Endogenous antipyretics

Survey of knowledge, practice, and associated factors toward home management of childhood fever among parents visiting Gondar health facilities in 2022

Background

Fever is a typical symptom of many sicknesses, but for children under the age of five, fever can have devastating consequences and represents a source of worry for parents. To the best of our knowledge, no research on home management of fever in children has been conducted in Ethiopia. We aimed to assess knowledge, practices, and associated factors towards home management of childhood fever among parents visiting Gondar Town health facilities in 2022.

Method

This multicenter institutional-based cross-sectional study was conducted in Gondar public health facilities from June 1st-June 30th, 2022. Participants were fathers and mothers of children aged 0-5 years. A stratified random sampling technique was used. Data were collected through face-to-face interviews using a pretested structured questionnaire.

Results

Approximately, 40.2% (95% CI: 35.5%, 45.2%) of parents had good knowledge and only 12.8% (95% CI: 9.7-15.8) of parents practiced home fever management. Being married [Adjusted odds ratio [(AOR) = 2.1 (1.2, 3.2)], having a primary or higher level of education [AOR = 2.4 (1.17, 4.9)] [AOR = 2.0 (1.02-4.6)], respectively, and number of children [AOR = 1.8 (1.63, 2.03)] were factors associated with parental knowledge. Likewise, being married [AOR = 3.05 (2.27.50-3.83)], receiving counseling from health care providers [AOR = 2.12 (1.53-3.32)], and being male [AOR = 2.03 (1.50-3.00)] were significant predictors of practice.

Conclusion

Inadequate levels of knowledge and numerous irrational practices related to home fever management were predominant among parents, which needs to be addressed. Evidence-based health education is essential for parents to enhance their level of knowledge and practice to effectively treat fever at home.

Current State of Knowledge on the Definition, Pathophysiology, Etiology, Outcomes, and Management of Fever in the Intensive Care Unit

Fever-an elevated body temperature-is a prominent feature of a wide range of disease conditions and is a common finding in intensive care, affecting up to 70% of patients in the intensive care unit (ICU). The causes of fever in the ICU are multifactorial, and it can be due to a number of infective and noninfective etiologies. The production of fever represents a complex physiological, adaptive host response that is beneficial for host defense and survival but can be maladaptive and harmful if left unabated. Despite any cause, fever is associated with a wide range of cellular, local, and systemic effects, including multiorgan dysfunction, systemic inflammation, poor neurological recovery, and an increased risk of mortality. This narrative review presents the current state-of-the-art knowledge on the definition, pathophysiology, etiology, and outcomes of fever in the ICU and highlights evidence-based findings regarding the management of fever in the intensive care setting.

Electrolyte abnormalities and stress dosing predict illness-related hospitalizations among infants and toddlers with congenital adrenal hyperplasia

OBJECTIVE

Infants and toddlers with classical congenital adrenal hyperplasia (CAH) are at high risk for morbidity/mortality arising from life-threatening adrenal crisis. Management of acute illnesses in CAH requires an understanding of factors leading to emergency department (ED) visits and hospitalizations in the first few years of life. We, therefore, examined adrenal crisis at prehospital and ED stages of illness in young children with CAH as they related to medical outcomes.

PATIENTS AND DESIGN

Retrospective cohort study of 39 children with CAH due to 21-hydroxylase deficiency (0-4 years of age) and 27 age-matched controls.

MEASUREMENTS

ED visit, acute illness symptoms (fever, vomiting, diarrhoea) and other characteristics (hospitalizations, administration of stress-dose hydrocortisone, electrolyte abnormalities).

RESULTS

CAH infants and toddlers had significantly higher rates of ED visits (0.50 [0.25-0.88] per person-year) than controls (0 [0-0] per person-year; p < .001). Moreover, CAH children under 6 months old had significantly higher rates of ED visits compared with older ages. Only 50% (51/102) of illness-related ED visits in CAH children were preceded by the administration of either oral (46/51) or intramuscular (11/51) stress dosing by parents. A total of 10.8% of ED visits resulted in hospital admission. Controlling for age and 17-hydroxyprogesterone at diagnosis, electrolyte abnormalities and administration of parenteral hydrocortisone in the ED significantly predicted hospital admission. Receiving a hydrocortisone injection before the ED was a significant predictor of having electrolyte abnormalities.

CONCLUSIONS

Infants and toddlers with classical CAH are at high risk for acute illness and hospitalizations and often do not receive adequate stress dosing before the ED.

Physiologic effects of stress dose corticosteroids in in-hospital cardiac arrest (CORTICA): A randomized clinical trial

Aim

Postresuscitation hemodynamics are associated with hospital mortality/functional outcome. We sought to determine whether low-dose steroids started during and continued after cardiopulmonary resuscitation (CPR) affect postresuscitation hemodynamics and other physiological variables in vasopressor-requiring, in-hospital cardiac arrest.

Methods

We conducted a two-center, randomized, double-blind trial of patients with adrenaline (epinephrine)-requiring cardiac arrest. Patients were randomized to receive either methylprednisolone 40 mg (steroids group) or normal saline-placebo (control group) during the first CPR cycle post-enrollment. Postresuscitation shock was treated with hydrocortisone 240 mg daily for 7 days maximum and gradual taper (steroids group), or saline-placebo (control group). Primary outcomes were arterial pressure and central-venous oxygen saturation (ScvO₂) within 72 hours post-ROSC.

