Endogenous antipyretics

Modulation of the Acute Inflammatory Response Induced by the Escherichia coli Lipopolysaccharide through the Interaction of Pentoxifylline and Florfenicol in a Rabbit Model

BACKGROUND

Experimental reports have demonstrated that florfenicol (FFC) exerts potent anti-inflammatory effects, improving survival in a murine endotoxemia model. Considering the anti-inflammatory and immunomodulatory properties of pentoxifylline (PTX) as an adjuvant to enhance the efficacy of antibiotics, the anti-inflammatory effects of the interaction FFC/PTX over the E. coli Lipopolysaccharide (LPS)-induced acute inflammatory response was evaluated in rabbits.

METHODS

Twenty-five clinically healthy New Zealand rabbits (3.8 ± 0.2 kg body weight: bw), were distributed into five experimental groups. Group 1 (control): treated with 1 mL/4 kg bw of 0.9% saline solution (SS) intravenously (IV). Group 2 (LPS): treated with an IV dose of 5 µg/kg of LPS. Group 3 (pentoxifylline (PTX) + LPS): treated with an oral dose of 30 mg/kg PTX, followed by an IV dose of 5 µg/kg of LPS 45 min after PTX. Group 4 (Florfenicol (FFC) + LPS): treated with an IM dose of 20 mg/kg of FFC, followed by an IV dose of 5 µg/kg of LPS 45 min after FFC administration. Group 5 (PTX + FFC + LPS): treated with an oral dose of 30 mg/kg of PTX, followed by an IM dose of 20 mg/kg of FFC, and, 45 min after an IV dose of 5 µg/kg of LPS was administered. The anti-inflammatory response was evaluated through changes in plasma levels of interleukins (TNF-α, IL-1β and IL-6), C-reactive protein (CRP), and body temperature.

RESULTS

It has been shown that each drug produced a partial inhibition over the LPS-induced increase in TNF-α, IL-1β, and CRP. When both drugs were co-administered, a synergistic inhibitory effect on the IL-1β and CRP plasma concentrations was observed, associated with a synergic antipyretic effect. However, the co-administration of PTX/FFC failed to modify the LPS-induced increase in the TNF-α plasma concentrations.

CONCLUSIONS

We concluded that the combination of FFC and PTX in our LPS sepsis models demonstrates immunomodulatory effects. An apparent synergistic effect was observed for the IL-1β inhibition, which peaks at three hours and then decreases. At the same time, each drug alone was superior in reducing TNF-α levels, while the combination was inferior. However, the peak of TNF-α in this sepsis model was at 12 h. Therefore, in rabbits plasma IL-1β and TNF-α could be regulated independently, thus, further research is needed to explore the effects of this combination over a more prolonged period.

Impact of an Educational Program on Improving Nurses’ Management of Fever: An Experimental Study

Background: Despite a public information campaign “To Break the Myth of Fever”, nurses continued to overtreat fever. This study hypothesized that the campaign lacked the detailed rationale essential to alter nurses’ attitudes and behaviors. Aim: To evaluate the effect of the educational program on nurses’ knowledge, attitudes, and behaviors related to fever management. Design: A randomized experimental design using a time series analysis. Methods: A random sample of 58 medical/surgical nurses was evenly divided into an intervention and a control group. The intervention group received an educational program on fever and fever management. Both groups completed a pretest and four posttests using investigator-developed instruments: a questionnaire on knowledge and attitudes about fever management and a fever treatment checklist to audit charts. Results: The intervention group had markedly higher knowledge scores and reduced use of ice pillows at all four posttests, as well as lower use of antipyretics overall, except for the first posttest, despite no sustained change in attitude. Conclusions: An educational program for fever management can effectively improve clinical nurses’ knowledge and attitudes about fever management.

Genome-wide association study of febrile seizures implicates fever response and neuronal excitability genes

Febrile seizures represent the most common type of pathological brain activity in young children and are influenced by genetic, environmental and developmental factors. In a minority of cases, febrile seizures precede later development of epilepsy.

We conducted a genome-wide association study of febrile seizures in 7635 cases and 83 966 controls identifying and replicating seven new loci, all with P < 5 × 10⁻¹⁰.

