Peripheral administration of alpha-MSH reduces fever in older and younger rabbits

Melanocortin Regulation of Inflammation

Adrenocorticotropic hormone (ACTH), and α-, β-, and γ-melanocyte-stimulating hormones (α-, β-, γ-MSH), collectively known as melanocortins, together with their receptors (melanocortin receptors), are components of an ancient modulatory system. The clinical use of ACTH in the treatment of rheumatoid arthritis started in 1949, originally thought that the anti-inflammatory action was through hypothalamus-pituitary-adrenal axis and glucocorticoid-dependent. Subsequent decades have witnessed extensive attempts in unraveling the physiology and pharmacology of the melanocortin system. It is now known that ACTH, together with α-, β-, and γ-MSHs, also possess glucocorticoid-independent anti-inflammatory and immunomodulatory effects by activating the melanocortin receptors expressed in the brain or peripheral immune cells. This review will briefly introduce the melanocortin system and highlight the action of melanocortins in the regulation of immune functions from in vitro, in vivo, preclinical, and clinical studies. The potential therapeutic use of melanocortins are also summarized.

Tuberculosis in ageing: high rates, complex diagnosis and poor clinical outcomes

BACKGROUND

worldwide, the frequency of tuberculosis among older people almost triples that observed among young adults.

OBJECTIVE

to describe clinical and epidemiological consequences of pulmonary tuberculosis among older people.

METHODS

we screened persons with a cough lasting more than 2 weeks in Southern Mexico from March 1995 to February 2007. We collected clinical and mycobacteriological information (isolation, identification, drug-susceptibility testing and IS6110-based genotyping and spoligotyping) from individuals with bacteriologically confirmed pulmonary tuberculosis. Patients were treated in accordance with official norms and followed to ascertain treatment outcomes, retreatment, and vital status.

RESULTS

eight hundred ninety-three tuberculosis patients were older than 15 years of age; of these, 147 (16.5%) were 65 years of age or older. Individuals ≥ 65 years had significantly higher rates of recently transmitted and reactivated tuberculosis. Older age was associated with treatment failure (OR=5.37; 95% CI: 1.06-27.23; P=0.042), and death due to tuberculosis (HR=3.52; 95% CI: 1.78-6.96; P<0.001) adjusting for sociodemographic and clinical variables.

CONCLUSIONS

community-dwelling older individuals participate in chains of transmission indicating that tuberculosis is not solely due to the reactivation of latent disease. Untimely and difficult diagnosis and a higher risk of poor outcomes even after treatment completion emphasise the need for specific strategies for this vulnerable group.

Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases

Alpha-MSH is a tridecapeptide derived from proopiomelanocortin. Many studies over the last few years have provided evidence that alpha-MSH has potent protective and antiinflammatory effects. These effects can be elicited via centrally expressed melanocortin receptors that orchestrate descending neurogenic antiinflammatory pathways. alpha-MSH can also exert antiinflammatory and protective effects on cells of the immune system and on peripheral nonimmune cell types expressing melanocortin receptors. At the molecular level, alpha-MSH affects various pathways implicated in regulation of inflammation and protection, i.e., nuclear factor-kappaB activation, expression of adhesion molecules and chemokine receptors, production of proinflammatory cytokines and mediators, IL-10 synthesis, T cell proliferation and activity, inflammatory cell migration, expression of antioxidative enzymes, and apoptosis. The antiinflammatory effects of alpha-MSH have been validated in animal models of experimentally induced fever; irritant and allergic contact dermatitis, vasculitis, and fibrosis; ocular, gastrointestinal, brain, and allergic airway inflammation; and arthritis, but also in models of organ injury. One obstacle limiting the use of alpha-MSH in inflammatory disorders is its pigmentary effect. Due to its preserved antiinflammatory effect but lack of pigmentary action, the C-terminal tripeptide of alpha-MSH, KPV, has been delineated as an alternative for antiinflammatory therapy. KdPT, a derivative of KPV corresponding to amino acids 193-195 of IL-1beta, is also emerging as a tripeptide with antiinflammatory effects. The physiochemical properties and expected low costs of production render both agents suitable for the future treatment of immune-mediated inflammatory skin and bowel disease, fibrosis, allergic and inflammatory lung disease, ocular inflammation, and arthritis.