Results

Eighty nine of 98 controls and 80 of 86 steroids group patients with ROSC were treated as randomized. Primary outcome data were collected from 100 patients with ROSC (control, n = 54; steroids, n = 46). In intention-to-treat mixed-model analyses, there was no significant effect of group on arterial pressure, marginal mean (95% confidence interval) for mean arterial pressure, steroids vs. control: 74 (68–80) vs. 72 (66–79) mmHg] and ScvO₂ [71 (68–75)% vs. 69 (65–73)%], cardiac index [2.8 (2.5–3.1) vs. 2.9 (2.5–3.2) L/min/m²], and serum cytokine concentrations [e.g. interleukin-6, 89.1 (42.8–133.9) vs. 75.7 (52.1–152.3) pg/mL] determined within 72 hours post-ROSC (P = 0.12–0.86). There was no between-group difference in body temperature, echocardiographic variables, prefrontal blood flow index/cerebral autoregulation, organ failure-free days, and hazard for poor in-hospital/functional outcome, and adverse events (P = 0.08–>0.99).

Conclusions

Our results do not support the use of low-dose corticosteroids in in-hospital cardiac arrest.

Trial Registration:ClinicalTrials.gov number: NCT02790788 (https://www.clinicaltrials.gov).

Comprehensive biology of antipyretic pathways

Pyrogens, the fever inducing substances accidently enter into a human body through contamination from medical or pharmaceutical products may create mild to severe complications including septicaemia and shocking syndromes. To avoid such drastic situations all the pharmaceuticals and medical devices are analysed for presence of pyrogens prior to their release into market. The entry of exogenous pyrogens like bacterial endotoxins induces the release of endogenous pyrogens or inflammatory cytokines that activate immune system to defend against these pathogens. Generation of heat is considered as one of the important defence mechanism of body achieved through receptor mediated interaction of endogenous pyrogens at the thermoregulatory centre of hypothalamus. However, uncontrolled fever and febrile reaction may cause lethal effects to the subject itself. So a well sophistically functioning antipyretic mechanism is necessary to achieve thermoregulation. The coordinated interaction of antipyretic cytokines and other mediators are active in human immune system which play a crucial role in maintaining thermal homeostasis. The multiple interacting antipyretic signals and their mechanism are the major subjects of this review.

Effects of Trypanosoma brucei brucei infection and diminazene aceturate administration on the blood pressure, heart rate, and temperature of Wistar albino rats

BACKGROUND

This study was carried out to determine the blood pressure changes in experimentally Trypanosoma brucei brucei-infected Wistar albino rats and diminazene aceturate-treated rats.

METHODS

Twenty-four rats were purchased and divided into four groups consisting of six rats each. Control group (CON) received 0.5 mL of distilled water, i.m., infected but not treated group (INF) received 2×106 trypanosome/mL i.m., infected but diminazene aceturate-treated group (INFDIM) received 2×106 trypanosome/mL, 3.5 mg/kg, i.m.) and non-infected but diminazene aceturate-treated group (DIM) received 3.5 mg/kg, i.m. and served as negative control. The blood pressures were measured using a CODA 2® non-invasive blood pressure monitor (Kent Scientific, USA). The results were compiled and statistical analysis was done with significance set at p≥0.05.

RESULTS

The values of the blood pressure readings of the Trypanosoma-infected INF (137.0±2.0 mmHg) and diminazene-treated rats INFDIM (125.0±7.5 mmHg) when compared to the control group (168.0±3.0 mmHg) were significantly lower (p≤0.05) at the end of day 7. The heart rate was also significantly reduced in the INF (403.5±1.5 beats/min) and DIM (445.0±24 beats/min) groups of rats when compared with the control group (613.0±2.0 beats/min) at the end of day 8.

CONCLUSION

The findings indicate the significant reduction in blood pressure and heart rates during Trypanosoma brucei brucei infection and with diminazene aceturate administration. Hence, caution should be exercised when treating trypanosome-infected patients with diminazene aceturate.

Sports participation for young athletes with medical conditions: Seizure disorder, infections and single organs

Organized and recreational sports have been shown to be an important part of growth and development in children, adolescents and young adults. In addition to the health benefits of increased physical activity, sports also provide social benefits. Pediatricians play an important role in determining if young athletescan participate in various sports and the proper equipment or precautions that are necessary. This review provides information on sports participation for athletes with specific health considerations, such as: febrile illnesses, solitary organs, seizures, and skin infections.

H89 dihydrochloride hydrate and calphostin C lower the body temperature through TRPV1

The transient receptor potential vanilloid (TRPV1) serves as a negative regulator of body temperature, and during fever conditions its expression can lead to a decrease in temperature. TRPV1 is regulated by a variety of enzymes; however, it is currently unclear whether the regulation of TRPV1 phosphorylation may serve a role in the increase in TRPV1 expression during fever. In the present study, using an in vivo experimental method, rat brain ventricles were injected with the protein kinase A (PKA) antagonist, H89, and the protein kinase C (PKC) antagonist, calphostin C, and fever was induced using lipopolysaccharide (LPS) in order to detect the expression of TRPV1 and phosphorylated (p-)TRPV1, the intracellular Ca²⁺ concentration [(Ca²⁺⁾_i] of hypothalami and rat body temperature. The results demonstrated that following the generation of fever using LPS, the expressions of TRPV1 and p-TRPV1, and hypothalamic [Ca²⁺]_i markedly increased. In addition, following an injection with the PKA or PKC antagonist, the temperature increased further due to the inhibition of p-TRPV1. Thus, it was hypothesized that PKA and PKC may be involved in TRPV1 phosphorylation, resulting in a temperature reduction during LPS-induced fever conditions.

