Junichi Fukata

Interleukin-6 stimulates the secretion of adrenocorticotropic hormone in conscious, freely-moving rats.

In order to assess the effect of interleukin-6 on the hypothalamo-pituitary-adrenal axis, we administered recombinant human interleukin-6 to conscious, freely-moving rats. The intravenous injection of interleukin-6 significantly increased the plasma level of adrenocorticotropic hormone 30 min after the injection in a dose-related manner. Immunoneutralization of corticotropin-releasing hormone blocked the stimulatory effects of interleukin-6 on adrenocorticotropic hormone secretion. These observations suggest that interleukin-6 stimulates the secretion of adrenocorticotropic hormone through the corticotropin-releasing hormone and is possibly involved in the interaction between the neuroendocrine and immune system.

Effects of interleukins on plasma arginine vasopressin and oxytocin levels in conscious, freely moving rats

To elucidate whether interleukins are involved in vasopressin or oxytocin release during cytokine-related stressful conditions, we examined the effects of human interleukin-1 beta and interleukin-6 on plasma vasopressin and oxytocin levels in rats. Interleukin-1 beta administrated intravenously stimulated both the vasopressin and oxytocin secretion in dose-dependent manners. Neither hormone release was observed following interleukin-6 administration. Pretreatment with aspirin significantly attenuated the effects of interleukin-1 beta on both the vasopressin and oxytocin levels. SC-19220, a prostaglandin E2 receptor antagonist, did not affect the interleukin-1 beta-induced increase of plasma oxytocin levels, but almost completely abolished its effect on plasma vasopressin levels. These results suggest that under certain stressful conditions which accompany the stimulation of cytokine production, interleukin-1 is involved in the increase of plasma vasopressin and oxytocin levels and, moreover, different kinds of prostaglandins are suggested to participate in these interleukin-1-induced hormone release.

Tumor necrosis factor receptors in the pituitary cells

To clarify the site and mode of action of tumor necrosis factor (TNF) in the pituitary, we studied the effects, binding sites of TNF and its receptor mRNA in the two types of mouse pituitary-derived cell lines, AtT-20, ACTH-producing cells and TtT/GF, folliculo-stellate (FS)-like cells. First, we examined the expression of TNF receptor mRNA in these cells. Using Northern blot analyses with radiolabeled cDNA to murine TNF receptor p60 and p80 mRNAs as probes, we identified both types of mRNA in the poly(A)-containing RNA prepared from AtT-20 cells and p60 TNF receptor mRNA from TtT/GF. The identified mRNA were compatible in size with those detected in the immune-competent cells. Next, we studied the TNF-binding sites on these cells. Scatchard plot analysis of the significant binding of [125I]TNF revealed a single type of binding site with a Kd (dissociation constant) of 210 pM and 131 binding sites/cell on AtT-20. Similarly on TtT/GF, [125I]TNF showed 353 binding sites/cell with a Kd of 900 pM. [125I]TNF binding on both types of cells competed with TNF and lymphotoxin (TNF beta) in an equimolar fashion. Third, TNF stimulates ACTH synthesis in AtT-20 cells, while TNF increases immunoreactive interleukin (IL)-6 release from TtT/GF cells. These findings demonstrate that AtT-20 and TtT/GF cells are equipped with fully functional TNF receptor system, and suggest that ligand of the receptor, TNF alpha and/or TNF beta, can modulate ACTH synthesis and release as a direct hormonal effector on corticotrophs or indirect modulator through another paracrine mediator, such as IL-6 from FS cells.

The Role of the Phrenic Nerves in Stress Response in Upper Abdominal Surgery

Previous studies have failed to demonstrate a block of the endocrine response to upper abdominal surgery by thoracic epidural analgesia.To clarify the bases for this failure, we compared the effects of epidural analgesia of different dermatome levels up to C8-T2 or C3-4. The patients who received general anesthesia alone showed significant increases of adrenocorticotropic hormone (ACTH) and arginine vasopressin (AVP) immediately after skin incision. The patients with C8-T2 blocked developed significant increases in these hormones, not after the skin incision, but after the intraabdominal procedure. Of the eight patients with C3-4 block, six developed no such responses throughout the study period. The responses of oxytocin (OXT) and prolactin (PRL) were more susceptible to epidural analgesia and were blocked at the C8-T2 level. Growth hormone (GH) showed no correlation with surgical procedures and epidural block. These findings indicate that the nociceptive neural information during upper abdominal surgery is conveyed by the sensory fibers included in both the thoracic and lumbar spinal nerves that innervate the abdominal wall and the intraabdominal viscera, and by the phrenic nerves that innervate the diaphragm. The rationale for postulating the involvement of the phrenic nerves can be referred to the embryonal descent of the diaphragm from the C3-5 myotomes that serves as the upper wall of the abdominal cavity. (Anesth Analg 1996;82:1215-24)

Adrenocorticotropic hormone-releasing activities of interleukins in a homologous invivo system

We compared adrenocorticotropin-releasing activities of several interleukins in a homologous or heterologous in vivo system. Intravenous injection of rat interleukin-1 alpha significantly increased plasma adrenocorticotropin in conscious, freely-moving rats 30 min after the injection, and the effect was 10 times greater than that of human interleukin-1 alpha. Rat interleukin-2 affected plasma adrenocorticotropin in a much slower manner and increased its levels significantly 120 min after the injection. Human interleukin-2 had no effect on plasma adrenocorticotropin. Thus, species difference in the experimental system should be considered to assess the physiological significance of cytokines in the neuroendocrine system.

Chronic effects of interleukin-1 on hypothalamus, pituitary and adrenal glands in rat.

