Central mediators involved in the febrile response: effects of antipyretic drugs

Increased LPS-induced fever and sickness behavior in adult male and female rats perinatally exposed to morphine

As a result of the current opioid crisis, the rate of children born exposed to opioids has skyrocketed. Later in life, these children have an increased risk for hospitalization and infection, raising concerns about potential immunocompromise, as is common with chronic opioid use. Opioids can act directly on immune cells or indirectly via the central nervous system to decrease immune system activity, leading to increased susceptibility, morbidity, and mortality to infection. However, it is currently unknown how perinatal opioid exposure (POE) alters immune function. Using a clinically relevant and translatable model of POE, we have investigated how baseline immune function and the reaction to an immune stimulator, lipopolysaccharide, is influenced by in utero opioid exposure in adult male and female rats. We report here that POE potentiates the febrile and neuroinflammatory response to lipopolysaccharide, likely due to suppressed immune function at baseline. This suggests that POE increases susceptibility to infection by manipulating immune system development, consistent with the clinical literature. Investigation of the mechanisms whereby POE increases susceptibility to pathogens is critical for the development of potential interventions for immunosuppressed children exposed to opioids in utero.

NK1 receptor mediates cerebral cellular and extracellular morphological changes during the LPS-induced febrile response

Fever elicited by bacterial lypopolyssacharide (LPS) is mediated by pro-inflammatory cytokines, which activate central mediators and regulate the hypothalamic temperature setpoint. This response is often accompanied by morphological changes involving the extracellular matrix, neurons and glial cells, with significant health impacts. The NK1 receptor is involved in the febrile response induced by LPS but its effects over the extracellular matrix in the context of neuroinflammation remain unknown. The present work aims to clarify the extracellular changes associated with NK1 signaling in LPS-induced fever. Male Wistar rats were exposed to LPS intraperitoneally. Experimental groups were pre-treated intracerebroventricularly with the NK1 selective inhibitor SR140333B or saline. Histological changes involving the brain extracellular matrix were evaluated using hematoxylin and eosin, Mason's trichrome, picrosirius, alcian blue, periodic acid Schiff's stains. The expression of matrix metalloproteinase 9 (MMP9) was studied using confocal microscopy. Fever was accompanied by edema, perivascular lymphoplamacytic and neutrophylic infiltration, spongiosis and MMP9 overexpression. SR140333B significantly reduced LPS-induced fever (p < 0.0001), MMP9 overexpression (p < 0.01) and associated histological changes. These results contribute to characterize cerebral extracellular matrix changes associated with LPS-induced fever. Overall, the present work supports a role for NK1 receptor in these neuroinflammatory changes, involving MMP9 overexpression, edema and leukocytic infiltration.

Sexual dimorphism of hypothalamic serotonin release during systemic inflammation: Role of endothelin-1

The hypothalamus receives serotonergic projections from the raphe nucleus in a sex-specific manner. During systemic inflammation, hypothalamic levels of serotonin (5-hydroxytryptamine [5-HT]) decrease in male rats. The present study evaluated the involvement of endothelin-1 (ET-1) in the febrile response, hypolocomotion, and changes in hypothalamic 5-HT levels during systemic inflammation in male and female rats. An intraperitoneal injection of lipopolysaccharide (LPS) induced a febrile response and hypolocomotion in both male and female rats. However, although LPS reduced hypothalamic levels of 5-HT and its metabolite 5-hydroxyindol acetic acid (5-HIAA) in male rats, it increased these levels in female rats. An intracerebroventricular injection of the endothelin-B receptor antagonist BQ788 significantly reduced LPS-induced fever and hypolocomotion and changes in hypothalamic 5-HT and 5-HIAA levels in both male and female rats. The i.c.v. administration of ET-1 induced a significant fever and hypolocomotion, but reduced the hypothalamic levels of 5-HT and 5-HIAA in both males and females. These results suggest an important sexual dimorphism during systemic inflammation regarding the release of 5-HT in the hypothalamus. Moreover, ET-1 arises as an important mediator involved in the changes in hypothalamic 5-HT levels in both male and female rats.

Pharmacological evaluation of anti-inflammatory, antipyretic, analgesic, and antioxidant activities of Castanopsis costata leaf fractions (water, ethyl acetate, and n-hexane fractions): the potential medicinal plants from North Sumatra, Indonesia

Background and purpose

Inflammation, fever, and pain can be associated with several diseases, and the synthetic drugs used in the treatment of these conditions often have severe side effects. As a result, there is a need for effective, economical, and safe alternative drugs, such as those derived from medicinal plants. Therefore, this study aimed to evaluate the anti-inflammatory, antipyretic, analgesic, and antioxidant activities of Castanopsis costata leaf fractions (CcLF), as well as its acute toxicity.

Experimental approach

For anti-inflammatory, antipyretic, and analgesic tests, rats were given CcLF (WFCC, EAFcC, and n-HFCC) at 50 and 100 mg/kg, diclofenac sodium (10 mg/kg), paracetamol (150 mg/kg), aspirin (100 mg/kg), and tramadol (20 mg/kg). For the antioxidant activity test, various concentrations of CcLF were used ranging from 25 to 200 μg/mL. This study also looked into whether there could be any acute toxicity and histopathology of the liver, stomach, and kidneys in experimental animals.