Effects of alpha-MSH on kainic acid induced changes in core temperature in rats

The effects of intraperitoneal (i.p.) administration of kainic acid (KA) and alpha-melanocyte-stimulating hormone (alpha-MSH) alone or in combination, on core temperature of freely moving rats were examined. KA or saline was administered once (10 mg/kg) and alpha-MSH or saline was given repeatedly i.e. 10 min before and 10, 30 and 60 min after the administration of saline or KA. Two doses of alpha-MSH were used: 0.5 and 2.5 mg/kg. KA alone produced a biphasic effect on core temperature, i.e. an initial short-lasting hypothermia followed by hyperthermia that lasted about 6 h. The higher dose of alpha-MSH had a potentiating effect on KA-induced hypothermia, while the lower dose of alpha-MSH increased the hyperthermia produced by KA. alpha-MSH administered alone produced a late (3 h), dose-dependent increase in core temperature. It is conceivable that repeated administration of alpha-MSH in the doses used in our study may cause a cumulative effect in raising body temperature for a limited period of time. The previously described interactions between KA and alpha-MSH, respectively, with dopaminergic and serotoninergic systems may account for the effects on core temperature in rats observed in our study.

Does aging modify pulmonary tuberculosis?: A meta-analytical review

STUDY OBJECTIVES

To evaluate the differences in the clinical, radiologic, and laboratory features of pulmonary tuberculosis (TB) in older patients, as compared to younger patients.

DESIGN

A meta-analysis (the Schmidt-Hunter method) of published works found in MEDLINE and other sources was performed. A total of 12 studies were collected, and each variable was submitted to meta-analysis.

RESULTS

No differences were found between older (>/= 60 years old) and younger TB patients with respect to male predominance, evolution time before diagnosis, prevalence of cough, sputum production, weight loss, fatigue/malaise, radiographic upper lobes lesions, positive acid-fast bacilli in sputum, anemia or hemoglobin level, and serum aminotransferases. A lower prevalence of fever, sweating, hemoptysis, cavitary disease, and positive purified protein derivative, as well as lower levels of serum albumin and blood leukocytes were noticed among older patients. In addition, the older population had a greater prevalence of dyspnea and some concomitant conditions, such as cardiovascular disorders, COPD, diabetes, gastrectomy history, and malignancies.

CONCLUSIONS

This meta-analytical review identified the main differences of older TB patients, as compared to younger TB patients, that should be considered during the diagnostic evaluation. Most of these differences are explained by the already known physiologic changes that occur during aging.

The long term acute phase-like responses that follow acute stressor exposure are blocked by alpha-melanocyte stimulating hormone

Both intracerebroventricular (i.c.v.) IL-1beta and exposure to inescapable tail shock (IS) activate acute phase responses (APRs) that include increases in core body temperature (CBT), increases in hypothalamic-pituitary-adrenal activity, decreases in carrier proteins such as corticosterone binding globulin (CBG), aphagia and adipsia. A variety of data suggested that stressors produce APRs by inducing brain IL-1beta. The current series of studies further explored this possibility by determining whether the functional IL-1beta antagonist, alpha-melanocyte-stimulating hormone (alpha-MSH(1-13)), would block IS-induced APRs. Immediately following i.c.v. alpha-MSH(1-13) administration, rats were exposed to a single session of 100, 5 s, 1.6 mA ISs, or control treatment (home cage control). alpha-MSH(1-13) blocked IS-induced increased CBT, increased plasma corticosterone (CORT), decreased CBG, aphagia and adipsia 24 h after IS. The inhibitory effects of alpha-MSH(1-13) were shown not to be a consequence of alpha-MSH(1-13) producing its actions 24 h after its administration because alpha-MSH(1-13) given 24 h before IS did not block IS-induced increased CBT and CORT during IS. Additionally, alpha-MSH(1-13), given 24 h before IS, had no effect on increased CBT, increased CORT, decreased CBG, adipsia, or aphagia 24 h after IS. These data provide support for a specific mode of action for i.c.v. alpha-MSH(1-13), namely blockade of APRs with no impact on acute hyperthermia or increased levels of CORT produced during IS.

Melanocortin peptides inhibit production of proinflammatory cytokines in blood of HIV-infected patients

Melanocortins are proopiomelanocortin-derived peptides that include adrenocorticotropic hormone [ACTH (1-39)], alpha-melanocyte-stimulating hormone [alpha-MSH (1-13)], and related amino acid sequences. Melanocortin peptides have potent antiinflammatory/anticytokine activity. Because cytokines such as interleukin 1 (IL-1) and tumor necrosis factor (TNF) can be detrimental in HIV-infected patients, we investigated the effects of melanocortins on production of IL-1 and TNF alpha in the blood of HIV patients. Cytokine production was measured in whole blood samples stimulated with LPS in the presence or absence of alpha-MSH (1-13), alpha-MSH (11-13), ACTH (1-24), or ACTH (1-39). Melanocortins reduced production of both cytokines in a concentration-dependent fashion. In separate experiments on normal peripheral blood mononuclear cells (PBMC), alpha-MSH (1-13) inhibited production of IL-1 beta and TNF alpha induced by HIV envelope glycoprotein gp 120. These results suggest that stimulation of melanocortin receptors in inflammatory cells could be a novel way to reduce production of cytokines that promote HIV replication.

