Neuroendocrine immunology: relevance to the management of critical illness.
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Critical Illness↗
Biomedical subjects
J W Holaday
Publications and source records attributed to J W Holaday.
Interaction of beta-funaltrexamine with [3H]cycloFOXY binding in rat brain: further evidence that beta-FNA alkylates the opioid receptor complex.
beta-Funaltrexamine (beta-FNA) is an alkylating derivative of naltrexone. In addition to acting as an irreversible inhibitor of mu-receptor-mediated physiological effects, intracerebroventricular (i.c.v.) administration of beta-FNA to rat attenuates the ability of selective delta receptor antagonists and naloxone to reverse delta receptor-mediated effects. Moreover, recent work demonstrated that i.c.v. administration of beta-FNA alters the conformation of the opioid receptor complex, as inferred by a decrease in the Bmax of the lower affinity [3H][D-ala2,D-leu5]enkephalin binding site. Consistent with the decreased potency of naloxone as an inhibitor of delta receptor mediated effects, beta-FNA doubled the naloxone IC50 for displacing [3H][D-ala2,D-leu5]enkephalin from its lower affinity binding site. These data collectively support the hypothesis that the opioid receptor complex postulated to mediate mu-delta interactions in vivo is identical to the opioid receptor complex as defined by vitro ligand binding studies. A direct prediction of this hypothesis is that beta-FNA should increase the Kd of antagonists for the mu binding site (mu cx) of the receptor complex. The data reported in this paper demonstrate that beta-FNA doubled the IC50 of the potent narcotic antagonist, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY) for displacing [3H][D-ala2,D-leu5]enkephalin from its lower affinity binding site, and doubled the Kd of [3H]cycloFOXY for its mu binding site, providing additional data that the mu binding site labeled by [3H]cycloFOXY is the mu binding site of the opioid receptor complex. beta-FNA also altered the kappa binding site labeled by [3H]cycloFOXY, and when administered intrathecally to mice, beta-FNA produced a longlasting antinociception in the acetic acid writhing test.
Alkylating Agents↗
Role of adrenal cortical activation in the immunosuppressive effects of chronic morphine treatment.
Implantation of a 75-mg morphine pellet in sham-adrenalectomized male C3H/HeN mice resulted in significant elevations of serum corticosterone levels within 6 h. Corticosterone levels remained elevated (3- to 4-fold) for 72 h and had returned to normal by 120 h postimplantation. Within 48 h of pellet implantation, morphine-pelleted mice exhibited marked reductions in spleen (35%) and thymus weight (56%) relative to values in placebo-pelleted controls. In addition, adrenal hypertrophy was observed in the morphine-pelleted shams (50% increase in adrenal weight relative to placebo. The magnitude of splenic and thymic atrophy was reduced by about 50% in adrenalectomized morphine-pelleted mice (17% and 22% reductions, respectively) compared to that in adrenalectomized mice implanted with placebo pellets. Lymphocyte proliferative responses to the T-cell mitogen Concanavalin-A and the B-cell mitogen bacterial lipopolysaccharide were also significantly reduced in the morphine-pelleted sham mice. Morphine-induced suppression of Concanavalin-A- or lipopolysaccharide-stimulated lymphocyte proliferation was absent in adrenalectomized mice. Effects similar to adrenalectomy (e.g. lessening of magnitude of morphine-induced suppression of lymphoid organ weight and lymphocyte proliferation) were found in morphine-pelleted mice given the glucocorticoid receptor antagonist RU-486 at a dose of 10 mg/kg, twice daily. These studies imply that morphine-induced immunosuppression is at least in part mediated by the increase in serum corticosterone levels after implantation of the morphine pellet.
Adrenal Cortex↗
Neuroendocrine-immune interactions and their relevance to the pharmacology of critical care medicine.