Findings/Results

The administration of CcLF significantly inhibited the increase in foot edema volume, and CcLF (EAFCC at 100 mg/kg) considerably decreased rectal temperature and was proportional to the standard drug paracetamol, and significantly inhibited pain sensation in various models. Additionally, CcLF showed strong antioxidant activity, and its administration at a dose limit of 5000 mg/kg/day did not show any toxic effects or death in test animals.

Conclusions and implications

The results of the current confirmed that CcLF has demonstrated anti-inflammatory, antipyretic, analgesic, and antioxidant properties in experimental models, and is practically non-toxic.

Investigation of Anti-inflammatory, Antipyretic and Analgesic Activities of Citrullus colocynthis in Albino Rats through in vivo and Pharmacoinformatics Studies

INTRODUCTION

Hyperpyrexia, algesia and inflammation are pathological disorders which are treated with synthetic as well as herbal medications.

AIMS

The basic aim of the present study is to evaluate the ethnopharmacological activities of phytoconstituents that are present in C. colocynthis (fruit extract) by using in vivo and in silico studies.

METHODS

Thirty-six albino rats were used in our studies with an average weight between 150-170 g. Anti-inflammatory activity was investigated using carrageenan (an extract from a red seaweed) that induced edema in albino rat paws. However, in antipyretic and analgesic activity studies, yeast and acetic acid were used to cause pyrexia or algesia, respectively. Different doses of acetone fruit extract were used to treat inflammation, pyrexia and algesia.

RESULTS

Our results showed that the maximum percentage inhibition of acetonic fruit extract in anti-inflammatory and analgesic activities was observed at 70% and 100%, respectively, with 400 mg/kg doses, and in pyretic activity the maximum inhibitory percentage was 86% with a 100 mg/kg dose. In in silico analysis, we have shown that bioactive compounds (α-spinasterol, ascorbic acid and chlorogenic acid) found in fruit extract have outstanding inhibition properties that involves proteins PTGS2, TLR2 and TRPV4. C. colocynthis fruit extract shows results that are statistically significant (p < 0.005) and comparable to a reference drug. Acetonic fruit extract of C. colocynthis can be used as a natural and safe remedy with no side effects.

CONCLUSION

Both in vivo and in silico studies on chlorogenic acid, ascorbic acid and α-spinasterol have shown that these are inhibitory compounds that can be used for boosting the immune response.

Increased LPS-Induced Fever and Sickness Behavior in Adult Male and Female Rats Perinatally Exposed to Morphine

As a result of the current opioid crisis, the rate of children born exposed to opioids has skyrocketed. Later in life, these children have an increased risk for hospitalization and infection, raising concerns about potential immunocompromise, as is common with chronic opioid use. Opioids can act directly on immune cells or indirectly via the central nervous system to decrease immune system activity, leading to increased susceptibility, morbidity, and mortality to infection. However, it is currently unknown how perinatal opioid exposure (POE) alters immune function. Using a clinically relevant and translatable model of POE, we have investigated how baseline immune function and the reaction to an immune stimulator, lipopolysaccharide, is influenced by in utero opioid exposure in adult male and female rats. We report here that POE potentiates the febrile and neuroinflammatory response to lipopolysaccharide, likely as a consequence of suppressed immune function at baseline (including reduced antibody production). This suggests that POE increases susceptibility to infection by manipulating immune system development, consistent with the clinical literature. Investigation of the mechanisms whereby POE increases susceptibility to pathogens is critical for the development of potential interventions for immunosuppressed children exposed to opioids in utero.

Solar photo-Fenton optimization at neutral pH for microcontaminant removal at pilot plant scale

The increasing occurrence of micropollutants in natural water bodies has medium to long-term effects on both aquatic life and human health. The aim of this study is to optimize the degradation of two pharmaceutical pollutants of emerging concern: amoxicillin and acetaminophen in aqueous solution at laboratory and pilot scale, by solar photo-Fenton process carried out at neutral pH using ethylenediamine-N,N'-disuccinic acid (EDDS) as a complexing agent to maintain iron in solution. The initial concentration of each compound was set at 1 mg/L dissolved in a simulated effluent from a municipal wastewater treatment plant (MWTP). A factorial experimental design and its surface response analysis were used to optimize the operating parameters to achieve the highest initial degradation rate of each target. The evolution of the degradation process was measured by ultra-performance liquid chromatography (UPLC/UV), obtaining elimination rates above 90% for both contaminants. Statistical study showed the optimum concentrations of Fe(III) at 3 mg/L at an Fe-EDDS ratio of 1:2 and 2.75 mg/L H2O2 for the almost complete removal of the target compounds by solar photo-Fenton process. Validation of the experimental design was successfully carried out with actual MWTP effluent spiked with 100 μg/L of amoxicillin and acetaminophen, each at pilot plant scale.