Behavioral hypothermia of a domesticated lizard under treatment of the hypometabolic agent 3-iodothyronamine

Ectothermic animals rely on behavioral thermoregulation due to low capacity of heat production and storage. Previously, lizards were shown to achieve ‘fever’ during microbial infection by increasing their preferred body temperature (PBT) behaviorally, thereby attaining a relatively high survival rate. The purpose of this study was to investigate whether domesticated lizards pursued ‘behavioral hypothermia’ induced by a hypometabolic agent 3-iodothyronamine (T1AM). We found that treatment with 8.0 mg/kg T1AM caused a lizard species, the leopard gecko (Eublepharis macularius), to decrease its ventilation and oxygen consumption rates 0.64- and 0.76-fold, respectively, compared to those of the control (P<0.05). The lizards, habituated at an ambient temperature of 30 ± 0.5°C, also showed a significant decrease in the PBT range over a freely accessible thermal gradient between 5°C and 45°C. The upper limit of the PBT in the treated lizards lowered from 31.9°C to 30.6°C, and the lower limit from 29.5°C to 26.3°C (P<0.001). These findings demonstrate that the treated lizards pursued behavioral hypothermia in conjunction with hypoventilation and hypometabolism. Because prior studies reported a similar hypometabolic response in T1AM-injected laboratory mice, the domesticated lizards, as a part of the vertebrate phylogeny, may be a useful laboratory model for biological and pharmacological researches such as drug potency test.

Mechanisms of fever production and lysis: lessons from experimental LPS fever

Fever is a cardinal symptom of infectious or inflammatory insults, but it can also arise from noninfectious causes. The fever-inducing agent that has been used most frequently in experimental studies designed to characterize the physiological, immunological and neuroendocrine processes and to identify the neuronal circuits that underlie the manifestation of the febrile response is lipopolysaccharide (LPS). Our knowledge of the mechanisms of fever production and lysis is largely based on this model. Fever is usually initiated in the periphery of the challenged host by the immediate activation of the innate immune system by LPS, specifically of the complement (C) cascade and Toll-like receptors. The first results in the immediate generation of the C component C5a and the subsequent rapid production of prostaglandin E2 (PGE2). The second, occurring after some delay, induces the further production of PGE2 by induction of its synthesizing enzymes and transcription and translation of proinflammatory cytokines. The Kupffer cells (Kc) of the liver seem to be essential for these initial processes. The subsequent transfer of the pyrogenic message from the periphery to the brain is achieved by neuronal and humoral mechanisms. These pathways subserve the genesis of early (neuronal signals) and late (humoral signals) phases of the characteristically biphasic febrile response to LPS. During the course of fever, counterinflammatory factors, "endogenous antipyretics," are elaborated peripherally and centrally to limit fever in strength and duration. The multiple interacting pro- and antipyretic signals and their mechanistic effects that underlie endotoxic fever are the subjects of this review.

Incidence rate of fluoroquinolone-resistant gram-negative rod bacteremia among allogeneic hematopoietic cell transplantation patients during an era of levofloxacin prophylaxis

There are concerns that emerging resistance to fluoroquinolones (FQ) may be leading to increasing rates of gram-negative rod (GNR) bacteremia in hematopoietic cell transplant (HCT) recipients. We set out to describe time trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia in HCT recipients during an era of levofloxacin prophylaxis. We conducted a longitudinal retrospective study of adults undergoing allogeneic HCT between 2003 and 2012 at the Seattle Cancer Care Alliance (SCCA). Annual trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia through 100 days after transplantation were assessed using Poisson regression. Cox proportional hazards regression was used to compare 30-day mortality between patients with FQ-resistant and those with FQ-sensitive GNR bacteremia. Of the 2306 patients included in this cohort, 280 (12.1%) had GNR bacteremia. The incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia increased from 2003 to 2009 and decreased afterwards; however, the overall annual trends were not significant (incidence rate ratio [IRR], 1.01; 95% confidence interval [CI], .98 to 1.05; IRR, 1.01; 95% CI, .95 to 1.08, respectively). FQ-resistant GNR bacteremia was associated with increased mortality compared with FQ-sensitive GNR bacteremia, even after adjustment for underlying disease severity, conditioning regimen, and age at transplantation (hazard ratio, 2.11; 95% CI, 1.06 to 4.23). On average, rates of FQ-resistant GNR bacteremia have not significantly changed over 10 years of FQ prophylaxis, although FQ-resistant GNR bacteremia is associated with increased mortality compared with FQ-sensitive GNR bacteremia.

Correlation Between Body Temperature and Survival Rate in Patients With Hospital-Acquired Bacteremia

Background:

Fever is a complex and major sign of a patient’s acute response to infection. However, analysis of the risks and benefits associated with the change in body temperature of an infected host remains controversial.

Objective:

To examine the relationship between the intensity of the change in body temperature and the mortality of patients with hospital-acquired bacteremia.

Design:

A prospective observational study.

Method:

Subjects were hospitalized adult patients who developed clinical signs of infection 48 hr or more after admission and had documented bacterial growth in blood culture. The maximum body temperature (maxTe) during the early period of infection measurements (i.e., the day before, the day of, and 2 days after the day of blood culture) was used to indicate the intensity of the body temperature response. Patients were categorized as discharged alive or died in hospital. Cox regression analysis was employed to analyze the data.

Results:

The cohort consisted of 502 subjects. The mean maxTe of subjects was 38.6°C, and 14.9% had a maxTe lower than 38.0°C. The in-hospital mortality rate was 18.9%. The highest in-hospital mortality was found in subjects with a maxTe lower than 38°C (30.7%). Multivariate Cox regression analysis determined that the maxTe and the severity of comorbidity are the two variables associated with in-hospital mortality.