Variants at two loci were functionally related to altered expression of the fever response genes PTGER3 and IL10, and four other loci harboured genes (BSN, ERC2, GABRG2, HERC1) influencing neuronal excitability by regulating neurotransmitter release and binding, vesicular transport or membrane trafficking at the synapse. Four previously reported loci (SCN1A, SCN2A, ANO3 and 12q21.33) were all confirmed. Collectively, the seven novel and four previously reported loci explained 2.8% of the variance in liability to febrile seizures, and the single nucleotide polymorphism heritability based on all common autosomal single nucleotide polymorphisms was 10.8%. GABRG2, SCN1A and SCN2A are well-established epilepsy genes and, overall, we found positive genetic correlations with epilepsies (r_g = 0.39, P = 1.68 × 10⁻⁴). Further, we found that higher polygenic risk scores for febrile seizures were associated with epilepsy and with history of hospital admission for febrile seizures. Finally, we found that polygenic risk of febrile seizures was lower in febrile seizure patients with neuropsychiatric disease compared to febrile seizure patients in a general population sample.

In conclusion, this largest genetic investigation of febrile seizures to date implicates central fever response genes as well as genes affecting neuronal excitability, including several known epilepsy genes. Further functional and genetic studies based on these findings will provide important insights into the complex pathophysiological processes of seizures with and without fever.

Antibacterial, anti-inflammatory and antioxidant activities of Mahanintangtong and its constituent herbs, a formula used in Thai traditional medicine for treating pharyngitis

Background

Mahanintangtong is listed in the Thailand’s National List of Essential Medicines (NLEM). It is used to treat non-specific fevers and illnesses such as pharyngitis and chickenpox. In this study, we investigated the biological activities of the different medicinal plants used in the Mahanintangtong formula.

Methods

The plant materials were extracted by maceration and decoction. Antimicrobial activity, assessed by disc diffusion method, the minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were compared with commercially available standard antibiotics. To elucidate the anti-inflammatory mechanisms, inhibition of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) production was tested by Griess and ELISA techniques. Antioxidant activity was measured by ABTS and DPPH scavenging assays.

Results

The extracts with the best antimicrobial activities were carbonized Tectona grandis showing against Streptococcus pyogenes, Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The ethanol extract of Dracaena loureiroi wood exhibited the highest NO and IL-6 inhibitory activity with IC₅₀ values of 9.42 ± 1.81 and 12.02 ± 0.30 μg/mL, respectively. The ethanol extract of Pogostemon cablin had the highest TNF-α inhibitory with IC₅₀ values of 10.68 ± 0.02 μg/mL. In anti-free radical testing, the ethanol extract of D. loureiroi displayed high antioxidant activity by both ABTS and DPPH assays.

Conclusion

The ethanol extracts from carbonized T. grandis and Mahanintangtong showed good antimicrobial activity, especially against S. pyogenes, and good anti-inflammatory activity. These findings are relevant to the pathogenesis of pharyngitis and justify additional studies to see if Mahanintangtong could have clinical utility.

A benzimidazole inhibitor attenuates sterile inflammation induced in a model of systemic autoinflammation in female mice

Sterile stimuli can trigger inflammatory responses, and in some cases can lead to a variety of acute or chronic diseases. In this study, we hypothesize that a benzimidazole inhibitor may be used as a therapeutic in the treatment of sterile inflammation. In vitro, this inhibitor blocks TLR signalling and inflammatory responses. The benzimidazole inhibitor does not prevent mouse macrophage activation after stimulation with 2,6,10,14-tetramethylpentadecane (TMPD, also known as pristane), a hydrocarbon oil that mimics features of sterile inflammation when injected in vivo. However, C57BL/6J female mice treated with the benzimidazole inhibitor exhibited a significant reduction of pristane-dependent induction of splenocyte number and weight. Conversely, no significant difference was observed in males. Using mass spectrometry, we found that the urine of pristane-injected mice contained increased levels of putative markers for several inflammatory diseases, which were reduced by the benzimidazole inhibitor. To study the mechanism, we showed that pristane-injected mice had increased cell free DNA in serum, which was not impacted by inhibitor treatment. However, chemokine release (e.g. MCP-1, RANTES and TARC) was significantly reduced in inhibitor-treated mice. Thus, the benzimidazole inhibitor might be used as a new drug to block the recruitment of immune cells during sterile inflammatory diseases in humans.