The administration of an alpha-MSH analogue reduces the serum release of IL-1 alpha and TNF alpha induced by the injection of a sublethal dose of lipopolysaccharides in the BALB/c mouse

The injection of alpha-MSH or of one of its analogues ([Nle4-D.Phe7] alpha-MSH4-10) reduced, in vivo, the release of two cytokines (IL-1 alpha and TNF alpha) involved in inflammation. The inflammatory state was induced in BALB/c mice by intraperitoneal injection of a sublethal dose of lipopolysaccharides (LPS). The assay of these cytokines by ELISA showed a reduction of 20% with alpha-MSH and between 30 and 60% with the alpha-MSH analogue. The alpha-MSH or the analogue was administered in one of two ways: intravenously or subcutaneously. The most efficient method seemed to be the subcutaneous one because it improved the activity 10,000 times more than the intravenous method. Moreover, the analogue induced a regression of mortality in the animals treated by the intravenous method. Our results show that alpha-MSH and one of its analogues inhibit IL-1 alpha and TNF alpha, and can be used as anti-inflammatory molecules.

Fever: causes and consequences

The present review distinguishes pathogenic, neurogenic, and psychogenic fever, but focuses largely on pathogenic fever, the hallmark of infectious disease. The data presented show that a complex cascade of events underlies pathogenic fever, which in broad outline - and with frank disregard of contradictory data - can be described as follows. An invading microorganism releases endotoxin that stimulates macrophages to synthesize a variety of pyrogenic compounds called cytokines. Carried in blood, these cytokines reach the perivascular spaces of the organum vasculosum laminae terminalis (OVLT) and other regions near the brain where they promote the synthesis and release of prostaglandin (PGE2). This prostaglandin then penetrates the blood-brain barrier to evoke the autonomic and behavioral responses characteristic of fever. But then once expressed, fever does not continue unchecked; endogenous antipyretics likely act on the septum to limit the rise in body temperature. The present review also examines fever-resistance in neonates, the blunting of fever in the aged, and the behaviorally induced rise in body temperature following infection in ectotherms. And finally it takes up the question of whether fever enhances immune responsiveness, and through such enhancement contributes to host survival.

Alpha-melanocyte-stimulating hormone suppresses fever and increases in plasma levels of prostaglandin E2 in the rabbit

1. The effect of alpha-melanocyte-stimulating hormone (alpha-MSH) on changes in body temperature and plasma levels of prostaglandin E2 (PGE2) were measured in the rabbit following intravenous injection of bacterial lipopolysaccharide (LPS), rabbit endogenous pyrogen (EP), human recombinant tumour necrosis factor-alpha (TNF-alpha), human recombinant interleukin-1 beta (IL-1 beta) and intracerebroventricular injection of PGE2. 2. LPS (25 ng kg-1), EP (25 microliters kg-1), TNF-alpha (11 micrograms kg-1) and IL-1 beta (5 ng kg-1) produced increases in body temperature simultaneously with increases in plasma PGE2 levels. alpha-MSH (5 or 10 micrograms kg-1) attenuated both the increase in body temperature and increases in plasma levels of PGE2. 3. Intracerebroventricular injection of PGE2 (500 ng) produced a monophasic increase in body temperature. alpha-MSH (5 micrograms kg-1) administered 20 min after PGE2 had no effect on the hyperthermic response. 4. alpha-MSH (10 micrograms kg-1) had no effect on either body temperature or plasma levels of PGE2 in response to I.V. injection of sterile saline. 5. These data demonstrate that alpha-MSH inhibits both the pyrogenic actions of LPS, EP, TNF-alpha and IL-1 beta and their ability to increase PGE2 release without affecting the direct actions of PGE2, suggesting the possibility that alpha-MSH may prevent the synthesis of PGE2 either by preventing the actions or release of mediators such as TNF-alpha and IL-1 in response to LPS.

The effect of alpha-MSH on fever caused by Staphylococcus aureus cell walls in rabbits

The role of endogenous pyrogens induced by gram-positive bacterial pyrogens is not known. Intravenous alpha-MSH (2.5 micrograms) significantly reduced only the first phase of the biphasic thermal response to IV S. aureus cell walls (5 x 10(7)). Intracerebroventricular alpha-MSH (200 ng) had no effect on the fever response. The fall in serum iron concentration was significantly attenuated by the IV alpha-MSH but was not affected by the ICV alpha-MSH. Intravenous alpha-MSH had no effect on fever or the serum iron response caused by muramyl dipeptide (MDP). We conclude that the first phase of the thermal response to S. aureus cell walls is mediated by an endogenous pyrogen (EP) and the second phase of the response by a mechanism not involving EP, but possibly a muramyl peptide.