Conclusions:

Lack of a robust febrile response may be associated with greater risk of mortality in patients with bacteremia. Clinicians must be vigilant in identifying patients at risk for a blunted febrile response to bacteremia for more intensive monitoring.

Modeling the inflammatory response in the hypothalamus ensuing heat stroke: iterative cycle of model calibration, identifiability analysis, experimental design and data collection

Heat Stroke (HS) is a life-threatening illness caused by prolonged exposure to heat that causes severe hyperthermia and nervous system abnormalities. The long term consequences of HS are poorly understood and deeper insight is required to find possible treatment strategies. Elevated pro- and anti-inflammatory cytokines during HS recovery suggest to play a major role in the immune response. In this study, we developed a mathematical model to understand the interactions and dynamics of cytokines in the hypothalamus, the main thermoregulatory center in the brain. Uncertainty and identifiability analysis of the calibrated model parameters revealed non-identifiable parameters due to the limited amount of data. To overcome the lack of identifiability of the parameters, an iterative cycle of optimal experimental design, data collection, re-calibration and model reduction was applied and further informative experiments were suggested. Additionally, a new method of approximating the prior distribution of the parameters for Bayesian optimal experimental design based on the profile likelihood is presented.

Astrocytes: new targets of melanocortin 4 receptor actions

Astrocytes exert a wide variety of functions with paramount importance in brain physiology. After injury or infection, astrocytes become reactive and they respond by producing a variety of inflammatory mediators that help maintain brain homeostasis. Loss of astrocyte functions as well as their excessive activation can contribute to disease processes; thus, it is important to modulate reactive astrocyte response. Melanocortins are peptides with well-recognized anti-inflammatory and neuroprotective activity. Although melanocortin efficacy was shown in systemic models of inflammatory disease, mechanisms involved in their effects have not yet been fully elucidated. Central anti-inflammatory effects of melanocortins and their mechanisms are even less well known, and, in particular, the effects of melanocortins in glial cells are poorly understood. Of the five known melanocortin receptors (MCRs), only subtype 4 is present in astrocytes. MC4R has been shown to mediate melanocortin effects on energy homeostasis, reproduction, inflammation, and neuroprotection and, recently, to modulate astrocyte functions. In this review, we will describe MC4R involvement in anti-inflammatory, anorexigenic, and anti-apoptotic effects of melanocortins in the brain. We will highlight MC4R action in astrocytes and discuss their possible mechanisms of action. Melanocortin effects on astrocytes provide a new means of treating inflammation, obesity, and neurodegeneration, making them attractive targets for therapeutic interventions in the CNS.

Altered cognitive-emotional behavior in early experimental autoimmune encephalitis--cytokine and hormonal correlates

Multiple sclerosis (MS) is often associated with co-morbid behavioural and cognitive impairments; however the presence of these symptoms does not necessarily correlate with neurological damage. This suggests that an alternate mechanism may subserve these impairments relative to motor deficits. We investigated whether these abnormalities could be studied in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. In myelin oligodendrocyte glycoprotein peptide (MOG35-55)-induced EAE mice, no motor deficits were observed until d9 after immunization. This enabled us to carry out a series of neurobehavioral tests during the presymptomatic stage, between d6 and d8 post-immunization. EAE mice spent more time in the outer zone in an open field test and in the closed arms of an elevated plus maze and, showed decreased latency for immobility in the tail suspension and forced swim tests and reduced social interaction compared with controls. These results are indicative of anxiety- and depression- like behavior. In addition, EAE mice appeared to exhibit memory impairment compared to controls based on their reduced time spent in the target quadrant in the Morris water maze and their faster memory extinction in the fear conditioning test. No demyelination, microglial activation or astrogliosis was observed in the brain at this early stage. Transcript analysis by RT-PCR from d6 to d8 brain revealed elevated interleukin (IL)-1β and TNF-α in the hypothalamus but not in the amygdala or hippocampus of EAE mice. Lastly, plasma corticosterone levels increased in EAE mice compared to controls. In conclusion, emotional and cognitive deficits are observed in EAE prior to demyelination and are associated with elevated IL-1β and TNF-α in the hypothalamus and changes in the hypothalamic-pituitary-adrenal axis.

Fever, fever patterns and diseases called 'fever'--a review

Fever is a prominent feature of disease since antiquity. The febrile response is orchestrated by the central nervous system through endocrine, neurological, immunological and behavioural mechanisms. Other than a regulated rise in body temperature, fever is often accompanied by various sickness behaviours, changes in metabolic and physiological characteristics of body systems and alterations in immune responses. Fever and the febrile response, therefore, remain significant contributors to the pathogenesis, clinical presentation and outcome of many illnesses and diseases. This review highlights the pathophysiology of the febrile response and describes the fever types and patterns, including their clinical significance. The various medical illnesses called "fever" are also listed and the origins of their appellations discussed.

Dorsomedial hypothalamus mediates autonomic, neuroendocrine, and locomotor responses evoked from the medial preoptic area

Previous studies suggest that sympathetic responses evoked from the preoptic area in anesthetized rats require activation of neurons in the dorsomedial hypothalamus. Disinhibition of neurons in the dorsomedial hypothalamus in conscious rats produces physiological and behavioral changes resembling those evoked by microinjection of muscimol, a GABA(A) receptor agonist and neuronal inhibitor, into the medial preoptic area. We tested the hypothesis that all of these effects evoked from the medial preoptic area are mediated through neurons in the dorsomedial hypothalamus by assessing the effect of bilateral microinjection of muscimol into the DMH on these changes. After injection of vehicle into the dorsomedial hypothalamus, injection of muscimol into the medial preoptic area elicited marked increases in heart rate, arterial pressure, body temperature, plasma ACTH, and locomotor activity and also increased c-Fos expression in the hypothalamic paraventricular nucleus, a region known to control the release of ACTH from the adenohypophysis. Prior bilateral microinjection of muscimol into the dorsomedial hypothalamus produced a modest depression of baseline heart rate and body temperature but completely abolished all changes evoked from the medial preoptic area. Microinjection of muscimol just anterior to the dorsomedial hypothalamus had no effect on autonomic and neuroendocrine changes evoked from the medial preoptic area. Thus, activity of neurons in the dorsomedial hypothalamus mediates a diverse array of physiological and behavioral responses elicited from the medial preoptic area, suggesting that the latter region represents an important source of inhibitory tone to key neurons in the dorsomedial hypothalamus.