Many clinical conditions and the drug used to treat them are characterized by derangements of the brain/endocrine/immune axis. Drugs commonly used in the ICU have previously unrecognized effects on the immune system; these drugs (including steroid hormones, dopamine agonists, metoclopramide, haloperidol, morphine, mucolytics, cyclosporine and other pharmacologic agents) affect the release of hormones that, in turn, modulate immune function. This article will summarize some important functional interactions among the brain and the endocrine and immune systems, with particular relevance to the practice of critical care medicine. Evidence will be presented to demonstrate that the immunosuppressive effects of hypoprolactinemia, chronic morphine treatment and chronic glucocorticoid administration are reversed by prolactin or by drugs that stimulate endogenous prolactin release. Furthermore, prolactin, synthesized by lymphocytes, plays an autocrine role in their proliferation.
Critical Care↗
Evaluation of thyrotropin releasing hormone as a therapeutic intervention for endotoxemia.
Thyrotropin releasing hormone (TRH) has been reported to reduce endotoxin-induced hypotension and mortality rate in conscious rats. Limited data are available to explain these effects. We evaluated hemodynamic parameters, metabolic function, tissue injury, and survival rate in three groups of instrumented conscious rats following intravenous endotoxin (20 mg/kg, LD/90-24 h) challenge. Pretreatment with TRH (2.0 mg/kg, i.v.) was administered 10 min before endotoxin (n = 10) and control (n = 10) animals were given an equivalent volume of saline. The post-treated group (n = 7) was given TRH at the nadir of the hypotensive response following endotoxin to duplicate published protocols. 5 min after endotoxin blood pressure and cardiac output were significantly higher in the post and pre-treatment groups, respectively, compared to the untreated group. There were no differences at other times. Systemic vascular resistance was not affected by either treatment mode at any time. TRH treatment following endotoxin resulted in transient increases in heart and respiration rates and decreased central venous pressure during the first 30 min. Metabolic function indicated by measurements of glucose, lactate, hematocrit, pH, PO2, and PCO2 at 60 and 240 min after endotoxin was not modified by TRH. The hemorrhagic small intestine characteristic of this model was not improved by either treatment mode. Mortality rates at 4 h after endotoxin were 20% for the untreated, 40% for the pre-treated, and 43% for the post-treated. These results suggest TRH exerts early transient effects on cardiovascular responses evoked by endotoxin in the conscious rat but no lasting beneficial effects were found to support the use of TRH as a mono-therapy for endotoxemia.
Animals↗
Effects of NMDA receptor antagonists following spinal ischemia in the rabbit.
Evidence has accumulated to implicate the excitatory amino acid neurotransmitters, glutamate and aspartate, in the pathophysiology of central nervous system (CNS) ischemic injury. It appears from both in vivo and in vitro experiments that they exert their excitotoxic effects in CNS ischemia by their actions at the N-methyl-D-aspartate (NMDA) receptor complex. In the present study, we examined the effects of MK-801 and ketamine, two noncompetitive NMDA receptor antagonists, in a model of spinal cord ischemia in conscious rabbits produced by occluding the infrarenal aorta for 25 min. Five minutes after reperfusion, animals were treated with either saline, ketamine, or MK-801. By 6 h postreperfusion, all treatment groups exhibited an initial recovery of hindlimb motor function, after which the saline- and ketamine-treated groups had a similar progressive deterioration in function over the next 48 h. However, the MK-801-treated rabbits continued to recover motor function such that neurological scores in these rabbits were significantly improved relative to those of the saline-treated animals at 48 h. Histopathological evaluation showed that MK-801-treated rabbits tended to have a lesser degree of central gray matter necrosis. These results indicate that MK-801 protected against the secondary deterioration associated with this model and strengthen the potential therapeutic use of NMDA receptor antagonists in the treatment of CNS ischemia.
Animals↗
Pretreatment of rats with the irreversible mu-receptor antagonist, beta-FNA, fails to prevent naltrexone-induced upregulation of mu-opioid receptors.
