Naotoshi Murakami

ACTH response induced by interleukin-1 is mediated by CRF secretion stimulated by hypothalamic PGE.

We investigated whether hypothalamic prostaglandin E2 (PGE2) and corticotropin releasing factor (CRF) are responsible for the development of the adrenocorticotropic hormone (ACTH) response induced by interleukin-1α (IL-1α). The present results show that ACTH responses induced by intravenous injection of IL-1α were suppressed by systemic pretreatment with indomethacin and that intrahypothalamic injection of PGE2 stimulates the secretion of ACTH. Furthermore, systemic pretreatment with anti-CRF antibody significantly suppressed the ACTH response induced by intrahypothalamic injection of PGE2. These data suggest that the ACTH response induced by IL-1 is mediated by CRF secretion stimulated by hypothalamic PGE2.

Possible involvement of prostaglandin E in development of ACTH response in rats induced by human recombinant interleukin-1.

1. Intravenous (I.V.) injection of human recombinant interleukin‐1 alpha (IL‐1 alpha) produced dose‐dependent monophasic fevers in rats. Moreover, the I.V. injection of IL‐1 alpha produced dose‐dependent rises in the plasma concentrations of adrenocorticotrophic hormone (ACTH) 30 min after injections with dosages of 5 micrograms/kg and 15 micrograms/kg of IL‐1 alpha. 2. The febrile responses induced by the I.V. injection of IL‐1 alpha (15 micrograms/kg) were completely abolished, and conversely hypothermia occurred, when the animals were pre‐treated with a cyclo‐oxygenase inhibitor, indomethacin (INDO). Pre‐treatment with INDO also inhibited the increase in the plasma concentrations of ACTH induced by I.V. injection of IL‐1 alpha (15 micrograms/kg), indicating that enhancement of plasma concentrations of ACTH induced by I.V. injection of IL‐1 alpha is processed through the action of prostaglandins. 3. Intrapreoptic injection of prostaglandin E2 produced a dose‐dependent fever with a rapid onset at doses of 25 and 100 ng. Moreover, the intrapreoptic injection of prostaglandin E2 increased the plasma concentrations of ACTH in a dose‐dependent manner 30 min after injections. 4. The intrapreoptic injection of IL‐1 alpha (20 ng) caused slow monophasic fever. However, no significant elevation of plasma concentrations of ACTH was observed 30, 90 and 180 min after the intrapreoptic injection of IL‐1 alpha, as compared with the ACTH levels at each time in the control group which received an intrapreoptic injection of saline. 5. These results suggest that intrapreoptic prostaglandin E plays an important role in the ACTH response by inducing the release of corticotrophin‐releasing factor (CRF).

Multiple control of fever production in the central nervous system of rabbits.

1. The effects of microinjection of prostaglandin D2, E2 and F2 alpha and of endogenous pyrogen on the rectal temperature of rabbits were extensively examined in sixty‐eight brain regions and in the third cerebral ventricle. 2. Intracerebroventricular injection of both prostaglandins E2 and F2 alpha produced dose‐dependent fever over a range of 100‐1000 ng. The selective brain regions, the nucleus broca ventralis, preoptic area, anterior hypothalamus and the ventromedial hypothalamus, responded to microinjections of a small dose (less than 200 ng) of prostaglandins E2 and F2 alpha by producing fever. Furthermore, the lateral hypothalamus, ventral thalamus, substantia nigra and the trigeminal nucleus were also sensitive to high concentrations of prostaglandins E2 and F2 alpha, fever being produced. It is likely that prostaglandin D2 is not involved in fever induction. 3. The ventricular injection of endogenous pyrogen also produced fever. However, brain regions sensitive to microinjection of endogenous pyrogen were exclusively localized to regions near the organum vasculosum laminae terminalis (OVLT), such as the nucleus broca ventralis and the preoptic area. In contrast to the monophasic fever induced by prostaglandins E2 and F2 alpha, about 30 min after ventricular or cerebral injection of endogenous pyrogen the rectal temperature gradually started to rise and the fever was prolonged over 4 h. 4. We investigated the effect of an inhibitor of prostaglandin synthesis, sodium salicylate, on biphasic fever induced by intravenous injection of bacterial endotoxin. The microinjections of sodium salicylate into the bilateral regions near the OVLT suppressed the second peak but had no effect on the first peak. 5. The present study clarifies that there exist two separate mechanisms of induction of biphasic fever. Correlating with the first peak of biphasic fever, prostaglandins synthesized outside the blood‐brain barrier act on multiple sites in the central nervous system to induce fever. Correlating with the second peak, endogenous pyrogen acts on regions near the OVLT to synthesize and release pyrogenic prostaglandins.