Viscosine as a Potent and Safe Antipyretic Agent Evaluated by Yeast-Induced Pyrexia Model and Molecular Docking Studies

The antipyretic potential of viscosine, a natural product isolated from the medicinal plant Dodonaea viscosa, was investigated using yeast-induced pyrexia rat model, and its structure-activity relationship was investigated through molecular docking analyses with the target enzymes cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and microsomal prostaglandin E synthase-1 (mPGES-1). The in vivo antipyretic experiments showed a progressive dose-dependent reduction in body temperatures of the hyperthermic test animals when injected with viscosine. Comparison of docking analyses with target enzymes showed strongest bonding interactions (binding energy -17.34 kcal/mol) of viscosine with the active-site pocket of mPGES-1. These findings suggest that viscosine shows antipyretic properties by reducing the concentration of prostaglandin E₂ in brain through its mPGES-1 inhibitory action and make it a potential lead compound for developing effective and safer antipyretic drugs for treating fever and related pathological conditions.

Evaluation of anti-inflammatory potential of the leaves of Wendlandia heynei (Schult.) Santapau & Merchant in Sprague Dawley rat

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of W. heynei (family: Rubiaceae) are used by the folklore in swelling, wounds and body aches. In this study anti-inflammatory potential of W. heynei leaves has been evaluated during in vitro studies and in rat.

METHODS

Methanol extract of the leaves of W. heynei (WHLM) and its fractions; n-hexane (WHLH), chloroform (WHLC), ethyl acetate (WHLE), n-butanol (WHLB) and residual soluble aqueous (WHLA) were screened for phytochemical analysis and several active constituents (alkaloids, flavonoids, saponins, tannins, terpenoids, β-carotene and lycopene) were also quantified. Heat induced albumin denaturation assay and in vitro cell cultures was carried out for in vitro anti-inflammatory activity, while various in vivo assays like TPA induced ear edema, croton oil induced anus edema, formalin and carrageenan-induced hind paw edema was investigated in Sprague-Dawley rats. Alterations on levels of tumor necrosis factor (TNF-α), Interleukin-1β (IL-1β), IL-6 and prostaglandins (PGE₂) induced with WHLE was studied in serum after carrageenan induced paw edema in rat. Meanwhile, the dose dependent WHLE inhibition of NFκB pathway via regulation of the phosphorylation of IKKs, IκBα, and p65 subunit was studied in LPS-induced rat peritoneal macrophages. On account of marked anti-inflammatory activity of WHLE its bioactive components were analyzed by HPLC-DAD analysis.

RESULTS

The phytochemical analysis yielded alkaloids, saponins, tannins, coumarins, glycosides, quinones and vitamin C in WHLM and in all fractions. Fraction (WHLE) was enriched with alkaloids (20.20 ± 2.5%), flavonoids (25.26 ± 2.11%) and tannins (307.2 ± 2.03 mg of GAE/g of extract), while terpenoids (21.60 ± 1.65%) were the major constituents of WHLH. Ethyl acetate fraction convincingly protected heat induced albumin denaturation. WHLE exhibited highest edema inhibition in models of TPA-induced ear edema (74.51 ± 2.05) and croton oil-induced anal edema (75.38 ± 2.83). The pretreatment with WHLE significantly (p < 0.05) reduced the paw edema with formalin (78.99 ± 2.26%) assessed after 6 h and in carrageenan (75.71 ± 4.46%) was detected after 4 h. Level of anti-inflammatory markers; IL-1β, IL-6, TNF-α and PGE₂ in carrageenan induced paw edema in serum of rat was significantly (p < 0.001) decreased with WHLE pretreatment to rat. WHLE significantly inhibited the NFκB by reducing the phosphorylation of IKKs, IκBα, and p65 subunit in LPS-induced inflammation in rat peritoneal macrophages. HPLC-DAD analysis of WHLE indicated the presence of rutin, gallic acid, catechin, caffeic acid and myricetin.

CONCLUSIONS

It is concluded that WHLM fractions have marked anti-inflammatory activity and this study endorsed the folklore use of W. heynei leaves for swelling related disorders.