Role of alpha-melanocyte stimulating hormone and melanocortin 4 receptor in brain inflammation

Inflammatory processes contribute widely to the development of neurodegenerative diseases. The expression of many inflammatory mediators was found to be increased in central nervous system (CNS) disorders suggesting that these molecules are major contributors to neuronal damage. Melanocortins are neuropeptides that have been implicated in a wide range of physiological processes. The melanocortin alpha-melanocyte stimulating hormone (alpha-MSH) has pleiotropic functions and exerts potent anti-inflammatory actions by antagonizing the effects of pro-inflammatory cytokines and by decreasing important inflammatory mediators. Five subtypes of melanocortin receptors (MC1R-MC5R) have been identified. Of these, the MC4 receptor is expressed predominantly throughout the CNS. Evidence of effectiveness of selective MC4R agonists in modulating inflammatory processes and their low toxicity suggest that these molecules may be useful in the treatment of CNS disorders with an inflammatory component. This review describes the involvement of the MC4R in central anti-inflammatory effects of melanocortins and discusses the potential value of MC4R agonists for the treatment of inflammatory-related disorders.

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.

Central and peripheral neuroimmune responses: hyporesponsiveness during pregnancy

There are periods in the life of a healthy animal (including humans) when the febrile response to an immune challenge is suppressed. One such period is during late pregnancy, particularly around the time of parturition. In the 30 or so years since this 'febrile hyporesponsiveness' was first noted, much work has been done to investigate the mechanisms and adaptive significance of this phenomenon. In this review we present some insight into how and why the body deliberately re-programmes itself to develop smaller fevers in response to an immune challenge and therefore to be potentially less successful at fighting infection.

Endotoxic fever: New concepts of its regulation suggest new approaches to its management

Endotoxic fever is regulated by endogenous factors that provide pro- and anti-pyretic signals at different points along the febrigenic pathway, from the periphery to the brain. Current evidence indicates that the febrile response to invading Gram-negative bacteria and their products is initiated upon their arrival in the liver via the circulation and their uptake by Kupffer cells (Kc). These pathogens activate the complement cascade on contact, hence generating complement component 5a. It, in turn, very rapidly stimulates Kc to release prostaglandin (PG)E2. Pyrogenic cytokines (TNF-alpha, etc.) are produced later and are no longer considered to be the immediate triggers of fever. The Kc-generated PGE2 either (1) may be transported by the bloodstream to the ventromedial preoptic-anterior hypothalamus (POA, the locus of the temperature-regulating center), presumptively diffusing into it and acting on thermoregulatory neurons; PGE2 is thus taken to be the final, central fever mediator. Or (2) it may activate hepatic vagal afferents projecting to the medulla oblongata, thence to the POA via the ventral noradrenergic bundle. Norepinephrine consequently secreted stimulates alpha1-adrenoceptors on thermoregulatory neurons, rapidly evoking an initial rise in core temperature (Tc) not associated with any change in POA PGE2; this neural, PGE2-independent signaling pathway is quicker than the blood-borne route. Elevated POA PGE2 and a secondary Tc rise occur later, consequent to alpha2 stimulation. Endogenous counter-regulatory factors are also elaborated peripherally and centrally at different points during the course of the febrile response; they are, therefore, anti-pyretic. These multiple interacting pathways are the subject of this review.

Physiology of temperature regulation: comparative aspects

Few environmental factors have a larger influence on animal energetics than temperature, a fact that makes thermoregulation a very important process for survival. In general, endothermic species, i.e., mammals and birds, maintain a constant body temperature (Tb) in fluctuating environmental temperatures using autonomic and behavioural mechanisms. Most of the knowledge on thermoregulatory physiology has emerged from studies using mammalian species, particularly rats. However, studies with all vertebrate groups are essential for a more complete understanding of the mechanisms involved in the regulation of Tb. Ectothermic vertebrates-fish, amphibians and reptiles-thermoregulate essentially by behavioural mechanisms. With few exceptions, both endotherms and ectotherms develop fever (a regulated increase in Tb) in response to exogenous pyrogens, and regulated hypothermia (anapyrexia) in response to hypoxia. This review focuses on the mechanisms, particularly neuromediators and regions in the central nervous system, involved in thermoregulation in vertebrates, in conditions of euthermia, fever and anapyrexia.