An Evaluation of the Anti-Inflammatory Effects of a Thai Traditional Polyherbal Recipe TPDM6315 in LPS-Induced RAW264.7 Macrophages and TNF-α-Induced 3T3-L1 Adipocytes

TPDM6315 is an antipyretic Thai herbal recipe that contains several herbs with anti-inflammatory and anti-obesity activities. This study aimed to investigate the anti-inflammatory effects of TPDM6315 extracts in lipopolysaccharide (LPS)-induced RAW264.7 macrophages and TNF-α-induced 3T3-L1 adipocytes, and the effects of TPDM6315 extracts on lipid accumulation in 3T3-L1 adipocytes. The results showed that the TPDM6315 extracts reduced the nitric oxide production and downregulated the iNOS, IL-6, PGE₂, and TNF-α genes regulating fever in LPS-stimulated RAW264.7 macrophages. The treatment of 3T3-L1 pre-adipocytes with TPDM6315 extracts during a differentiation to the adipocytes resulted in the decreasing of the cellular lipid accumulation in adipocytes. The ethanolic extract (10 µg/mL) increased the mRNA level of adiponectin (the anti-inflammatory adipokine) and upregulated the PPAR-γ in the TNF-α induced adipocytes. These findings provide evidence-based support for the traditional use of TPDM6315 as an anti-pyretic for fever originating from inflammation. The anti-obesity and anti-inflammatory actions of TPDM6315 in TNF-α induced adipocytes suggest that this herbal recipe could be useful for the treatment of metabolic syndrome disorders caused by obesity. Further investigations into the modes of action of TPDM6315 are needed for developing health products to prevent or regulate disorders resulting from inflammation.

The traditional use of Southern African medicinal plants to alleviate fever and their antipyretic activities

ETHNOPHARMACOLOGICAL RELEVANCE

Multiple plant species are used traditionally in southern Africa to treat fever. This review summarises the traditional use, highlights promising plant species and focuses on validation studies to highlight future areas of research.

AIM OF THE STUDY

This study aimed to critically review the use of southern African plants to alleviate fever. Additionally, an examination of research into those plants was undertaken to highlight gaps in the literature with the aim of stimulating further research in this field.

MATERIALS AND METHODS

Ethnobotanical books, reviews and primary research studies were searched to identify plant species traditionally used to treat fever in southern Africa and to summarise the current knowledge and identify areas requiring further research. This study was non-biased and did not have any taxonomic preferences, nor did it favour any southern African healing systems over the others.

RESULTS

The traditional therapeutic uses of 203 southern African plant species to alleviate fever were recorded. Leaves and roots/bulbs/rhizomes were the most commonly used plant part, and they were most commonly prepared as decoctions or infusions and consumed orally. Notably, only twenty-two species (∼11% of the identified species) have been scientifically evaluated for antipyretic properties, with substantially fewer mechanistic studies evident.

CONCLUSIONS

Despite the availability of ethnobotanical records, the antipyretic properties of southern African medicinal plants are poorly reported. Indeed, the efficacy of most plants is yet to be verified and very few mechanistic studies are available.

Natural-Derived COX-2 Inhibitors as Anticancer Drugs: A Review of their Structural Diversity and Mechanism of Action

Cyclooxygenase-2 (COX-2) is a key-type enzyme playing a crucial role in cancer development, making it a target of high interest for drug designers. In the last two decades, numerous selective COX-2 inhibitors have been approved for various clinical conditions. However, data from clinical trials propose that the prolonged use of COX-2 inhibitors is associated with life-threatening cardiovascular side effects. The data indicate that a slight structural modification can help develop COX-2 selective inhibitors with comparative efficacy and limited side effects. In this regard, secondary metabolites from natural sources offer great hope for developing novel COX-2 inhibitors with potential anticancer activity. In recent years, various nature-derived organic scaffolds are being explored as leads for developing new COX-2 inhibitors. The current review attempts to highlight the COX-2 inhibition activity of some naturally occurring secondary metabolites, concerning their capacity to inhibit COX-1 and COX-2 enzymes and inhibit cancer development, aiming to establish a structure-activity relationship.

Assessing the pyrogenicity of whole influenza virus particle vaccine in cynomolgus macaques

Among inactivated influenza vaccines, the whole virus particle vaccine (WPV) elicits superior priming responses to split virus vaccine (SV) in efficiently inducing humoral and cellular immunity. However, there is concern for undesired adverse events such as fever for WPV due to its potent immunogenicity. Therefore, this study investigated the febrile response induced by subcutaneous injection with quadrivalent inactivated influenza vaccines of good manufacturing grade for pharmaceutical or investigational products in cynomolgus macaques. Body temperature was increased by 1 °C-2 °C for 6-12 h after WPV administration at the first vaccination but not at the second shot, whereas SV did not affect body temperature at both points. Given the potent priming ability of WPV, WPV-induced fever may be attributed to immune responses that uniquely occur during priming. Since WPV-induced fever was blunted by pretreatment with indomethacin (a cyclooxygenase inhibitor), the febrile response by WPV is considered to depend on the increase in prostaglandins synthesized by cyclooxygenase. In addition, WPV, but not SV, induced the elevation of type I interferons and monocyte chemotactic protein 1 in the plasma; these factors may be responsible for pyrogenicity caused by WPV, as they can increase prostaglandins in the brain. Notably, sufficient antibody responses were acquired by half the amount of WPV without causing fever, suggesting that excessive immune responses to trigger the febrile response is not required for acquired immunity induction. Thus, we propose that WPV with a reduced antigen dose should be evaluated for potential clinical usage, especially in naïve populations.

Huanglian Jiedu Decoction Exerts Antipyretic Effect by Inhibiting MAPK Signaling Pathway

AIM

The aim of this study was to explore the antipyretic effect and potential mechanism of Huanglian Jiedu Decoction (HLJDD) on LPS-induced fever in rats.