Reverse Engineering the Febrile System

Fever, the elevation of core body temperature by behavioral or physiological means, is one of the most salient aspects of human sickness, yet there is debate regarding its functional role. In this paper, we demonstrate that the febrile system is an evolved adaptation shaped by natural selection to coordinate the immune system to fight pathogens. First, we show that previous arguments in favor of fever being an adaptation are epistemologically inadequate, and we describe how an adaptationist strategy addresses this issue more effectively. Second, we argue that the mechanisms producing fever provide clear indications of adaptation. Third, we demonstrate that there are many beneficial immune system responses activated during fever and that these responses are not mere byproducts of heat on chemical reactions. Rather, we show that natural selection appears to have modified several immune system effects to be coordinated by fever. Fourth, we argue that there are some adaptations that coordinate the febrile system with other important fitness components, particularly growth and reproduction. Finally, we discuss evidence that the febrile system may also have evolved an antitumor function, providing suggestions for future research into this area. This research informs the debate on the functional value of fever and antipyretic use.

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.

The Molecular Mechanism and Neuroprotective Effect of Dihydrocapsaicin-Induced Mild Hypothermia After Cardiopulmonary Resuscitation in Rats

To investigate the molecular mechanism of dihydrocapsaicin (DHC)-induced mild hypothermia in rats, and to compare its protective effect on the central nervous system with that of a conventional method of inducing hypothermia, 24 healthy male Sprague Dawley rats were randomly divided into four groups based on the following conditions: control group, cardiopulmonary resuscitation (CPR) group, body surface cooling group, and DHC group. Tracheal clipping was used to mimic asphyxia arrest. Rats were assessed for their neurological deficit scores. After sacrifice, immunohistochemical staining was used to examine caspase-3 expression in the cerebral cortex and TRPV1 (transient receptor potential vanilloid subfamily, member 1) expression in the hypothalamus. Terminal TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining was used to evaluate cell apoptosis in the cerebral cortex. Furthermore, intracellular Ca²⁺ concentration in the hypothalamus and arginine vasopressin (AVP) concentration in ventral septal tissues were also detected in these four groups. Results of our study showed that neurological deficit scores in the DHC group were significantly higher than those in the CPR and body surface cooling groups (p < 0.05). Caspase-3 expression in the cerebral cortex of control group rats was significantly lower than that in other three groups (p < 0.05). Hypothalamic TRPV1 expression, hypothalamic intracellular Ca²⁺ concentration, and AVP concentration in the ventral septum in the DHC group were significantly higher than that in the other three groups (p < 0.05). Within these three groups, there were significantly fewer apoptotic cells in the DHC and body surface cooling group rats than in the CPR group rats (p < 0.05). DHC has the neuroprotective effect. DHC induced mild hypothermia and reduces apoptosis through a mechanism whereby DHC activates TRPV1 on hypothalamic cells to cause a large Ca²⁺ influx, which alters corresponding physiological functions and causes the release of AVP to induce hypothermia.

Fever and sickness behavior: Friend or foe?

Fever has been recognized as an important symptom of disease since ancient times. For many years, fever was treated as a putative life-threatening phenomenon. More recently, it has been recognized as an important part of the body's defense mechanisms; indeed at times it has even been used as a therapeutic agent. The knowledge of the functional role of the central nervous system in the genesis of fever has greatly improved over the last decade. It is clear that the febrile process, which develops in the sick individual, is just one of many brain-controlled sickness symptoms. Not only will the sick individual appear "feverish" but they may also display a range of behavioral changes, such as anorexia, fatigue, loss of interest in usual daily activities, social withdrawal, listlessness or malaise, hyperalgesia, sleep disturbances and cognitive dysfunction, collectively termed "sickness behavior". In this review we consider the issue of whether fever and sickness behaviors are friend or foe during: a critical illness, the common cold or influenza, in pregnancy and in the newborn. Deciding whether these sickness responses are beneficial or harmful will very much shape our approach to the use of antipyretics during illness.

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.