Microinjection of prostaglandin E2 and muscimol into the preoptic area in conscious rats: comparison of effects on plasma adrenocorticotrophic hormone (ACTH), body temperature, locomotor activity, and cardiovascular function

The preoptic area (POA) is thought to play an important role in thermoregulation and fever. Local application of prostaglandin E2 (PGE2) to this region elicits increases in core body temperature, heart rate, and plasma levels of adrenocorticotrophic hormone (ACTH). Similar effects on body temperature and heart rate have also been reported after local application of the GABAA receptor agonist muscimol to the preoptic area. The purpose of this study was to assess and compare the effects of microinjection of PGE2 and muscimol into the preoptic area in the same chronically instrumented conscious rats on plasma levels of ACTH. Injection of either PGE2 (150 pmol/100 nL) or muscimol (20 or 80 pmol/100 nL) into the same sites in the preoptic area evoked increases in body temperature, heart rate, blood pressure, and plasma levels of ACTH, while significant increases in locomotor activity were apparent only after muscimol. These data confirm and extend previous findings and support the notion that neurons in the region of the preoptic area exert tonic inhibition on downstream mechanisms capable of increasing the activity of the hypothalamic-pituitary-adrenal (HPA) axis as well as sympathetic thermogenic and cardiac activity.

Acetylcholinesterase inhibitors reduce brain and blood interleukin-1beta production

Overproduction of interleukin-1 within the brain is associated with Alzheimer's disease and other neurological conditions. We report that peripheral administration of the acetylcholinesterase inhibitors tacrine, rivastigmine, neostigmine, or EN101 (an antisense oligonucleotide directed at acetylcholinesterase messenger RNA) to mice significantly attenuated the production of interleukin-1beta in the hippocampus and blood, concomitantly with the reduction in acetylcholinesterase activity. These findings demonstrate that cholinergic enhancement produces central and peripheral antiinflammatory effects and suggest a novel therapeutic mechanism for acetylcholinesterase inhibitors.

Early life immune challenge alters innate immune responses to lipopolysaccharide: implications for host defense as adults

Fever is the most common manifestation of the innate immune response to invading pathogens. Animals prevented from developing fever have increased morbidity and mortality to infection. We now show that early life events can program this innate immune response, in that rats that have been challenged neonatally with the immune stimulant lipopolysaccharide (LPS) have both suppressed febrile responses to LPS as adults and significantly reduced nuclear factor (NF)-kappaB activation in peripheral immune organs. This was associated with reduced levels of proinflammatory cytokines tumor necrosis factor (TNF)-alpha, and interleukin-6 (IL-6) in the plasma after adult LPS challenge, compared with animals that have received saline neonatally. In contrast, adult LPS challenge elicited higher corticosterone levels in the animals that had been treated neonatally with LPS. When this increased corticosterone response was negated by adrenalectomy or by administration of the glucocorticoid receptor antagonist RU-486, both the cytokine and febrile responses were normalized. This study indicates that the innate immune response can be programmed by a neonatal LPS challenge, whereby an amplified hypothalamic-pituitary-adrenal response causes reduced cytokine synthesis and an attenuated febrile response to an adult immune challenge. In light of the importance of fever in the host defense response, these alterations may have deleterious consequences on an individual's ability to combat disease later in life.

Long-term alterations in neuroimmune responses after neonatal exposure to lipopolysaccharide

Fever is an integral part of the host's defense to infection that is orchestrated by the brain. A reduced febrile response is associated with reduced survival. Consequently, we have asked if early life immune exposure will alter febrile and neurochemical responses to immune stress in adulthood. Fourteen-day-old neonatal male rats were given Escherichia coli lipopolysaccharide (LPS) that caused either fever or hypothermia depending on ambient temperature. Control rats were given pyrogen-free saline. Regardless of the presence of neonatal fever, adult animals that had been neonatally exposed to LPS displayed attenuated fevers in response to intraperitoneal LPS but unaltered responses to intraperitoneal interleukin 1beta or intracerebroventricular prostaglandin E(2). The characteristic reduction in activity that accompanies fever was unaltered, however, as a function of neonatal LPS exposure. Treatment of neonates with an antigenically dissimilar LPS (Salmonella enteritidis) was equally effective in reducing adult responses to E. coli LPS, indicating an alteration in the innate immune response. In adults treated as neonates with LPS, basal levels of hypothalamic cyclooxygenase 2 (COX-2), determined by semiquantitative Western blot analysis, were significantly elevated compared with controls. In addition, whereas adult controls responded to LPS with the expected induction of COX-2, adults pretreated neonatally with LPS responded to LPS with a reduction in COX-2. Thus, neonatal LPS can alter CNS-mediated inflammatory responses in adult rats.

A novel antipyretic action of 15-deoxy-Delta12,14-prostaglandin J2 in the rat brain

Fever is an important part of the host defense response, yet fever can be detrimental if it is uncontrolled. We provide the first evidence that 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), an endogenous ligand for peroxisome proliferator-activated receptor gamma (PPARgamma), can attenuate the febrile response to lipopolysaccharide (LPS) in rats via an action on the brain. Furthermore, we show that PPARgamma is expressed in the hypothalamus, an important locus in the brain for fever generation. In addition, 15d-PGJ2 and its synthesizing enzyme (PGD2 synthase) were present in rat cerebrospinal fluid, and their levels were enhanced in response to systemic injection of LPS. The antipyretic effect of 15d-PGJ2 was associated with reduction in LPS-stimulated cyclooxygenase-2 expression in the hypothalamus but not in p44/p42 mitogen-activated protein kinase phosphorylation or in the expression of the PPARgamma. Thus it is likely that there is a parallel induction of an endogenous prostanoid pathway in the brain capable of limiting deleterious actions of the proinflammatory prostaglandin E2-dependent pathway.