To assess the chronic effects of interleukin-1 (IL-1) and IL-2 on the hypothalamo-pituitary-adrenal axis in vivo, we administered recombinant human (rh) IL-1 alpha, rhIL-1 beta or rhIL-2 (2.0 micrograms/day) repetitively to adult male rats for 10 days. In rhIL-1 beta-treated rats, adrenocorticotropic hormone-like immunoreactivity (ACTH-LI) of the anterior pituitary appeared to increase first on day 3 followed by an increase of corticotropin-releasing hormone (CRH)-LI both in the hypothalamus and in the adrenal gland after day 7. At the end of the 10-day treatment, wet weights of the adrenal glands of rhIL-1 beta-treated rats increased significantly compared with those of control rats. Plasma ACTH levels in rhIL-1 beta-treated rats at the sampling time continued to be elevated throughout the experimental period. Under the same experimental design, rhIL-1 alpha increased plasma ACTH levels at the sampling time without changes in adrenal weight or in the peptide contents investigated. The same amount of rhIL-2 had no effect on these measured variables during the 10-day treatment. These data indicate that the repetitive administration of IL-1 beta resulted in chronic effects in the hypothalamo pituitary-adrenal axis to increase the activities in these organs during the treatment and, moreover, IL-1 possibly has a positive direct effect on the CRH-containing cells in the adrenal glands.

Existence of γ-melanotropin (γ-MSH)-like immunoreactivity in bovine and human pituitary glands

Summary A radioimmunoassay for γ -melanotropin ( γ -MSH) was designed with an antiserum obtained in a rabbit immunized with synthetic γ 3 -MSH. The antiserum cross-reacts with synthetic γ 1 -MSH and γ 2 -MSH and slightly with β -lipotropin, but not with α -MSH, β -MSH, ACTH, and β -endorphin. Using this radioimmunoassay, γ -MSH-like immunoreactivity ( γ -MLI) was detected in bovine and human pituitary glands. Gel chromatographic studies on Bio-Gel P-60 revealed a single component of γ -MLI in the bovine and human anterior pituitary, whereas an additional peak of small γ -MLI was observed in the bovine intermediate lobe.

Effects of food deprivation and high fat diet on opioid receptor binding in rat brain.

The effect of food deprivation for 72 h or a high fat diet on [3H]naloxone binding in the discrete brain regions of male lean Zucker rats was studied. In the midbrain, both treatments increased Bmax for the high-affinity site with no change in Kd. In the cortex, the high fat diet increased Bmax for the high-affinity site. These results suggest that dietary manipulations could produce significant changes in the endogenous opioid system.

Monoamine metabolism and its responses to food deprivation in the brain of Zucker rats

Monoamines and their metabolites levels were simultaneously measured by high-performance liquid chromatography in brain regions of lean and fatty Zucker rats when fed ad lib and deprived of food for 72 hr to evaluate each monoamine metabolism. Metabolite/monoamine ratios were shown for brevity to represent its metabolism. 3-Methoxy-4-hydroxyphenylethyleneglycol/noradrenaline ratios were not affected by the phenotype factor but increased in the cortex of fatty rats and reduced in the midbrain of both phenotypes after fasting; the interaction between phenotype and feeding factors was observed in the cortex and hippocampus. 3,4-Dihydroxyphenylacetic acid/dopamine ratios were increased in the cortex of deprived fatty rats and in the medulla-pons of ad lib-fed fatties compared with lean counterparts and also increased in the striatum of lean rats after food deprivation; the interaction was observed in the cortex, midbrain and medulla-pons. Homovanillic acid/dopamine ratios were decreased in the striatum of deprived fatty rats and in the midbrain and medulla-pons of fatty rats whether deprived or not, but the ratios were not significantly changed by fasting; the interaction was observed in the striatum. 5-Hydroxyindoleacetic acid/5-hydroxytryptamine ratios were reduced in the cortex, striatum and medulla-pons of fatty rats in both feeding states and in the midbrain of deprived fatties, and after food deprivation increased in the cortex and midbrain of lean rats and in the hippocampus of both phenotypes; the interaction was observed in the midbrain.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin E2 (PGE2) induces the c-fos and c-jun expressions via the EP1 subtype of PGE receptor in mouse osteoblastic MC3T3-E1 cells

Abstract. This study examined which subtype(s) of PGE receptors is involved in the induction of c-fos and c-jun by PGE2 in MC3T3-E1 cells. We also investigated the possibility that the induction of these genes is involved in the growth and differentiation of this cell line. PGE2 dose-dependently induced c-fos and c-jun mRNA expressions in MC3T3-E1 cells. Of the PGE analogs, 17-phenyl-ω-trinor PGE2 (EP1 agonist) and sulprostone (EP1/EP3 agonist) were far more potent than butaprost (EP2 agonist) and 11-deoxy PGE1 (EP2/EP4 agonist) in inducing c-fos and c-jun mRNA expressions. Since MC3T3-E1 cells do not express the EP3 subtype, these results suggest that PGE2 induces c-fos and c-jun mRNA expressions through the EP1 subtype of its receptor. In order to study the functional relevance of these protooncogenes, we then studied the effect of inhibition of their synthesis by the use of antisense oligonucleotide. Alkaline phosphatase (ALP) suppression by 17-phenyl-ω-trinor PGE2 was reversed by antisense oligonucleotide for either c-fos or c-jun. These results suggest that PGE2, via the EP1 subtype of the PGE receptor, negatively modulates the transition from proliferation to the matrix maturation stage through the induction of c-fos and c-jun. However, antisense oligonucleotide for c-fos or c-jun did not alter the prostaglandin G/H synthase-2 mRNA expression induced by EP1. Thus, it is possible that c-fos and c-jun inductions do not account for all the EP1-mediated PGE2 actions in MC3T3-E1 cells.