MATERIALS AND METHODS

The fever rat model was established by LPS. Anal temperature of rats was measured every 1 hour after modeling. TNF-α, IL-6, PGE2, and cAMP in rat serum or hypothalamus tissue were detected by ELISA kit. In order to explore the potential active ingredients and mechanism of antipyretic effect of HLJDD, we predicted the underlying antipyretic mechanism by using network pharmacology and then verified its mechanism by Western Blotting.

RESULTS

The results showed that HLJDD can alleviate LPS-induced fever in rats. The expression levels of TNF-α, IL-6, PGE2, and cAMP in the treatment group were significantly lower than those in the model group. Western Blotting results showed that the protein expression of p-ERK, p-JNK, and p-P38 was significantly inhibited.

CONCLUSION

The findings suggest that HLJDD has a good antipyretic effect on LPS-induced fever in rats, which may be closely related to the inhibition of MAPK signaling pathway.

Thyroid hormone suppression in feeder pigs following polymicrobial or porcine reproductive and respiratory syndrome virus-2 challenge

Thyroid hormones are powerful regulators of growth, development, and basal metabolic rate and can be dysregulated under conditions of severe stress or illness. To understand the role of these hormones in porcine disease response, serum samples were obtained from three batches of nursery-aged pigs (n = 208) exposed to a natural polymicrobial disease challenge with an array of bacterial and viral pathogens. Levels of total thyroxin (T4) and triiodothyronine (T3) assessed in sera by radioimmunoassay, decreased significantly by 14 days post-exposure (DPE). Levels of T3 partially rebounded by 48 DPE, while T4 levels remain depressed. Post-exposure T3 and T4 levels were positively correlated with acute and long-term average daily gain (ADG). Cross-sectional sampling of animals maintained at the high health source farms, showed no equivalent change in either hormone when managed under standard industrial conditions. To further elucidate the effect of porcine reproductive and respiratory syndrome virus (PRRSV)-infection on thyroid hormone levels, archived sera over 42 days post inoculation (DPI) from nursery pigs (N = 190) challenged with one of two PRRSV2 strains by the PRRS Host Genetics Consortium were similarly assessed, with animals selected in a two-by-two design, to investigate biological extremes in ADG and viral load (VL). All animals showed a similar decrease in both thyroid hormones reaching a minimum at 7 DPI and returning to near pre-challenge levels by 42 DPI. Post-challenge T3 and T4 levels were significantly greater in high ADG groups, with no significant association with VL or strain. The results of this study demonstrate porcine susceptibility to thyroid disruption in response to disease challenge and demonstrate a relationship between this response and growth performance.

Dissecting the novel mechanism of reduning injection in treating Coronavirus Disease 2019 (COVID-19) based on network pharmacology and experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Reduning injection (RDNI) is a patented Traditional Chinese medicine that contains three Chinese herbal medicines, respectively are the dry aboveground part of Artemisia annua L., the flower of Lonicera japonica Thunb., and the fruit Gardenia jasminoides J.Ellis. RDNI has been recommended for treating Coronavirus Disease 2019 (COVID-19) in the "New Coronavirus Pneumonia Diagnosis and Treatment Plan".

AIM OF THE STUDY

To elucidate and verify the underlying mechanisms of RDNI for the treatment of COVID-19.

METHODS

This study firstly performed anti-SARS-CoV-2 experiments in Vero E6 cells. Then, network pharmacology combined with molecular docking was adopted to explore the potential mechanisms of RDNI in the treatment for COVID-19. After that, western blot and a cytokine chip were used to validate the predictive results.

RESULTS

We concluded that half toxic concentration of drug CC50 (dilution ratio) = 1:1280, CC50 = 2.031 mg crude drugs/mL (0.047 mg solid content/mL) and half effective concentration of drug (EC50) (diluted multiples) = 1:25140.3, EC50 = 103.420 μg crude drugs/mL (2.405 μg solid content/mL). We found that RDNI can mainly regulate targets like carbonic anhydrases (CAs), matrix metallopeptidases (MMPs) and pathways like PI3K/AKT, MAPK, Forkhead box O s and T cell receptor signaling pathways to reduce lung damage. We verified that RDNI could effectively inhibit the overexpression of MAPKs, PKC and p65 nuclear factor-κB. The injection could also affect cytokine levels, reduce inflammation and display antipyretic activity.

CONCLUSION

RDNI can regulate ACE2, Mpro and PLP in COVID-19. The underlying mechanisms of RDNI in the treatment for COVID-19 may be related to the modulation of the cytokine levels and inflammation and its antipyretic activity by regulating the expression of MAPKs, PKC and p65 nuclear factor NF-κB.