Pharmacotherapy of fever control among hospitalized adult patients

INTRODUCTION

Fever is common and associated with increased mortality among hospitalized adults. This article will review the pharmacotherapy of commonly prescribed antipyretic drugs including the rationale for and against temperature control in febrile adults, as well as the evidence associated with fever control in specific patient populations.

AREAS COVERED

Though fever is common, the molecular basis of pyrexia, and the interaction of these pathways with commonly prescribed antipyretic drugs are not fully understood. Furthermore, while experimental and clinical studies clearly demonstrate that pyrexia is harmful in select patients, available clinical trial data are unable to suggest an evidence-based approach to the treatment of fever. Interestingly, this also applies to patients with an acute neurologic injury wherein the treatment of fever with antipyretic therapy has become a common management strategy.

EXPERT OPINION

Few adequately powered clinical trials have investigated temperature control strategies in febrile patients. Therefore, it is not possible to define an evidence-based approach to the control of fever in hospitalized adults. Further clinical and translational research is required to identify the patients most likely to benefit from a strategy of fever control versus permissive hyperthermia, and to determine the antipyretic therapies associated with the greatest improvement in outcome.

Glucocorticoid receptor dimerization is required for proper recovery of LPS-induced inflammation, sickness behavior and metabolism in mice

Endogenous glucocorticoids are essential for mobilizing energy resources, restraining inflammatory responses and coordinating behavior to an immune challenge. Impaired glucocorticoid receptor (GR) function has been associated with impaired metabolic processes, enhanced inflammation and exaggerated sickness and depressive-like behaviors. To discern the molecular mechanisms underlying GR regulation of physiologic and behavioral responses to a systemic immune challenge, GR(dim) mice, in which absent GR dimerization leads to impaired GR-DNA-binding-dependent mechanisms but intact GR protein-protein interactions, were administered low-dose lipopolysaccharide (LPS). GR(dim)-LPS mice exhibited elevated and prolonged levels of plasma corticosterone (CORT), interleukin (IL)-6 and IL-10 (but not plasma tumor necrosis factor-α (TNFα)), enhanced early expression of brain TNFα, IL-1β and IL-6 mRNA levels, and impaired later central TNFα mRNA expression. Exaggerated sickness behavior (lethargy, piloerection, ptosis) in the GR(dim)-LPS mice was associated with increased early brain proinflammatory cytokine expression and late plasma CORT levels, but decreased late brain TNFα expression. GR(dim)-LPS mice also exhibited sustained locomotor impairment in the open field, body weight loss and metabolic alterations measured by indirect calorimetry, as well as impaired thermoregulation. Taken together, these data indicate that GR dimerization-dependent DNA-binding mechanisms differentially regulate systemic and central cytokine expression in a cytokine- and time-specific manner, and are essential for the proper regulation and recovery of multiple physiologic responses to low-dose endotoxin. Moreover, these results support the concept that GR protein-protein interactions are not sufficient for glucocorticoids to exert their full anti-inflammatory effects and suggest that glucocorticoid responses limited to GR monomer-mediated transcriptional effects could predispose individuals to prolonged behavioral and metabolic sequelae of an enhanced inflammatory state.

Effects of dietary fish meal and soybean meal on the ovine innate and acquired immune response during pregnancy and lactation