Effects of alpha-melanocyte stimulating hormone on fever caused by endotoxin in rabbits

1. We measured the effect of intravenous and intracerebroventricular injections of alpha-melanocyte stimulating hormone (alpha-MSH) on changes in body temperature and serum iron concentration following i.v. injection of endotoxin in rabbits. 2. Intravenous alpha-MSH (2.5 micrograms) significantly reduced both phases of endotoxin fever and attenuated the fall in serum iron concentration which follows endotoxin injection. 3. Intracerebroventricular alpha-MSH (200 ng) reduced only the second phase of the fever and had no effect on the fall in the serum iron concentrations. 4. We conclude that alpha-MSH, in doses that are known to inhibit endogenous pyrogen fever, inhibits the fever induced by endotoxin in rabbits, probably by blocking the actions of endogenous pyrogens mediating the endotoxin fever.

Anti-inflammatory activity of alpha-MSH(11-13) analogs: influences of alteration in stereochemistry

D-Amino acid substitutions in the anti-inflammatory/antipyretic Ac-alpha-MSH(11-13)-NH2 tripeptide of Ac-alpha-MSH(1-13)-NH2 were made and the altered peptides were injected in mice treated with picryl chloride. Ear swelling, measured 3 and 6 h after application of the irritant, was reduced by IP injections of Ac-alpha-MSH(11-13)-NH2, in confirmation of previous observations. Ac-[D-Lys11]alpha-MSH(11-13)-NH2 effected similar anti-inflammatory activity but Ac-[D-Pro12]alpha-MSH(11-13)-NH2 was inactive. Ac-[D-Val13]alpha-MSH(11-13)-NH2 and Ac-[D-Lys11,D-Val13]alpha-MSH(11-13)-NH2 generally had greater anti-inflammatory activity than the parent tripeptide molecule; the dose-response relations exhibited the bell-shaped characteristics seen previously with MSH peptides. The results indicate that the L-Pro12 is essential for the anti-inflammatory activity of Ac-alpha-MSH(11-13)-NH2 whereas the L-Lys11 is not. D-Val13 substitution increased anti-inflammatory activity approximately four-fold over Ac-alpha-MSH(11-13)-NH2. These results provide new structure-activity relationships of the anti-inflammatory Ac-alpha-MSH(11-13)-NH2 molecule. The data support the developing idea that alpha-MSH and its COOH-terminal fragments modulate host responses, perhaps by antagonizing the actions of cytokines.

Response of body temperature and serum iron concentration to repeated pyrogen injection in rabbits

We measured body temperature and serum iron concentration after five daily consecutive injections of febrile doses of Salmonella typhosa lipopolysaccharide (0.1 micrograms/kg) and two doses of Staphylococcus aureus cell walls (1 x 10(7) and 5 x 10(7) cells) in rabbits. Tolerance to endotoxin injection, as manifest by a significant attenuation in the body temperature elevation, developed after the first injection of endotoxin. The endotoxin-induced fall in serum iron concentration was attenuated significantly by the 5th day of endotoxin injection. In contrast, no tolerance developed in either the body temperature or serum iron response following repeated daily injections of S. aureus. Rabbits rendered tolerant to endotoxin showed normal febrile and serum iron responses to subsequent S. aureus injection. Rabbits given serial injections of S. aureus, although not tolerant to S. aureus itself, exhibited attenuated body temperature responses but not serum iron responses to endotoxin injection. We suggest that repeated injection of endotoxin diminishes the ability of endotoxin to stimulate endogenous pyrogen (EP) synthesis and/or release, a property not shared by the gram-positive pyrogen S. aureus. However, repeated injection of S. aureus weakens the central endotoxin-EP pathway.

Depletion of brain alpha-MSH alters prostaglandin and interleukin fever in rats

Alpha-melanocyte stimulating hormone (alpha-MSH), a putative endogenous antipyretic agent, is synthesized largely within neurons in the arcuate nucleus. To test the hypothesis that destruction of this area would increase the febrile response, male Wistar rats, treated as neonates with intraperitoneal injections of monosodium glutamate (MSG) or saline, were given intracerebroventricular (i.c.v.) injections of prostaglandin E1 (20 ng; 200 ng) or purified interleukin-1 (20 U) and body temperature was monitored. The fevers displayed by the MSG-treated animals were significantly greater (P less than 0.05) than those of the controls for the lower dose of PGE1 at 10-30 min and for IL-1 at 3-6 h after the injections. MSG-treated rats showed significant reduction (P less than 0.01) in alpha-MSH content of the medial basal hypothalamus and lateral septum when compared to saline controls. Body temperature response of non-febrile animals to high ambient temperature was not affected by the MSG treatment. These data support the hypothesis that alpha-MSH is an endogenous antipyretic in the rat.