Roles of the melanocortin-4 receptor in antipyretic and hyperthermic actions of centrally administered α-MSH

Activation of central melanocortin receptors (MCR) inhibits fever but can also stimulate thermogenesis, and the mechanisms involved are unknown. To determine whether the long-recognized antipyretic effect of exogenous alpha-MSH is mediated by the melanocortin-4 receptor (MC4R), and what thermoeffector systems are involved, we tested the effects of intracerebroventricular (i.c.v.) injection of alpha-MSH on lipopolysaccharide (LPS, 30 microg/kg i.p.)-induced fever in rats, in the presence and absence of the selective MC4R antagonist HS014. Treatment with alpha-MSH (1 microg, i.c.v.) suppressed LPS-induced increases in core body temperature (Tc), whereas a lower dose (300 ng) was ineffective. Nevertheless, both alpha-MSH doses effectively inhibited LPS-induced peripheral vasoconstriction, the principal heat-conserving thermoeffector, as determined by changes in tail skin temperature (Tsk). This implies that the net antipyretic effect of alpha-MSH cannot be accounted for solely by modulation of heat loss effectors, but also involves other mechanisms. Surprisingly, central MC4-R blockade by coinjected HS014 (1 microg) not only prevented, but reversed the effect of alpha-MSH (1 microg) on Tc, thus resulting in augmented LPS-induced fever. In afebrile rats, alpha-MSH infusion caused a modest transient increase in Tc that was blocked by coinjected HS014, but was not accompanied by altered Tsk. Overall, the results support the hypothesis that the MC4R mediates the antipyretic effects of alpha-MSH. Paradoxically, in the presence of pharmacological MC4-R blockade during fever, exogenous alpha-MSH can exacerbate fever, probably by acting via other central MCR subtype(s). In normal animals, centrally injected alpha-MSH exerts a hyperthermic effect that is mediated by the MC4R, consistent with recent evidence that MC4R activation promotes energy expenditure in normal states through stimulation of thermogenesis.

The Effect of Central Injection of Angiotensin-Converting Enzyme Inhibitor and the Angiotensin Type 1 Receptor Antagonist on the Induction by Lipopolysaccharide of Fever and Brain Interleukin-1β Response in Rats

We recently reported an involvement of peripheral angiotensin II (ANG II) in the development of both the fever and the peripheral interleukin (IL)-1beta production induced in rats by a systemic injection of lipopolysaccharide (LPS). The present study was performed to investigate whether brain ANG II contributes to the fever and IL-1beta production in the rat brain induced by i.c.v. injection of LPS. LPS (0.2 and 2 microg i.c.v.) induced dose-related fevers and increases in the brain (hypothalamus, hippocampus, and cerebellum) concentrations of IL-1beta. These effects were significantly inhibited by i.c.v. administration of either an angiotensin-converting-enzyme (ACE) inhibitor or an angiotensin type 1 (AT(1)) receptor antagonist. By contrast, the ACE inhibitor had no effect on the IL-1beta (i.c.v.)-induced fever, whereas the AT(1) receptor antagonist enhanced (rather than reduced) it. The AT(1) receptor antagonist had no effect on the brain levels of prostaglandin E(2) in rats given an i.c.v. injection of IL-1beta. These results suggest that in rats, brain ANG II and AT(1) receptors are involved in the LPS-induced production of brain IL-1beta, thus contributing to the fever induced by the presence of LPS within the brain.

The organum vasculosum laminae terminalis in immune-to-brain febrigenic signaling: a reappraisal of lesion experiments

The organum vasculosum laminae terminalis (OVLT) has been proposed to serve as the interface for blood-to-brain febrigenic signaling, because ablation of this structure affects the febrile response. However, lesioning the OVLT causes many "side effects" not fully accounted for in the fever literature. By placing OVLT-lesioned rats on intensive rehydration therapy, we attempted to prevent these side effects and to evaluate the febrile response in their absence. After the OVLT of Sprague-Dawley rats was lesioned electrolytically, the rats were given access to 5% sucrose for 1 wk to stimulate drinking. Sucrose consumption and body mass were monitored. The animals were examined twice a day for signs of dehydration and treated with isotonic saline (50 ml/kg sc) when indicated. This protocol eliminated mortality but not several acute and chronic side effects stemming from the lesion. The acute effects included adipsia and gross (14% of body weight) emaciation; chronic effects included hypernatremia, hyperosmolality, a suppressed drinking response to hypertonic saline, and previously unrecognized marked (by approximately 2 degrees C) and long-lasting (>3 wk) hyperthermia. Because the hyperthermia was not accompanied by tail skin vasoconstriction, it likely reflected increased thermogenesis. After the rats recovered from the acute (but not chronic) side effects, their febrile response to IL-1beta (500 ng/kg iv) was tested. The sham-operated rats developed typical monophasic fevers ( approximately 0.5 degrees C), the lesioned rats did not. However, the absence of the febrile response in the OVLT-lesioned rats likely resulted from the untreatable side effects. For example, hyperthermia at the time of pyrogen injection was high enough (39-40 degrees C) to solely prevent fever from developing. Hence, the changed febrile responsiveness of OVLT-lesioned animals is given an alternative interpretation, unrelated to febrigenic signaling to the brain.

Activation of central melanocortin-4 receptor suppresses lipopolysaccharide-induced fever in rats

Activation of central melanocortin receptors (MCR) inhibits fever, but the identity of the MCR subtype(s) mediating this antipyretic effect is unknown. To determine whether selective central melanocortin receptor-4 (MC4R) activation produces antipyretic effects, the MC4R selective agonist MRLOB-0001 (CO-His-d-Phe-Arg-Trp-Dab-NH(2)) was administered intracerebroventricularly to rats treated with Escherichia coli lipopolysaccharide (LPS, 30 microg/kg ip). Treatment with MRLOB-0001 (150 ng icv) did not lower core body temperature (T(c)) in afebrile rats but did suppress LPS-induced increases in T(c) and associated decreases in tail skin temperature (T(sk)), an indicator of vasomotor thermoeffector function. In contrast, systemic treatment with MRLOB-0001 (150 ng iv) did not produce similar antipyretic effects. Coadministration of the selective MC4R antagonist HS014 (1 microg icv) blocked the antipyretic effects of MRLOB-0001. HS014 alone (1 microg icv) had no significant effect on LPS-induced increases in T(c) or decreases in T(sk) and in afebrile rats had no significant effects on T(c) or T(sk). We conclude that pharmacological activation of central MC4R suppresses febrile increases in T(c) and that inhibition of heat conservation pathways may contribute to this effect. These findings suggest that the central MC4R may mediate the long-recognized antipyretic effects of centrally administered melanocortins.