Evidence for separate mechanisms of induction of biphasic fever inside and outside the blood‐brain barrier in rabbits.

1. Intravenous bacterial endotoxin, or endogenous pyrogen, in high concentration both caused biphasic fever in rabbits. In low concentration they produced only the first phase of fever. 2. Subcutaneous indomethacin suppressed the first phase of fever produced by high concentration of intravenous endotoxin or endogenous pyrogen, but not the second phase. 3. Intraventricular cerebral injection of indomethacin reduced the second phase of fever produced by high concentration of intravenous endotoxin or endogenous pyrogen, but not the first phase. 4. Intraventricular cerebral injection of endotoxin or of endogenous pyrogen caused slow monophasic fever. This was suppressed by intraventricular, but not by subcutaneous, indomethacin. 5. It is concluded that the first phase of biphasic fever is caused by pyrogen acting via structures outside the blood‐brain barrier, presumably peripheral nerves, and the second phase by pyrogen acting via structures within the blood‐brain barrier, presumably hypothalamic neurones.

Interleukin‐1 beta production in the rabbit brain during endotoxin‐induced fever.

Interleukin‐1 beta (IL‐1 beta) production in the brain and the spleen was investigated in rabbits made febrile by intravenous (I.V.) injection of endotoxin, or human recombinant IL‐1 beta (hIL‐1 beta). The endotoxin used in the present study was the lipopolysaccharide (LPS) of Salmonella typhosa endotoxin. Monophasic fever was induced by I.V. injection of a low dose of LPS (0.02 micrograms kg‐1) and biphasic fever by I.V. injection of a large dose of LPS (4 micrograms kg‐1), a sublethal dose of LPS (40 micrograms kg‐1) or hIL‐1 beta (2 micrograms kg‐1). In situ hybridization and immunohistochemical studies revealed that, although no IL‐1 beta production was observed in the brain at 1 and 3 h after injection of a low dose of LPS (0.02 micrograms kg‐1) or of hIL‐1 beta (2 micrograms kg‐1), IL‐1 beta production was demonstrated in organum vasculosum laminae terminalis (OVLT) and some cells around the blood vessels in the parenchyma 1 h after 4 micrograms kg‐1 LPS. IL‐1 beta production was detected throughout the brain after 40 micrograms kg‐1 LPS. Pretreatment with indomethacin, an inhibitor of prostaglandin synthesis, did not affect IL‐1 beta production in the brain induced by 4 micrograms kg‐1 LPS. The cell type which produces IL‐1 beta in the OVLT following LPS injection was confirmed to be a macrophage by electron microscopy. The cells producing IL‐1 beta in the parenchyma were determined to be microglial cells. In the spleen, each dose of LPS induced a significant increase in IL‐1 beta production in polymorphonuclear cells and macrophages in the red pulp 1 h after injection. However, 2 micrograms kg‐1 hIL‐1 beta did not induce IL‐1 beta production in the spleen. The present results show clearly that systemic administration of LPS induces IL‐1 beta production in the OVLT which may be responsible for induction of the second phase of biphasic fever. The production of IL‐1 beta in the OVLT was not attributable to the action of peripherally synthesized IL‐1 beta or prostaglandins.

Central action sites of interleukin-1 beta for inducing fever in rabbits.

1. Intravenous (I.V.) human recombinant interleukin‐1 beta (IL‐1 beta) in high doses caused biphasic fever in rabbits. In lower doses it produced only the first phase of fever. 2. Intracerebroventricular (I.C.V.) or intrapreoptic‐anterior hypothalamic (IPOAH) injection of IL‐1 beta produced a rather rapid and marked increase in rectal temperature. 3. Subcutaneously administered indomethacin partly reduced the first phase and more substantially the second phase of the biphasic fever induced by high doses of I.V. IL‐1 beta. The first phase may thus be prostaglandin independent at least in part. 4. In the fever induced by I.C.V. injection of IL‐1 beta, subcutaneous indomethacin reduced the elevation of the rectal temperature considerably and delayed the onset of fever. Administration of indomethacin (I.C.V.) caused marked inhibition of the fever induced by a lower I.C.V. dose of IL‐1 beta, but with a high dose the onset of the fever was delayed for about 1 h, without the total rise being affected. 5. It is concluded that the first phase of biphasic fever is caused by IL‐1 beta acting via an extravascular component of the organum vasculosum laminae terminalis (OVLT) or the circumventricular organs accessible from only the blood side, to release arachidonate metabolites, presumably prostaglandin E2 (PGE2), and the second phase by IL‐1 beta acting via the blood‐brain interface accessible both from the blood side and the brain side, to release metabolites other than PGE2.