In recent years, livestock producers have been supplementing animal diets with fish meal (FM) to produce value-added products for health conscious consumers. As components of FM have unique neuroendocrine-immunomodulatory properties, we hypothesize that livestock producers may be influencing the overall health of their animals by supplementing diets with FM. In this study, 40 pregnant ewes were supplemented with rumen protected (RP) soybean meal (SBM: control diet) or RP FM, commencing gestation day 100 (gd100), in order to evaluate the impact of FM supplementation on the innate and acquired immune response and neuroendocrine response of sheep during pregnancy and lactation. On gd135, half the ewes from each diet (n = 10 FM, n = 10 SBM) were challenged iv with lipopolysaccharide (LPS) to simulate a systemic bacterial infection and the febrile, respiratory and neuroendocrine responses were monitored over time; the other half (n = 10 FM, n = 10 SBM) of the ewes received a saline injection as control. On lactation day 20 (ld20), all ewes (n = 20 FM, n = 20 SBM) were sensitized with hen egg white lysozyme (HEWL) and the serum haptoglobin (Hp) response was measured over time. The cutaneous hypersensitivity response (CHR) to HEWL challenge was measured on ld30 (n = 20 FM, n = 20 SBM), and blood samples were collected over time to measure the primary and secondary immunoglobulin G (IgG) response to HEWL. There was an attenuated trend in the LPS-induced febrile response by the FM treatment when compared with the SBM treatment (P = 0.06), as was also true for the respiratory response (P = 0.07), but significant differences in neuroendocrine function (serum cortisol and plasma ACTH) were not observed between treatments. Basal Hp levels were significantly lower in the FM supplemented ewes when compared with the SBM supplemented ewes (P < 0.01), and the Hp response to HEWL sensitization differed significantly over time between treatments (P < 0.01). The CHR to HEWL was also significantly attenuated in the FM treatment compared with the SBM (P < 0.01); however, treatment differences in the primary and secondary IgG responses to HEWL were not observed. These results indicate that FM supplementation differentially affects the innate and acquired immune responses in pregnant and lactating sheep compared with a typical SBM diet of commercial flocks. The long-term implications of this immunomodulation warrant further investigation.

Molecular pathways linking metabolic inflammation and thermogenesis

Obesity is caused by chronic positive energy balance because of higher energy intake relative to energy expenditure. Thermogenesis, the capacity of an organism to produce heat, is an important component of energy expenditure. Thus targeting the molecular mechanisms controlling thermogenesis could be an effective strategy for the prevention or treatment of obesity. Thermogenesis is modulated by three major factors: environmental temperature, nutrient quantity and quality, and by systemic inflammation. Obesity is now recognized to be a state of chronic low-grade systemic inflammation, which has been proposed to play a major role in the pathogenesis of obesity and obesity-associated diseases. This review discussed the molecular pathways that are recruited during metabolic inflammation and that are also implicated in the control of thermogenesis and energy balance. It emerges that the complex signalling network recruited during metabolic inflammation exerts a balanced action on the modulation of thermogenesis and energy balance, with some pathways promoting weight gain whereas other pathways have opposite actions. It is thus concluded that immunomodulation of metabolic inflammation, rather than an anti-inflammatory intervention aiming at its suppression, may be a more promising strategy to increase thermogenesis for the treatment or prevention of obesity and its associated diseases.

Antipyretic activity of Guduchi Ghrita formulations in albino rats

The present pharmacological investigation was undertaken to study the anti-pyretic activity of Guduchi ghrita formulations in albino rats against yeast induced pyrexia. Seven groups of six animals were used for the experiment. The yeast induced pyrexia method was standardized first by injecting 12.5% yeast suspension (s.c) followed by recording the rectal temperature at regular intervals. Then the evaluation of anti-pyretic activity of Guduchi ghrita formulations was carried out by using this standard procedure. Both the Guduchi ghrita samples including vehicle significantly attenuated the raise in temperature after three hours of yeast injection. After 6 and 9 hours of yeast injection also both the Guduchi ghrita samples attenuated the raise in temperature in a highly significant manner in comparison to both yeast control and vehicle control groups. The data generated during study shows that both the Guduchi ghrita formulations having significant anti-pyretic activity.

Fever induction by systemic stimulation with macrophage-activating lipopeptide-2 depends upon TLR2 but not CD36

This study was designed to test the responses of TLR2-knockout mice (TLR2-KO) and wild- type mice (C57/BL-6), and of CD36 deficient spontaneously hypertensive rats (SHR) and their genetic controls [Wistar Kyoto (WKY) rats] to systemic stimulations with the TLR2/6 agonist MALP-2 and the TLR4 agonist LPS. Fever and formation of TNF-α and IL-6 induced by intraperitoneal injections of MALP-2 (1000 µg/kg) were completely blunted in TLR2-KO, while LPS (100 µg/kg)-induced responses were not abolished in these animals. In SHR lacking CD36, a reduction of fever was observed in response to MALP-2 (100 µg/kg), but LPS-fever was even more attenuated in SHR when compared with WKY controls. Concentrations of circulating IL-6 tended to be lower in SHR after stimulation with both pyrogens. However, the IL-6-mediated activation of the transcription factor STAT3 in the brain was identical in both strains, indicating that the brain-controlled inflammatory response to MALP-2 (and LPS) is not impaired in the absence of CD36. In addition, stimulation of peritoneal macrophages with LPS and MALP-2 (10 µg/ml) caused the appearance of similar concentrations of bioactive cytokines in the supernatants from cells of both rat strains. These results demonstrate that TLR2 is essential for the manifestation of MALP-2, but not LPS-induced inflammatory responses. A moderate participation of CD36 in MALP-2-induced sickness- and cytokine-responses can not be ruled out but is unlikely as LPS-induced inflammatory responses were also attenuated in SHR.