This study examined the effect of beta-funaltrexamine (beta-FNA), an irreversible mu-receptor antagonist, on naltrexone-induced upregulation of mu-(mu cx + mu nex) and delta nex-opioid receptors. [The subscripts 'cx' and 'nex' denote binding sites 'in' (cx) and 'not in' (nex) the opioid receptor complex.] Rats were treated according to the following protocol. Two naltrexone or two placebo pellets were implanted subcutaneously in a nylon mesh on day 1. and were removed intact on day 8. Rats were given either saline or 20 nmol of beta-FNA in 10 microliters of saline (i.c.v.) on days 1, 3, 5 and 6, 60 min prior to implantation of the pellet. On day 9 frozen lysed-P2 membranes were prepared for assay of mu binding sites. In other experiments, membranes were depleted of mu-receptors by pretreatment with the site-directed acylating agent 2-(4-ethoxybenzyl)-l-diethylaminoethyl-5-isothiocyanatobenzimid azole.HCl (BIT) for assay of delta nex binding sites, using [3H] [D-ala2, D-leu5]enkephalin. The results demonstrated that beta-FNA did not upregulate the mu binding sites and also did not prevent naltrexone-induced upregulation of mu binding sites. Both beta-FNA and naltrexone increased the Bmax of delta nex binding sites and their effects were additive. These data suggest that the mechanism(s) responsible for antagonist-induced upregulation of opioid receptors are more complex than previously appreciated.
Animals↗
Immunomodulatory effects of chronic morphine treatment: pharmacologic and mechanistic studies.
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Animals↗
Chronic administration of morphine and naltrexone up-regulate mu-opioid binding sites labeled by [3H][D-Ala2,MePhe4,Gly-ol5]enkephalin: further evidence for two mu-binding sites.
A variety of data support the hypothesis of an opiate receptor complex composed of distinct, yet interacting mu and delta binding sites (termed mu cx and delta cx to indicate binding sites 'in the complex'), in addition to independent mu and delta binding sites, termed mu ncx and delta ncx, to indicate binding sites 'not in the complex'. Ligand binding studies using membranes and slide-mounted sections of rat brain support the hypothesis that the irreversible mu-antagonist beta-funaltrexamine (FNA) selectively alkylates the opiate receptor complex, altering the binding of mu agonists to the mu cx binding site and the binding of [3H][D-Ala2,D-Leu5]enkephalin to the delta cx site. Previous studies demonstrated that the chronic administration of morphine to rats selectively 'upregulates' the opiate receptor complex. In contrast, the chronic administration of naltrexone upregulates several types of opioid receptors, including kappa, the delta ncx binding site, and multiple binding sites labeled by mu agonists. A prediction based upon these observations is that, using [3H][D-Ala2,MePhe4,Gly-ol5]enkephalin to label mu binding sites, chronic morphine should upregulate only the mu cx binding site, whereas chronic naltrexone should additionally up-regulate the mu ncx binding site. In this study we test and confirm this hypothesis, using sensitivity to FNA to define the mu cx binding site. The implications of these data for models of the opioid receptors and the mechanism(s) of tolerance and dependence are discussed.
Animals↗
Rapid release of multiple hormones from rat pituitaries perifused with recombinant interleukin-1.
Previous studies demonstrated a direct action of interleukin-1 (IL-1) on release of hormones from rat anterior pituitary cells in monolayer culture. To rule out any possibility of a paracrine effect from the elevated hormones in the static monolayer system, and to examine further the dynamics of hormone release elicited by IL-1, studies were conducted with rat anterior pituitary tissue in a computer-controlled automated perifusion system. In experiments performed on the same day as sacrifice, IL-1 stimulated the release of adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), thyroid stimulating hormone (TSH), growth hormone (GH) and prolactin (PRL) in a dose-related manner. Peak levels were achieved within 6 minutes of exposure to IL-1. However, PRL was not increased over the baseline fluctuations when pituitaries were perifused with IL-1 after 72 hours of incubation. Hormone release did not appear to undergo desensitization after multiple short pulses of IL-1. Heat-denatured IL-1 had no effect on hormone release. The rapid response suggests that IL-1 acts acutely to release preformed hormone stores.
Animals↗
Selective kappa antagonist properties of nor-binaltorphimine in the rat MES seizure model.