Alpha-MSH peptides inhibit acute inflammation and contact sensitivity

Alpha-melanocyte stimulating hormone [alpha-MSH(1-13)] occurs within the CNS, skin, circulation and in other body sites. This tridecapeptide and its COOH-terminal tripeptide, alpha-MSH (11-13), have antipyretic and anti-inflammatory actions. Studies of the anti-inflammatory effects of these molecules have been confined mainly to tests of inhibition of histamine and endogenous pyrogen-induced increases in capillary permeability in rabbits and acute inflammation of ear tissue in mice. The aim in the present experiments was to learn if alpha-MSH peptides also antagonize inflammation in two additional models: acute edema induced in the mouse paw and contact sensitivity. Significant anti-inflammatory effects were observed with MSH peptides in both models. These findings converge with previous results to indicate that alpha-MSH peptides modulate inflammation. Because circulating alpha-MSH increases after treatment of animals with endogenous pyrogen or endotoxin, administration of the peptides may simply mimic a naturally occurring modulation of host defense reactions.

Antipyretic effect of central alpha-MSH summates with that of acetaminophen or ibuprofen

The neuropeptide alpha-melanocyte stimulating hormone has potent antipyretic properties when given centrally or systemically. Little is known about the mechanism of the antipyretic action and virtually nothing is known about interactions among the antipyretic effects of alpha-MSH and commonly used antipyretic agents. Randomized studies in which alpha-MSH, acetaminophen or ibuprofen, or a combination of alpha-MSH and antipyretic drug, were given IV to rabbits made febrile by endogenous pyrogen, indicate that the antipyretic effect of the peptide is summative with those of the drugs. alpha-MSH has been shown to have a wide safety margin in earlier research and the results suggest that combinations of peptide and antipyretic drugs might be safer and have fewer side effects than larger quantities of the drugs alone.

Repeated central administration of alpha-MSH does not alter the antipyretic effect of alpha-MSH in young and aged rabbits

alpha-Melanocyte-stimulating hormone is a potent antipyretic when administered centrally or peripherally; however, there are no previous data on development of tolerance to the antipyretic action of this neuropeptide. In previous research, aged rabbits were more sensitive to low doses of alpha-MSH than young rabbits. We tested the antipyretic action of alpha-MSH in young and old rabbits after twice daily injections of the peptide for 10 days. Neither aged nor younger rabbits showed altered responses to alpha-MSH. This lack of tolerance underscores the importance of alpha-MSH to physiological control and survival of the host.

Antipyretic properties of centrally administered alpha-MSH fragments in the rabbit

alpha-Melanocyte stimulating hormone (alpha-MSH 1-13) has marked antipyretic effects when administered centrally or peripherally in small doses. A C-terminal fragment, alpha-MSH (11-13), contains an antipyretic message sequence of alpha-MSH; however, the lesser potency of this fragment relative to that of the entire molecule suggests that other amino acids of the alpha-MSH sequence are essential for the full antipyretic effect. Graded doses of alpha-MSH (11-13) (Ac LysProVal NH2), alpha-MSH (10-13) (Ac GlyLysProVal NH2), and alpha-MSH (8-13) (Ac ArgTrpGlyLysProVal NH2), were injected into the cerebral ventricles of rabbits made febrile by IV administration of crude interleukin-1. All three fragments reduced fever in a dose-related manner. The (8-13) sequence was much more effective than the other two fragments, and the (10-13) portion was less effective than the (11-13) tripeptide. None of the fragments was as potent as alpha-MSH (1-13). The results confirm that an antipyretic message resides within alpha-MSH (11-13) and sequential addition of amino acids to alpha-MSH (11-13) can both enhance and reduce the potency of the fragment.