Endogenous interleukin-10 is required for the defervescence of fever evoked by local lipopolysaccharide-induced and Staphylococcus aureus-induced inflammation in rats

We tested the hypothesis that endogenous interleukin (IL)-10 limits the fever induced by a Gram-negative bacterial toxin (Escherichia coli lipopolysaccharide, LPS) and a Gram-positive bacterial toxin (Staphylococcus aureus), when these toxins are injected into a subcutaneous air pouch (I.PO.) in rats. Injection of LPS or S. aureus caused fevers that were reduced in amplitude and duration by simultaneous administration of rat recombinant IL-10. The inhibition of fever by IL-10 was accompanied by a significant reduction in the toxin-evoked increases in concentrations of immunoreactive IL-6 at the site of inflammation and of IL-6 and IL-1 receptor antagonist in the circulation. Conversely, neutralisation of endogenous IL-10 in the pouch increased the amplitude and dramatically increased the duration of toxin-evoked fever, and augmented toxin-induced increases in pouch tumour necrosis factor-alpha, IL-1beta, and especially IL-6. Our data support a crucial regulatory role for endogenous IL-10 in limiting the fever responses during both Gram-negative and Gram-positive infections.

The central melanocortin system and fever

Fever is a phylogenetically ancient response that is mounted upon exposure of the host to pathogens or inflammatory agents. Melanocortin agonists act centrally to inhibit fever by acting at receptors, including the melanocortin-4 receptor, which is prominently expressed in key hypothalamic thermoregulatory centers. Furthermore, endogenous melanocortins act centrally as physiological modulators of fever, recruited during the febrile response to restrain its intensity. Functionally, these actions lie at the interface between the anti-inflammatory effects of melanocortins, which involve suppression of the synthesis and actions of proinflammatory cytokines, and the central control of thermoregulation. Considering the extensive neuroanatomic and functional overlaps between central pathways and peripheral effectors involved in thermoregulation and energy balance, it is not surprising that melanocortins have been found to influence the metabolic economy profoundly in pathological as well as normal states. For example, despite suppressing endotoxin-induced fever, endogenous melanocortins appear to mediate the associated anorexia, a classic component of the "illness syndrome" accompanying acute infections, and promote a negative energy balance. The thermoregulatory actions of melanocortins are in several respects functionally opposed, and are remarkably dependent on physiological state, indicating that responsiveness to melanocortins is a physiologically modulated variable. Elucidating the anti-inflammatory and thermoregulatory roles of central melanocortin receptors during inflammatory states may lead to novel pharmacotherapeutic targets based on selective targeting of melanocortin receptor subtypes, for clinical benefit in human disease states involving neuroinflammatory components and metabolic wasting.

ANG II is involved in the LPS-induced production of proinflammatory cytokines in dehydrated rats

We have previously reported results that led us to speculate that ANG II is involved in the LPS-induced production of proinflammatory cytokines, especially under dehydrated conditions. To test this possibility, in this study we examined the effects of an angiotensin-converting enzyme (ACE) inhibitor and an antagonist of the type-1 ANG II receptor (AT(1) receptor) on the LPS-induced production of the proinflammatory cytokines IL-1 and IL-6 in dehydrated rats. A single intravenous injection of LPS induced a marked increase in the expression of IL-1beta mRNA in the liver, an effect that was significantly attenuated by pretreatment with the ACE inhibitor. Furthermore, the ACE inhibitor reduced the LPS-induced increase in the hepatic concentration of IL-1beta protein. When the AT(1)-receptor antagonist was given intravenously before the LPS, the increase in the hepatic concentration of IL-1beta was significantly reduced. Finally, the ACE inhibitor reduced the LPS-induced increase in the plasma concentration of IL-6. These results represent the first in vivo evidence that ANG II and its AT(1) receptor play important roles in the production of proinflammatory cytokines that is induced by LPS under dehydrated conditions.

Alpha-melanocyte stimulating hormone suppresses intracerebral tumor necrosis factor-alpha and interleukin-1beta gene expression following transient cerebral ischemia in mice

Following stroke, an intracerebral inflammatory response develops that may contribute to postischemic central nervous system injury. This study's objective was to determine whether the anti-inflammatory neuropeptide alpha-melanocyte stimulating hormone (MSH) can suppress postischemic activation of intracerebral tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) gene expression. Ipsilateral TNF-alpha levels were increased in cerebrocortical territory of the middle cerebral artery (MCA) following transient unilateral MCA occlusion (MCAO) and reperfusion in mice, and systemic alpha-MSH treatment (0.5 mg/kg i.p.) suppressed this increase. Systemic alpha-MSH treatment also inhibited the marked increases in cortical TNF-alpha and IL-1beta mRNA levels following MCAO, and reduced the intracerebral TNF-alpha protein levels seen after transient global ischemia. We conclude that alpha-MSH treatment suppresses intracerebral proinflammatory cytokine gene expression following transient cerebral ischemia, suggesting that systemically administered melanocortins may exert neuroprotective effects in cerebral ischemia.