The opioid antagonist properties of nor-binaltorphimine (nor-BNI; 17,17'-Bis(cyclopropylmethyl)-6,6',7,7'-tetradehydro-4,5:4', 5'-diepoxy-6,6'-(imino) [7,7'-bimorphinan]-3,3',14,14'-tetrol) were evaluated in vivo in the rat maximal electroshock (MES) seizure model. Following s.c. or i.c.v. pretreatment, nor-BNI selectively antagonized the anticonvulsant effects of the kappa opioid U50, 488, significantly increasing its ED50 by 2.3 and 4.5 fold, respectively. In contrast, pretreatment with nor-BNI (s.c. or i.c.v.) failed to antagonize the anticonvulsant effects of the selective mu opioid, DAMGO. At the doses and injection routes used, nor-BNI itself had no apparent effect on overt behavior or MES-induced convulsions. These data support the earlier suggestion that the anticonvulsant effects of U50,488 are mediated by kappa opioid receptors and confirm 1) the selectivity of nor-BNI as a kappa antagonist and 2) its applicability as a pharmacological tool in the differentiation of multiple opioid receptors.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
A study of the interaction of the alkylating agent, NIH10236, with opioid receptors in vitro and in vivo.
The series of experiments reported in this paper examined the spectrum of subtypes of opioid receptors alkylated in vitro by N-cyclopropylmethyl-7 alpha-methylfumaramido-6,14- endoethenotetrahydronororipavine (NIH10236) and four optical isomers of the methylfumaramidophenethyl derivatives of 3-methylfentanyl. Pretreatment of membranes with NIH10236 resulted in a wash-resistant inhibition of the binding of [3H]6 beta-fluoro-6-desoxyoxymorphone (mu binding sites), the binding of [3H][D-ala2,D-leu5]-enkephalin (both the higher and lower affinity delta binding sites) and was without effect on kappa binding sites labelled with [3H]bremazocine. All four potential alkylating derivatives of 3-methylfentanyl were inactive. Pretreatment of membranes with 1 microM of the reversible ligands, (+)-cis-3-methylfentanyl, but not its enantiomer, inhibited the binding of [3H]6 beta-fluoro-6-desoxyoxymorphone and the binding of [3H][D-ala2,D-leu5]enkephalin to the lower affinity binding sites by over 90%. This phenomenon is termed "pseudo-irreversible inhibition." Incubation of pretreated membranes for 60 min at 37 degrees C, in the presence of 200 mM NaCl and 50 microM GppNHp, only partially reversed the masking of opioid receptors by (+)-cis-3-methylfentanyl. For in vivo experiments, membranes were prepared 18-24 hr after the intracerebroventricular administration of 80 and 50 micrograms of NIH10236. This resulted in decreased labelling of mu binding sites, lower affinity [3H][D-ala2,D-leu5]enkephalin binding sites, as well as kappa binding sites, labelled by [3H]U69,593 and [3H]bremazocine. There was no apparent alteration in the higher affinity [3H][D-ala2,D-leu5]enkephalin binding site.(ABSTRACT TRUNCATED AT 250 WORDS)
Alkylating Agents↗
Respiratory and cardiovascular effects of thyrotropin-releasing hormone as modified by isoflurane, enflurane, pentobarbital and ketamine.
Thyrotropin-releasing hormone (TRH) possesses significant arousing and cardio-respiratory stimulant actions. The effects of a 2 mg/kg i.v. bolus dose of TRH on respiration and systemic hemodynamics were compared in conscious, freely-moving rats and during anesthesia with 4 different anesthetics. Fifty-four male Sprague-Dawley rats weighing 285 +/- 4 g (mean +/- S.E.M.) were divided into 5 groups: conscious, enflurane (2%), isoflurane (1.4%), pentobarbital (8 mg/kg/h i.v.), and ketamine (60 mg/kg/h i.v.). Anesthetized rats were intubated and breathed oxygen or anesthetic/oxygen spontaneously. Aortic blood pressure, heart rate, cardiac output, respiratory rate, arterial blood pH, blood gases, lactate and glucose were measured, and data were collected over a 20 min baseline period and for 130 min post-TRH. TRH increased respiratory rate in all groups; concomitant changes in arterial PCO2 indicated increased minute ventilation in the inhalation agent groups but not in the i.v. anesthetic groups or in the awake group. Significant respiratory depression in the enflurane group was rapidly reversed by TRH. The respiratory stimulant and arousing effects of TRH were smallest with ketamine anesthesia. The hemodynamic responses to TRH were consistent with a pattern of sympathoadrenalmedullary activation and were relatively uniform across groups despite anesthetic-induced alterations in baseline values. TRH or its analogues may prove useful as an analeptic in clinical anesthesia.