Stimulation of follicular melanogenesis in the mouse by topical and injected melanotropins

The effects of melanocyte-stimulating hormone (alpha-MSH) and related analogs on follicular melanogenesis in the mouse (C57BL/6JA gamma) were studied. [Nle4, D-Phe7]-alpha-MSH and the related fragment analogues Ac-[Nle4, D-Phe7]-alpha-MSH4-11-NH2 and Ac-[Nle4, D-Phe7]-alpha-MSH4-10-NH2, stimulated the conversion of pheomelanogenesis to eumelanogenesis when subcutaneously injected at concentrations 100-fold lower than the native hormone, alpha-MSH. In addition, the melanotropin analogs stimulated follicular eumelanogenesis when applied topically to the skin of mice. The melanotropins were transdermally delivered to the systemic circulation as evidenced by the fact that eumelanogenesis was stimulated in hair follicles in areas distant from the site of topical application. These results demonstrate that peptide hormone analogs can be transported across the skin. The unique actions of the melanotropin analogs may relate to the fact that these peptides are nonbiodegradable and thus exert prolonged actions on melanocytes. These compounds may prove important for studies on normal integumental melanogenesis and for the treatment of hypopigmentary disorders in humans.

Is the endogenous antipyretic neuropeptide alpha-MSH responsible for reduced fever in aged rabbits?

The reduced febrile response in aged man has been noted since the beginning of clinical thermometry. Our previous research on aged rabbits and squirrel monkeys disclosed a similar reduced fever, presumably due to a decrease in central receptors for endogenous pyrogen. However, because central alpha-melanocyte stimulating hormone (MSH) appears to have a potent role in physiological control of fever, it may be that increased release of the peptide is responsible for the reduced febrile response in aged animals. To test this idea, antiserum specific to MSH was administered intracerebroventricularly to rabbits of known age. The antiserum given according to three schedules of treatment augmented fever caused by IV injections of interleukin-1 (IL-1) in young (less than 2 years) male and female rabbits. Aged female rabbits (3-5+ years) and females aged 2-3 years showed significant augmentation of fever only after pretreatment plus acute injection of antiserum. A single ICV injection of MSH (200 ng) reduced fever in all groups with the greatest antipyretic effect in the aged females. The results indicate that while aged rabbits have an increased antipyretic response to central MSH, binding of the endogenous peptide does not result in marked increases in fever in these animals. Thus, whereas a change in central MSH sensitivity may contribute to reduced fever in aged homeotherms, a reduction in central pyrogen receptors appears to be the most parsimonious explanation.

Concentration of melanocyte stimulating hormone (MSH) within specific brain regions in aged squirrel monkeys

The concentration of MSH per unit protein is reduced on average in several sites within the brains of aged squirrel monkeys. This decrease may account for alterations in CNS functions mediated via MSH but perhaps does not account for reduced fever in these aged subhuman primates.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC and related agents: II

Antipyretics, in particular acetaminophen, aspirin and ibuprofen, constitute the single most important class of drugs used therapeutically for an effect on body temperature. Hallucinogens exert prominent actions on the central nervous system, and it is not surprising that, like so many other centrally-acting agents, they too often affect temperature. This compilation primarily covers the considerable amount of data published from 1981 through 1985 on the interactions of these drugs and thermoregulation, but data from many earlier papers not included in a previous compilation are also tabulated. The effects of agents not classically considered as antipyretics on temperatures of febrile subjects are also covered. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent.

Neuropeptide regulation of interleukin-1 activities. Capacity of alpha-melanocyte stimulating hormone to inhibit interleukin-1-inducible responses in vivo and in vitro exhibits target cell selectivity

alpha-Melanocyte stimulating hormone (alpha-MSH), a 13 amino acid neuropeptide produced by the pituitary gland, was found to markedly inhibit the capacity of exogenously administered interleukin-1 (IL-1) to stimulate the enhanced synthesis of acute-phase proteins and induce neutrophilia in vivo. The administration of ACTH or glucocorticosteroids lacked most of these direct IL-1 inhibitory properties. Therefore, in addition to the previously reported antipyretic action of alpha-MSH, this hormone can also inhibit two other known IL-1 sensitive cellular targets in vivo. Further, alpha-MSH was incapable of modifying the comitogenic influence of IL-1 on murine thymocytes or on an IL-1 responsive T-cell line. These findings suggest a target cell specificity to the IL-1 inhibitory activities of alpha-MSH and fail to support the hypothesis that alpha-MSH functions through competitive inhibition of specific cellular receptors for IL-1.

Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.

Intravenous alpha-MSH reduces fever in the squirrel monkey

alpha-MSH reduces fever in rabbits when administered IV, ICV, or by gavage; however, the applicability of this finding to higher species, specifically to primates, has not been determined. In this study, we chose the squirrel monkey as an appropriate primate model since it responds reliably to peripheral administration of bacterial endotoxins that cause fever in man. From pilot studies, doses of S. typhosa endotoxin necessary to produce maximum fever and doses of alpha-MSH which did not cause hypothermia were determined for each animal. In the main experiments endotoxin was given via an indwelling catheter in the saphenous vein, followed by alpha-MSH injections when the rectal temperature increased 0.3 degrees C. alpha-MSH (100-400 micrograms) reduced the area under the fever curve an average of 50.0%, but had no effect on afebrile temperature. Molar equivalent amounts of the antipyretic drug acetaminophen had little effect on fever. These findings support the idea, based on research on rabbits, that alpha-MSH has a role in central modulation of fever.

