce changes in social investigatory and locomotor behavior at doses of up to 400 ng/rat. Coadministration of rrIL-6 (100 ng/rat) and rrIL-1beta (40 ng/rat), which alone did not affect the behavioral responses, reduced social investigatory behavior and increased the duration of immobility. Compared with rhIL-6, intracerebroventricular administration of rrIL-6 (100 ng/rat) induced higher HPA responses and early-phase febrile responses. This is consistent with a higher potency of rrIL-6, compared with rhIL-6, in the murine B9 bioassay. We conclude that species-homologous rrIL-6 alone can act in the brain to induce HPA and febrile responses, whereas it only reduces social investigatory behavior and locomotor activity in the presence of IL-1beta. (+info)
Hypertension in mice lacking 11beta-hydroxysteroid dehydrogenase type 2.
Deficiency of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in humans leads to the syndrome of apparent mineralocorticoid excess (SAME), in which cortisol illicitly occupies mineralocorticoid receptors, causing sodium retention, hypokalemia, and hypertension. However, the disorder is usually incompletely corrected by suppression of cortisol, suggesting additional and irreversible changes, perhaps in the kidney. To examine this further, we produced mice with targeted disruption of the 11beta-HSD2 gene. Homozygous mutant mice (11beta-HSD2(-/-)) appear normal at birth, but approximately 50% show motor weakness and die within 48 hours. Both male and female survivors are fertile but exhibit hypokalemia, hypotonic polyuria, and apparent mineralocorticoid activity of corticosterone. Young adult 11beta-HSD2(-/-) mice are markedly hypertensive, with a mean arterial blood pressure of 146 +/- 2 mmHg, compared with 121 +/- 2 mmHg in wild-type controls and 114 +/- 4 mmHg in heterozygotes. The epithelium of the distal tubule of the nephron shows striking hypertrophy and hyperplasia. These histological changes do not readily reverse with mineralocorticoid receptor antagonism in adulthood. Thus, 11beta-HSD2(-/-) mice demonstrate the major features of SAME, providing a unique rodent model to study the molecular mechanisms of kidney resetting leading to hypertension. (+info)