Animals↗
The therapeutic efficacy of opiate antagonists in hemorrhagic shock.
The endogenous opioids have been implicated as contributing factors to the cardiovascular dysfunction of shock. Opiate receptor antagonists improve cardiovascular function and long-term survival in laboratory animal models of shock. In this communication, evidence of the therapeutic efficacy of opiate antagonists in canine and primate hemorrhagic shock is presented. The animals were hemorrhaged into a reservoir to lower MAP to 45 mmHg and that pressure was maintained for 1 h at which time the reservoir was clamped and treatment initiated. The "shed blood" was returned at t = 120 min and treatment continued until t = 180 min. Opiate antagonists employed included naloxone, naltrexone and the mixed agonist/antagonist agent, nalbuphine. Both naloxone and naltrexone improved cardiac function at doses of 1 and 2 mg/kg. Animal survival was significantly enhanced in the high dose format. Nalbuphine also improved cardiovascular performance at doses from 1 to 4 mg/kg but at higher doses it depressed cardiac performance. The efficacy of the antagonists is attenuated by acidosis and hypothermia. Opiate antagonists may induce cardiac arrhythmias in combination with beta-adrenergic blocking drugs and the efficacy is reduced in animals that received high dose steroid therapy. Thus the use of opiate antagonists would be contraindicated in patients that received drugs such as propranolol or methylprednisolone. There have been no controlled clinical trials of opiate antagonists in human hemorrhagic shock; these are needed for final clarification.
Animals↗
Inhibition of lymphocyte proliferation by antibodies to prolactin.
Recent in vivo studies have shown that treatments that decrease circulating prolactin (PRL) in rodents result in significant immunosuppression. Our attempts to demonstrate corresponding direct stimulatory effects of PRL on cultured lymphocytes were unsuccessful. However, antibodies against pituitary PRL potently inhibited both murine and human lymphocyte proliferation in response to both T and B cell mitogens. Further studies using IL 2 and IL 4 responsive cell lines (CTLL-2 and HT-2) demonstrated that the same anti-PRL antibodies inhibited the proliferative response to these cytokine growth factors. Thus, antibodies to PRL appear to block an event occurring in the G1 to GS phase transition of these cell lines, which constitutively express growth factor receptors. The inhibitory activity of anti-PRL antibodies could be adsorbed by addition of purified human PRL or by immobilized PRL on an affinity column. Antibodies to other pituitary hormones were without inhibitory effect on CTLL-2 cell proliferation. Proliferation of lymphocytes in serum-free medium was also potently inhibited by anti-PRL antibodies, suggesting that antibody effects were not due to neutralization of PRL or other factors contained in culture serum supplements. We suggest from these data that a protein with homology to PRL and recognized by these anti-PRL antibodies is produced by lymphocytes and plays a critical role in their progression through the cell cycle.
Animals↗
Is there a role for naloxone in the treatment of stroke?
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Animals↗
Calcium administration increases the mortality of endotoxic shock in rats.
Calcium chloride is administered frequently to critically ill patients to improve cardiac output and BP. However, Ca has been implicated in the pathophysiology of shock and ischemic disorders. To test the hypothesis that Ca may be deleterious to shock outcome, we studied the effects of CaCl and Ca chelator (EGTA) infusions on mean arterial pressure (MAP) responses to endotoxin and 24-h survival in rats. Increasing ionized Ca from 4.1 +/- 0.06 to 4.9 +/- 0.20 and 8.5 +/- 0.52 mg/dl progressively increased endotoxin lethality from 20% to 37% and 80%, respectively. This occurred despite slight improvements in MAP in hypercalcemic rats. Conversely, hypocalcemia (3.6 +/- 0.08 mg/dl) lowered endotoxin-induced mortality to 0 without significant effects on MAP. Ca and EGTA infusions alone were not associated with any mortality. Although Ca administration may improve MAP, it significantly increases mortality associated with endotoxic shock in rats. Based on these observations, we advise caution when using Ca in patients with sepsis.
Animals↗
Effects of TRH in circulatory shock and central nervous system ischemia.
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Anaphylaxis↗