Effects of massive doses of alpha-MSH on thermoregulation in the rabbit

alpha-MSH-related compounds may prove to be clinically useful antipyretics since the parent peptide is extremely potent in reducing fever, it is effective when given orally, and it neither stimulates corticosteroid activity nor has marked melanotropic effects in man. To determine whether or in what doses alpha-MSH might cause harmful side-effects, we injected doses greatly exceeding those required to reduce fever into a lateral cerebral ventricle of afebrile rabbits. One hundred to seven hundred and fifty micrograms alpha-MSH caused large and prolonged reductions in body temperature and the dose-response relation was bell-shaped for both magnitude and duration. These doses caused no apparent injury to the animals. One mg alpha-MSH elicited hyperthermic responses that were variable in magnitude and duration. Animals that had previously received large doses of alpha-MSH (greater than or equal to 100 micrograms) did not develop hyperthermia, even when given 2 mg, indicating an acquired tolerance to this hyperthermic action of alpha-MSH. All animals, tolerant or previously uninjected, showed symptoms with doses greater than or equal to 1 mg alpha-MSH that included: increased salivation, agitation, ataxia, respiratory distress, and death (in 30% of the animals); those that recovered from these large doses resumed outwardly healthy appearance and behavior. Although alpha-MSH is toxic when given centrally in large doses, the 5000-fold difference between antipyretic and toxic doses indicates a wide safety margin should this peptide be used clinically as an antipyretic drug.

Antipyretic activity of a potent alpha-MSH analog

[Nle4,D-Phe7]-alpha-MSH has exceptional potency in certain biological assays of alpha-MSH activity such as skin darkening in frogs. However, this analog was equipotent to alpha-MSH in induction of grooming in the rat and had opposite effects on the performance of a visual discrimination task. These results led to the suggestion that distinct differences may exist between the melanocyte and CNS receptors for alpha-MSH. We determined the antipyretic and hypothermic potencies of centrally and peripherally administered [Nle4,D-Phe7]-alpha-MSH, relative to those of alpha-MSH, in the rabbit. Central injections of 40 and 80 ng of [Nle4,D-Phe7]-alpha-MSH caused hypothermia in afebrile rabbits, whereas 20 and 10 ng, which had no effect on afebrile body temperature, caused greater than 40% reduction in leukocytic pyrogen-induced fever. These results indicate that this analog is approximately 10 times more potent in reducing fever than alpha-MSH, making it the most potent antipyretic substance yet described. In contrast, IV administration of 16 micrograms of the analog, an extremely large dose relative to established antipyretic doses of alpha-MSH, elicited weak, variable responses. Since this analog is said to be resistant to degradation by serum enzymes, the contrast between the effects of central and peripheral administration may reflect a limited ability of the analog to cross the blood brain barrier when given IV. Our results do not suggest any distinct differences between the melanocyte receptors for alpha-MSH and those involved with CNS control of temperature. The marked central potency of [Nle4,D-Phe7]-alpha-MSH could result from an increased duration of action and/or a greater affinity for central receptor sites relative to alpha-MSH.

Analysis of the antipyretic action of alpha-melanocyte-stimulating hormone in rabbits

alpha-Melanocyte-stimulating hormone (alpha-MSH) or paracetamol was injected into a lateral cerebral ventricle (I.C.V.) of rabbits with elevations in rectal temperature induced by sodium arachidonate (I.C.V.), prostaglandin E2 (I.C.V.) or leucocytic pyrogen (I.V.). alpha-MSH (200 ng) was more effective than paracetamol (0.5 mg) in reducing fever caused by leucocytic pyrogen, but it did not alter hyperthermia induced by sodium arachidonate. In contrast, paracetamol reduced hyperthermic responses to arachidonate by about 70%. Neither alpha-MSH nor paracetamol affected hyperthermic responses to prostaglandin E2. The doses of alpha-MSH and paracetamol used in these experiments did not interfere with thermoregulation in a cold environment (10 degrees C). We conclude (1) that alpha-MSH and paracetamol differ in their central mechanism of antipyresis or (2) that inhibition of arachidonic acid metabolism by paracetamol is not requisite for its antipyretic effect, in which case central release of alpha-MSH may mediate the antipyretic effect of paracetamol.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents: II

This survey begins a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1978, but data from many earlier papers are also tabulated.