Distinct Modulatory Effects of Fever-Range Hyperthermia on the Response of Breast Cancer Cells and Macrophages to Mistletoe (Viscum album L.) Extract

Heat utility as a critical component of fever is often ignored, although the symptom is observed in many medical conditions. Mistletoe extract (ME) is an adjunctive medication prescribed to cancer patients. The increase in body temperature is frequently observed in patients following ME administration. Nevertheless, the impact of this fever on the effectiveness of therapy is unknown. Therefore, we aimed to investigate the effect of fever-range temperatures on ME-treated breast cancer cells and macrophages. The cells were simultaneously stimulated with ME and subjected to fever-range hyperthermia (FRH; 39 °C or 41 °C). After co-treatment, the cell viability, generation of reactive oxygen species (ROS), cell cycle distribution, and production of pro-inflammatory factors (interleukin (IL)-1β, IL-6, and cyclooxygenase (COX)-2) were evaluated. The results showed that the exposure of ME-treated breast cancer cells to FRH at 39 °C resulted in a slight decrease in their viability, whereas FRH of 41 °C enhanced this effect. Only FRH of 41 °C induced minor changes in ROS level in ME-treated breast cancer cell lines. In ME-treated macrophages, FRH stimulated cell proliferation. The cell cycle distribution analysis showed a difference between cells cultured at 39 °C and 41 °C in all examined cell lines. Moreover, hyperthermia at 41 °C completely inhibited the ME-induced increase in IL-1β and IL-6 expression in MCF-7 breast cancer cells, whereas this effect was not observed in 4T1 breast cancer cells. In contrast, in ME-treated macrophages, FRH of 41 °C strongly up-regulated expression of the pro-inflammatory factors. We conclude that fever is an important component of ME therapy that differentially affects cancer and immune cells.

Fever and Antipyretic Supported by Traditional Chinese Medicine: A Multi-Pathway Regulation

The coronavirus disease, 2019 (COVID-19), has spread rapidly around the world and become a major public health problem facing the world. Traditional Chinese medicine (TCM) has been fully committed to treat COVID-19 in China. It improved the clinical symptoms of patients and reduced the mortality rate. In light of the fever was identified as one of leading clinical features of COVID-19, this paper will first analyze the material basis of fever, including pyrogenic cytokines and a variety of the mediators of fever. Then the humoral and neural pathways of fever signal transmission will be described. The scattered evidences about fever recorded in recent years are connected in series. On this basis, the understanding of fever is further deepened from the aspects of pathology and physiology. Finally, combining with the chemical composition and pharmacological action of available TCM, we analyzed the mechanisms of TCMs to play the antipyretic effect through multiple ways. So as to further provide the basis for the research of antipyretic compound preparations of TCMs and explore the potential medicines for the prevention and treatment of COVID-19.

Mitochondrial pyruvate carrier as a key regulator of fever and neuroinflammation

The mitochondrial pyruvate carrier (MPC) is an inner-membrane transporter that facilitates pyruvate uptake from the cytoplasm into mitochondria. We previously reported that MPC1 protein levels increase in the hypothalamus of animals during fever induced by lipopolysaccharide (LPS), but how this increase contributes to the LPS responses remains to be studied. Therefore, we investigated the effect of UK 5099, a classical MPC inhibitor, in a rat model of fever, on hypothalamic mitochondrial function and neuroinflammation in LPS-stimulated preoptic area (POA) primary microcultures. Intracerebroventricular administration of UK 5099 reduced the LPS-induced fever. High-resolution respirometry revealed an increase in oxygen consumption and oxygen flux related to ATP synthesis in the hypothalamic homogenate from LPS-treated animals linked to mitochondrial complex I plus II. Preincubation with UK 5099 prevented the LPS-induced increase in oxygen consumption, ATP synthesis and spare capacity only in complex I-linked respiration and reduced mitochondrial H₂O₂ production. In addition, treatment of rat POA microcultures with UK 5099 reduced the secretion of the proinflammatory and pyrogenic cytokines TNFα and IL-6 as well as the immunoreactivity of inflammatory transcription factors NF-κB and NF-IL6 four hours after LPS stimulation. These results suggest that the regulation of mitochondrial pyruvate metabolism through MPC inhibition may be effective in reducing neuroinflammation and fever.

Are corticosteroids or end-stage renal failure associated with an afebrile presentation of Gram-negative bacteraemia?

OBJECTIVES

Assertions regarding afebrile presentation of sepsis frequently lead to superfluous antibiotic treatment. This study aimed to identify the risk factors for afebrile presentation of bacteraemia, focusing on glucocorticoid (GC) treatment and end-stage renal disease (ESRD).

METHODS

This retrospective cohort study included all patients with bacteraemia caused by common Gram-negative bacteria in one hospital. The exposure variables were GC treatment, administered for at least 48 hours before bacteraemia onset, and ESRD, defined as patients undergoing dialysis. Risk factors were assessed for afebrile presentation, defined as temperature between 36.0-37.7°C for all measurements, 48 hours prior to blood culture collection. Analyses were subgrouped by community-onset and hospital-acquired Gram-negative bacteraemia (GNB). Propensity score (PS)-weighted multivariate analyses were conducted.

RESULTS

Of 4179 patients with GNB, 1090 (26.1%) presented without fever before blood culture collection. In community-onset GNB, GC treatment was significantly associated with afebrile presentation, PS-weighted OR 1.42 (95% CI 1.25-1.61), absolute risk increase 7% (95% CI 4.3-9.8%), while ESRD was not. For hospital-acquired GNB, ESRD was significantly associated with afebrile presentation (OR 1.53; 95% CI 1.25-1.86; absolute risk increase 8.5%; 95% CI 4.4-13.1%); GC was not. Other risk factors for afebrile presentation in both subgroups included increasing Charlson comorbidity score, bacteraemia with non-fermenters Pseudomonas aeruginosa or Stenotrophomonas maltophilia (compared with Enterobacteriaceae), and lower albumin levels. Aging was not associated with afebrile presentation of GNB.