Endotoxin exposure during late pregnancy alters ovine offspring febrile and hypothalamic-pituitary-adrenal axis responsiveness later in life

A growing number of studies indicate that maternal infection during pregnancy is associated with adverse fetal development and neonatal health. In this study, late gestating sheep (day 135) were challenged systemically with saline (0.9%) or Escherichia coli lipopolysaccharide endotoxin (400 ng/kg x 3 consecutive days, or 1.2 microg/kg x 1 day) in order to assess the impact of maternal endotoxemia on the developing fetal neuroendocrine-immune system. During adulthood, cortisol secretion and febrile responses of female offspring and the cortisol response of the male offspring to endotoxin (400 ng/kg), as well as the female cortisol response to adrenocorticotropic hormone (ACTH) challenge, were measured to assess neuroendocrine-immune function. These studies revealed that maternal endotoxin treatment during late gestation altered the female febrile and male and female cortisol response to endotoxin exposure later in life; however, the response was dependent on the endotoxin treatment regime that the pregnant sheep received. The follow-up ACTH challenge suggests that programing of the adrenal gland may be altered in the female fetus during maternal endotoxemia. The long-term health implications of these changes warrant further investigation.

High fever following postpartum administration of sublingual misoprostol

Objective

To explore what triggers an elevated body temperature of ≥40.0°C in some women given misoprostol, a prostaglandin E1 analogue, for postpartum haemorrhage (PPH).

Design

Post hoc analysis.

Setting

One tertiary-level hospital in Quito, Ecuador.

Population

A cohort of 58 women with a fever of above 40°C following treatment with sublingual misoprostol (800 micrograms) for PPH.

Methods

Side effects were documented for 163 Ecuadorian women given sublingual misoprostol to treat their PPH. Women’s body temperatures were measured, and if they had a fever of ≥40.0°C, measurements were taken hourly until the fever subsided. Temperature trends were analysed, and the possible physiological mechanisms by which postpartum misoprostol produces a high fever were explored.

Main outcome measures

The onset, duration, peak temperatures, and treatments administered for cases with a high fever.

Results

Fifty-eight of 163 women (35.6%) treated with misoprostol experienced a fever of ≥40.0°C. High fevers followed a predictable pattern, often preceded by moderate/severe shivering within 20 minutes of treatment. Body temperatures peaked 1–2 hours post-treatment, and gradually declined over 3 hours. Fevers were transient and did not lead to any hospitalisation. Baseline characteristics were comparable among women who did and did not develop a high fever, except for known previous PPH and time to placental expulsion.

Conclusions

An unexpectedly high rate of elevated body temperature of ≥40.0°C was documented in Ecuador following sublingually administered misoprostol. It is unclear why temperatures ≥40.0°C occurred with a greater frequency in Ecuador than in other study populations using similar treatment regimens for PPH. Pharmacogenetic studies may shed further light on variations in individuals’ responses to misoprostol.

Characterization and pharmacological evaluation of febrile response on zymosan-induced arthritis in rats