Sympatho-adrenal involvement in methamphetamine-induced hyperthermia through skeletal muscle hypermetabolism.

We investigated the involvement of the sympatho-adrenal axis in the hyperthermia induced by methamphetamine by using a biotelemetric system. The intraperitoneal injection of methamphetamine (1 mg/kg) induced hyperthermia preceded by an increase in oxygen consumption in freely moving rats. The hyperthermic effect of methamphetamine was completely blocked by chemical sympathectomy with 6-hydroxydopamine (50 mg/kg, i.p.). Adrenalectomy, but not adrenal demedullation, prevented the hyperthermia. In adrenalectomized rats, dexamethasone supplementation (0.5 mg/kg, s.c.) restored the methamphetamine-induced hyperthermia. Furthermore, dantrolene (1 or 2 mg/kg, i.v.), which blocks Ca2+ release from the sarcoplasmic reticulum in skeletal muscle, attenuated the hyperthermia. These results suggest that methamphetamine stimulates norepinephrine release from sympathetic nerve terminals, which then enhances thermogenesis in skeletal muscle under the permissive action of glucocorticoids.

Activation of ACTH release is mediated by the same molecule as the final mediator, PGE2, of febrile response in rats ☆

Increase in the blood level of adrenocorticotropic hormone (ACTH) and fever are induced by i.v. administration of interleukin-1 alpha (IL-1 alpha) in rats. With preinjection of indomethacin, the ACTH and fever responses to i.v. IL-1 alpha were both either greatly reduced or abolished. Intrapreoptic microinjection of prostaglandin E2 (PGE2) caused ACTH and fever responses similar to those seen after i.v. IL-1 alpha. These data suggest that PGE2, a final mediator of fever, may be released by i.v. IL-1 alpha and also act centrally to enhance the release of corticotropic-releasing factor in the brain.

Fever and acute phase response induced in rabbits by human recombinant interferon‐gamma.

1. Intravenous (I.V.) and intracerebroventricular (I.C.V.) injections of human recombinant interferon‐gamma (IFN‐gamma) produced dose‐dependent fevers in rabbits. The fever induced by I.V. injection was monophasic and the maximum elevation occurred 80‐110 min after injection. The fever induced by I.C.V. injection was observed from about 20 min after injection and was remarkably prolonged over 4 h. 2. The development of pyrogenic tolerance to IFN‐gamma was observed when rabbits were given I.V. injections on 3 successive days. Furthermore, the pyrogenicity of IFN‐gamma was significantly attenuated by heating at 60 degrees C for 40 min. The I.V. injection of IFN‐gamma enhanced the febrile response induced by endotoxin but had no effect on that induced by endogenous pyrogen. 3. The I.V. injection of a large dose of IFN‐gamma (6 x 10(6) units/kg) induced an acute phase response, which included a reduction in plasma concentration of iron and zinc. 4. The present results suggest that IFN‐gamma released from lymphocytes is one of the endogenous mediator proteins responsible for producing fever and acute phase response.

Effects of endurance training on myosin heavy-chain isoforms and enzyme activity in the rat diaphragm

We investigated the effects of endurance training (20 m/min, 60 min/day, 5 days/week) on myosin heavy-chain (MHC) isoforms and succinic dehydrogenase (SDH) activity in rat crural and costal diaphragms, and plantaris muscles. Although the 4-week endurance training produced significant (P<0.05) increases, both in SDH activity and the percentage of isoform HCIIa in the plantaris of the trained rat compared with the sedentary control rat, these alterations did not occur in either the crural or costal diaphragms. After 10 weeks of endurance training, trained animals had significantly (P<0.05) higher SDH activity in the costal diaphragm and the plantaris. Moreover, a significant (P<0.05) decrease occurred in the percentage of HCIIb in the costal diaphragm, and a significant (P<0.01) decrease in the percentage of HCIIb concomitant with a significant (P<0.05) increase of HCIIa resulted in the plantaris. However, the crural diaphragm did not show any significant changes after 10 weeks of endurance training. These results indicate that endurance training induces an alteration in the expression of an MHC phenotype, in addition to causing an increase in oxidative enzyme activity. However, the alterations in response to endurance training are apparently not uniform, varying between regions and/or kinds of muscles.