CONCLUSION

Although significant associations between GC and ESRD and afebrile presentation of GNB were observed, they were different in community-onset and hospital-acquired GNBs, and absolute risk increases were small.

Intermittent binge-like ethanol exposure during adolescence attenuates the febrile response by reducing brown adipose tissue thermogenesis in rats

Ethanol (EtOH) consumption is a primary health risk worldwide, which generally starts during adolescence in a binge pattern (i.e., the episodic consumption of high amounts). Binge EtOH consumption can lead to modifications of the innate and adaptive immune responses, including fever. The present study evaluated the febrile response that was induced by lipopolysaccharide (LPS) and prostaglandins E₂ (PGE₂) and the mechanisms of thermoregulation in adolescent rats that were exposed to EtOH in a binge-like pattern. Male Wistar rats were treated with an intraperitoneal (i.p.) injection of EtOH or saline on postnatal days (PND) 25, 26, 29, 30, 33, 34, 37, and 38. On PND 51, they received a pyrogenic challenge with LPS (i.p.) or PGE₂ (intracerebroventricular) to induce a febrile response. Interscapular brown adipose tissue (BAT) mass and uncoupling protein (UCP) activity in isolated mitochondria were evaluated on PND 51. The rats were then subjected to cold challenges to analyze adaptive thermogenesis. Intermittent EtOH exposure during adolescence impaired the LPS- and PGE₂-induced febrile response 12 days after the end of EtOH exposure. Ethanol exposure decreased interscapular BAT mass, oxygen consumption, and UCP activity in isolated mitochondria, resulting in an impairment in thermogenesis at 5 °C. No morphological changes in BAT were observed. These findings indicate that binge-like EtOH exposure during adolescence impairs thermoregulation by reducing BAT mass and function. This reduction may last for a prolonged period of time after the cessation of EtOH exposure and may affect both cold defenses and the febrile response during the development of infectious diseases.

Temperature regulation in women: Effects of the menstrual cycle

Core body temperature changes across the ovulatory menstrual cycle, such that it is 0.3°C to 0.7°C higher in the post-ovulatory luteal phase when progesterone is high compared with the pre-ovulatory follicular phase. This temperature difference, which is most evident during sleep or immediately upon waking before any activity, is used by women as a retrospective indicator of an ovulatory cycle. Here, we review both historical and current literature aimed at characterizing changes in core body temperature across the menstrual cycle, considering the assessment of the circadian rhythm of core body temperature and thermoregulatory responses to challenges, including heat and cold exposure, exercise, and fever. We discuss potential mechanisms for the thermogenic effect of progesterone and the temperature-lowering effect of estrogen, and discuss effects on body temperature of exogenous formulations of these hormones as contained in oral contraceptives. We review new wearable temperature sensors aimed at tracking daily temperature changes of women across multiple menstrual cycles and highlight the need for future research on the validity and reliability of these devices. Despite the change in core body temperature across the menstrual cycle being so well identified, there remain gaps in our current understanding, particularly about the underlying mechanisms and microcircuitry involved in the temperature changes.

Immune-mediated febrile response in female rats: Role of central hypothalamic mediators

Lipopolysaccharide (LPS) induces fever through cytokines like receptor-activator of nuclear factor κB ligand (RANKL), triggering mediators like prostaglandins (PG), endothelin-1 (ET-1), corticotrophin-releasing factor (CRF), substance P (SP) and endogenous opioids. LPS-induced fever is reduced in females compared with males except in ovariectomized (OVX) females which show increased fever mediated by PG. The present study aimed to identify the mediators involved in fever in intact and OVX female rats. Fever was induced with LPS (50 μg/kg) intraperitoneally or CRF (2.5 μg), ET-1 (1 pg), morphine (10 μg) and SP (500 ng) intracerebroventricularly in sham-operated and OVX rats. The role of RANKL was evaluated with osteoprotegerin (OPG, 1 μg, intracerebroventricularly). Expression of RANK, CRFI/II, ETB, μ-opioid (MOR) and NK1 receptors was evaluated by confocal microscopy. Besides LPS, only morphine induced fever in OVX rats while all mediators induced fever in sham-operated animals. OPG abolished LPS-induced fever in OVX but not sham-operated animals. Overall, fever involves similar central mediators in cycling females and males but only morphine induced fever in OVX females. Importantly, RANK/RANKL participates in LPS-induced fever in OVX females, as in males but not in cycling females.

New Insights into the Role of Glutathione in the Mechanism of Fever

Glutathione is one of the most important and potent antioxidants. The development of pharmacological compounds that can either increase or decrease glutathione concentrations has allowed investigation into the role of glutathione in various biological processes, including immune responses. Recent findings have shown that glutathione not only affects certain factors involved in immunological processes but also modifies complex immune reactions such as fever. Until recently, it was not known why some patients do not develop fever during infection. Data suggest that fever induction is associated with oxidative stress; therefore, antioxidants such as glutathione can reduce pyrexia. Surprisingly, new studies have shown that low glutathione levels can also inhibit fever. In this review, we focus on recent advances in this area, with an emphasis on the role of glutathione in immune responses accompanied by fever. We describe evidence showing that disturbed glutathione homeostasis may be responsible for the lack of fever during infections. We also discuss the biological significance of the antipyretic effects produced by pharmacological glutathione modulators.