Effect of alpha-MSH 11-13 (lysine-proline-valine) on fever in the rabbit

In previous experiments, alpha-MSH (1-13) and ACTH (1-24), which contains the alpha-MSH 1-13 amino acid sequence, were found to reduce fever after central and peripheral administration of low, non-hypothermic doses. Shorter molecules, including alpha-MSH 1-10, had no effect. The idea that the 11-13 amino acid sequence is important to the effect of the parent molecule was tested by giving lysine-proline-valine both centrally and peripherally to rabbits made febrile by IV administration of leukocytic pyrogen. The tripeptide reduced fever after both central (0.5-2.0 mg) and peripheral (2-200 mg) administration. It appears that the 11-13 sequence is part of the message sequence of alpha-MSH with regard to antipyretic activity. However, the lower potency relative to that of the parent molecule suggests that other portions of the molecule are essential to full expression of the antipyretic effect.

Antipyretic effect of centrally administered CRF

CRF injected into the third cerebral ventricle (0.5-2.5 micrograms) caused dose-related reductions in fever induced in rabbits by IV administration of leukocytic pyrogen. Control injections of CRF when the same animals were afebrile did not alter normal body temperature. Intravenous injections of 5 and 20 micrograms CRF, doses known to release ACTH and corticosteroids into the bloodstream in other species, did not reduce fever. CRF injected into the cerebral ventricles may be antipyretic per se, or it may reduce fever by virtue of central release of the antipyretic peptides ACTH and alpha-MSH.

Brain peptides: what, where, and why?

Within the past decade, a large number of peptides have been described within the vertebrate central nervous system. Some of these peptides were previously known to be present in nonneural vertebrate tissues, as well as in lower species, in which they may serve as primitive elements of intercellular communication prior to the development of neuronal or endocrine systems. In vertebrates, these peptides are thought to have neurotransmitter or neuromodulatory roles and appear to be involved in the regulation of a number of homeostatic systems, although the mechanisms of their actions are still unclear.

Beta-endorphin: effect on thermoregulation in aged monkeys

In previous experiments small doses of the opiate morphine produced greater hyperthermia in aged than in younger sub-human primates. To test whether this augmented response is due to enhanced sensitivity of CNS opioid receptors with age, beta-endorphin (0.625-5 micrograms), an endogenous opioid peptide, was injected into the lateral cerebral ventricle (ICV) of young (less than 9 years) and aged (greater than 9 years) squirrel monkeys. Significantly greater hyperthermias developed in the older primates after each dose. In the aged monkeys, all but the smallest dose increased core temperature about 1.5 degrees C within 1 hr after injection. Mean rectal temperature in the younger animals rose 0.5-0.7 degrees after all but the largest dose (1-1.5 degrees C rise). Both groups maintained an elevated body temperature after central beta-endorphin throughout the 5 hr recording period. 1.25 micrograms beta-endorphin given ICV in a hot environment (30 degrees C) caused greater hyperthermia in older animals. This dose given in the cold (18 degrees C) caused large changes in temperature of the aged monkeys, either hyperthermia or marked decreases, whereas the young primates developed only moderate rises in body temperature. The same dose of morphine sulfate (1.25 micrograms) ICV produced similar changes in core temperature in the two age groups in each ambient temperature. These results indicate that: (1) stimulation of CNS opioid receptors influences thermoregulation and (2) aging increases responsiveness to such stimulation.

Antipyretic potency of centrally administered alpha-melanocyte stimulating hormone

Centrally administered alpha-melanocyte stimulating hormone is much more potent in reducing fever than the widely used antipyretic acetaminophen. This finding supports the hypothesis that the endogenous neuropeptide has a role in the limitation of fever and suggests that it may be clinically useful as an antipyretic.

alpha-MSH injected into the septal region reduces fever in rabbits

In previous research the concentration of alpha-MSH within the septal region of rabbits increased with fever. This finding raises the possibility that the septal concentration of this peptide, which reduces fever when given both peripherally and intracerebroventricularly, is important to limitation of fever. To test this idea, rabbits with cannulas in the septal region were made febrile by IV injections of leukocytic pyrogen (LP). Injection of alpha-MSH (1 microgram bilaterally) into the septal region did reduce fever, consistent with the idea that the increase in septal alpha-MSH concentration which occurs naturally in fever limits the febrile response. We also noted late rises in body temperature when experimental and control septal injections were given close together in time. These increases in temperature were similar to those known to occur after injections into the primary temperature control in the PO/AH region. This commonality further strengthens the possibility that septal neurons are important to central modulation of body temperature.