The present study investigated the febrile response in zymosan-induced arthritis, as well as the increase in PGE2concentration in the cerebrospinal fluid (CSF), along with the effects of antipyretic drugs on these responses in rats. Zymosan intra-articularly injected at the dose of 0.5 mg did not affect the body core temperature (Tc) compared with saline (control), whereas at doses of 1 and 2 mg, zymosan promoted a flattened increase in Tc and declined thereafter. The dose of 4 mg of zymosan was selected for further experiments because it elicited a marked and long-lasting Tc elevation starting at 3 1/2 h, peaking at 5 1/2 h, and remaining until 10 h. This temperature increase was preceded by a decrease in the tail skin temperature, as well as hyperalgesia and edema in the knee joint. No febrile response was observed in the following days. In addition, zymosan-induced fever was not modified by the sciatic nerve excision. Zymosan increased PGE2concentration in the CSF but not in the plasma. Oral pretreatment with ibuprofen (5–20 mg/kg), celecoxib (1–10 mg/kg), dipyrone (60–240 mg/kg), and paracetamol (100–200 mg/kg) or subcutaneous injection of dexamethasone (0.25–1.0 mg/kg) dose-dependently reduced or prevented the fever during the zymosan-induced arthritis. Celecoxib (5 mg/kg), paracetamol (150 mg/kg), and dipyrone (120 mg/kg) decreased CSF PGE2concentration and fever during zymosan-induced arthritis, suggesting the involvement of PGE2in this response.

Release of ATP in the central nervous system during systemic inflammation: real-time measurement in the hypothalamus of conscious rabbits

Receptors for extracellular ATP (both ionotropic and metabotropic) are widely expressed in the CNS both in neurones and glia. ATP can modulate neuronal activity in many parts of the brain and contributes to the central nervous control of several physiological functions. Here we show that during the systemic inflammatory response the extracellular concentrations of ATP increase in the anterior hypothalamus and this has a profound effect on the development of the thermoregulatory febrile response. In conscious rabbits we measured ATP release in real time with novel amperometric biosensors and monitored a marked increase in the concentration of ATP (4.0 ± 0.7 μm) in the anterior hypothalamus in response to intravenous injection of bacterial endotoxin – lipopolysaccharide (LPS). No ATP release was observed in the posterior hypothalamus. The release of ATP coincided with the development of the initial phase of the febrile response, starting 18 ± 2 min and reaching its peak 45 ± 2 min after LPS injection. Application of the ATP receptor antagonists pyridoxal-5′-phosphate-6-azophenyl-2′,4′-disulphonic acid, Brilliant Blue G or periodate oxidized ATP dialdehyde to the site of ATP release in the anterior hypothalamus markedly augmented and prolonged the febrile response. These data indicate that during the development of the systemic inflammation, ATP is released in the anterior hypothalamus to limit the magnitude and duration of fever. This release may also have a profound effect on the hypothalamic control of other physiological functions in which ATP and related purines have been implicated to play modulatory roles, such as food intake, hormone secretion, cardiovascular activity and sleep.

Attenuated fever in rats during late pregnancy is linked to suppressed interleukin-6 production after localized inflammation with turpentine

An attenuated fever response to pathogens during late pregnancy is a phenomenon that has been described in several mammalian species, and although mechanisms are not completely understood, decreased prostaglandin E2 (PGE2) synthesis has been implicated. Upstream of PGE2, there is evidence to suggest that anti-inflammatory cytokines such as interleukin-1 receptor antagonist (IL-1ra) could play a significant role. In the present study we addressed the role of pro-inflammatory cytokines during late pregnancy, specifically interleukin-6 (IL-6), an important circulating mediator in fever. Turpentine oil (TURP), a very potent pyrogen and activator of IL-6, was injected into the hind-limb muscle of rats at the 18th day of pregnancy (GD 18) or in non-pregnant (NP) age-matched female controls. As expected, TURP injection induced a highly significant fever in the NP animals, which peaked 11 h post-injection and lasted for over 24 h. This was accompanied by a significant rise in circulating IL-6 levels, which correlated with changes in PGE2 synthesizing enzymes expression in the hypothalamus. In complete contrast, TURP-induced fever was totally absent in GD 18 animals whose body temperature did not deviate from basal values. The lack of response was additionally reflected by the absence of change in IL-6 concentration and by the significant attenuation of PGE2 synthesizing enzymes expression, which correlated with the suppressed expression of SOCS3, a hypothalamic marker of IL-6 activity. Contrary to the changes in circulating IL-6 levels at GD 18, IL-1ra was induced to levels comparable to those of NP females, suggesting that the influence of this anti-inflammatory cytokine on the fever response to TURP is at best minimal. These data further confirm the importance of IL-6 in fever generation and provide evidence that it may be a key component of the attenuated fever response in late pregnancy.