High Serum Level of IL-17 in Patients with Chronic Obstructive Pulmonary Disease and the Alpha-1 Antitrypsin PiZ Allele

Chronic obstructive pulmonary disease (COPD) is multifactorial disease, which is characterized by airflow limitation and can be provoked by genetic factors, including carriage of the PiZ allele of the protease inhibitor (Pi) gene, encoding alpha-1 antitrypsin (A1AT). Both homozygous and heterozygous PiZ allele carriers can develop COPD. It was found recently that normal A1AT regulates cytokine levels, including IL-17, which is involved in COPD progression. The aim of this study was to determine whether homozygous or heterozygous PiZ allele carriage leads to elevated level of IL-17 and other proinflammatory cytokines in COPD patients. Materials and Methods. Serum samples and clinical data were obtained from 44 COPD patients, who included 6 PiZZ, 8 PiMZ, and 30 PiMM A1AT phenotype carriers. Serum concentrations of IL-17, IL-6, IL-8, IFN-γ, and TNF-α were measured by the enzyme-linked immunosorbent assay (ELISA). All A1AT phenotypes were verified by narrow pH range isoelectrofocusing with selective A1AT staining. A turbidimetric method was used for quantitative A1AT measurements. Results. COPD patients with both PiZZ and PiMZ phenotypes demonstrated elevated IL-17 and decreased IFN-γ levels in comparison to patients with the PiMM phenotype of A1AT. Thereafter, the ratio IL-17/IFN-γ in PiZZ and PiMZ groups greatly exceeded the values of the PiMM group. Homozygous PiZ allele carriers also had significantly higher levels of IL-6 and lower levels of IL-8, and IL-6 values correlated negatively with A1AT concentrations. Conclusions. The presence of the PiZ allele in both homozygous and heterozygous states is associated with altered serum cytokine levels, including elevated IL-17, IL-17/IFN-γ ratio, and IL-6 (only PiZZ), but lower IFN-γ and IL-8.

Do Bacteremic patients with end-stage renal disease have a fever when presenting to the emergency department? A paired, retrospective cohort study

Background

Fever is a common symptom when patients present to Emergency Departments. It is unclear if the febrile response of bacteremic hemodialysis-dependent patients differs from bacteremic patients not receiving hemodialysis. The objective of this study was to compare Emergency Departments triage temperatures of patients with and without hemodialysis-dependent end-stage rental disease who have Staphylococcus aureus bacteremia and determine the incidence of afebrile S. aureus bacteremia.

Methods

Paired, retrospective cohort study of 37 patients with and 37 patients without hemodialysis hospitalized with Methicillin-resistant or Methicillin-susceptible S. aureus bacteremia. Emergency Department triage temperatures were reviewed for all patients, as were potential confounding variables.

Results

54% (95% CI, 38–70%) and 82% (95% CI 65–91%) of hemodialysis and non-hemodialysis patients did not have a detectable fever (<100.4 °F) at triage. Triage temperatures were 100.5 °F (95% CI 99.9–101.2 °F) and 99.0 °F (95% CI 98.4–99.6 °F) in the hemodialysis and non-hemodialysis cohorts, respectively (p < 0.001). Triage temperature in patients with and without diabetes mellitus was 99.2 °F (95% CI 98.4–99.9 °F) and 100.4 °F (95% CI 99.7–101.0 °F), respectively (p = 0.03). We were unable to detect a significant effect of diabetes mellitus and other potential confounding variables on differences in temperature between the hemodialysis and non-hemodialysis cohorts (all interactions p > 0.19).

Conclusions

Hemodialysis-dependent patients with S. aureus bacteremia had significantly higher temperatures than non- hemodialysis-dependent end stage renal disease patients but more than half of patients were without detectable fever at triage, possibly reflecting use of insensitive methods for measuring temperature. Absence of fever at presentation to the Emergency Department should not delay blood culture acquisition in patients who are at increased risk of S. aureus bacteremia.

Antipyretic, anti-inflammatory and analgesic activities of Periplaneta americana extract and underlying mechanisms

Periplaneta americana is a common traditional Chinese medicinal material which has been used to treat arthritis, fever, aches, pains, and inflammation of the extremities for several hundred years. However, little scientific data exists in literature to support its use. The purpose of this study was to evaluate the antipyretic, anti-inflammatory and analgesic activities of Periplaneta americana extract (PAE) and explore its underlying mechanism. The antipyretic, anti-inflammatory and analgesic activities were evaluated by LPS-induced fever, carrageenan-induced paw edema, abdominal writhing, hot plate and formalin tests, respectively. The mechanism of action was explored by antioxidant activity analysis, inflammatory cytokines expression and febrile mediator measurement, and pathway activation analysis. The results from UHPLC-HRMS indicated that the extract was found to contain dopamine, coumarin, dipeptide, vitamin, organic acid, amino acid and its metabolites, and other organic compounds. PAE showed in a dose-dependent manner antioxidant activity and reduced the protein production and mRNA expression of NO, IL-1β, IL-6, and TNF-α in RAW 264.7 cells in vitro. Moreover, PAE significantly and dose-dependently inhibited the writhing responses and licking time in formalin tests, increased response latency in the hot plate test, reduced carrageenan-induced paw edema and inflammation in mice, decreased LPS-induced rT increase in rats. Furthermore, PAE treatment markedly inhibited the increase in the levels of NO, IL-6, IL-1β, TNF-α, PGE₂ and cAMP in plasma of fevered rat, greatly suppressed the activation of inflammatory response pathway and the change of MDA and GSH concentration, MPO and SOD activity as well as FRAP capacity in paw induced by carrageenan injection. In conclusion, the findings suggested that PAE produced potential antinociceptive, anti-inflammatory and antipyretic effects by reducing production of endogenous inflammatory mediators and blocking the MAPK/NF-κB signaling pathway which support the claim for its traditional use in the treatment of various diseases.

Cytoglobin Attenuates Neuroinflammation in Lipopolysaccharide-Activated Primary Preoptic Area Cells via NF-κB Pathway Inhibition

Cytoglobin (Cygb) is a hexacoordinate protein, associated with the transport of oxygen, nitric oxide scavenging, tumor suppression and protection against oxidative stress and inflammation. This protein is expressed in brain areas including the preoptic area (POA) of the anterior hypothalamus, the region responsible for the regulation of body temperature. In this study, we show that Cygb is upregulated in the rat hypothalamus 2.5 h and 5 h after intravenous administration of lipopolysaccharide (LPS). We investigated the effect of treatment with Cygb in POA primary cultures stimulated with LPS for 4 h. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) were measured and the results showed that Cygb reduced the concentrations of both cytokines. We further observed a decrease in immunoreactivity of the inflammatory transcription factor nuclear factor-κB (NF-κB), but not NF-IL6 and STAT3, in the nucleus of Cygb-treated POA cells. These findings suggest that Cygb attenuates the secretion of IL-6 and TNF-α in LPS-stimulated POA primary cultures via inhibition of the NF-κB signaling pathway, indicating that this protein might play an important role in the control of neuroinflammation and fever.

Role of CINC-1 and CXCR2 receptors on LPS-induced fever in rats

The classic model of fever induction is based on the administration of lipopolysaccharide (LPS) from Gram-negative bacteria in experimental animals. LPS-induced fever results in the synthesis/release of many mediators that assemble an LPS-fever cascade. We have previously demonstrated that cytokine-induced neutrophil chemoattractant (CINC)-1, a Glu-Leu-Arg (ELR) + chemokine, centrally administered to rats, induces fever and increases prostaglandin E₂ in the cerebrospinal fluid. We now attempt to investigate the involvement of CINC-1 and its functional receptor CXCR2 on the fever induced by exogenous and endogenous pyrogens in rats. We also investigated the effect of reparixin, an allosteric inhibitor of CXCR1/CXCR2 receptors, on fever induced by either systemic administration of LPS or intracerebroventricular injection of CINC-1, as well as TNF-α, IL-1β, IL-6, or ET-1, known mediators of febrile response. Our results show increased CINC-1 mRNA expression in the liver, hypothalamus, CSF, and plasma following LPS injection. Moreover, reparixin administered right before CINC-1 or LPS abolished the fever induced by CINC-1 and significantly reduced the response induced by LPS. In spite of these results, reparixin does not modify the fever induced by IL-1β, TNF-α, and IL-6, but significantly reduces ET-1-induced fever. Therefore, it is plausible to suggest that CINC-1 might contribute to LPS-induced fever in rats by activating CXCR2 receptor on the CNS. Moreover, it can be hypothesized that CINC-1 is placed upstream TNF-α, IL-1β, and IL-6 among the prostaglandin-dependent fever-mediator cascade and amidst the prostaglandin-independent synthesis pathway of fever.

Label-free quantitative proteomics of rat hypothalamus under fever induced by LPS and PGE2

Fever is a brain-mediated increase in body temperature mainly during inflammatory or infectious challenges. Although there is considerable data regarding the inflammation pathways involved in fever, metabolic alterations necessary to orchestrate the complex inflammatory response are not totally understood. We performed proteomic analysis of rat hypothalamus using label-free LC-MS/MS in a model of fever induced by lipopolysaccharide (LPS) or prostaglandin E₂ (PGE₂). In total, 7021 proteins were identified. As far as we know, this is the largest rat hypothalamus proteome dataset available to date. Pathway analysis showed proteins from both stimuli associated with inflammatory and metabolic pathways. Concerning metabolic pathways, rats exposed to LPS or PGE₂ presented lower relative abundance of proteins involved in glycolysis, pentose phosphate pathway and tricarboxylic acid cycle. Mitochondrial function may also be altered by both stimuli because significant downregulation of several proteins was found, mainly in complexes I and IV. LPS was able to induce downregulation of important proteins in the enzymatic antioxidant system, thereby contributing to oxidative stress. The results offered comprehensive information about fever responses and helped to reveal new insights into proteins potentially involved in inflammatory signaling and metabolic changes in the hypothalamus during systemic LPS and central PGE₂ administration.

SIGNIFICANCE

The evolutionary persistence of fever, despite the elevated cost for maintenance of this response, suggests that elevation in core temperature may represent an interesting strategy for survival. Fever response is achieved through the integrated behavioral, physiological, immunological and biochemical processes that determine the balance between heat generation and elimination. The development of such complex response arouses interest in studying how the cell metabolism responds or even contributes to promote fever. Our results offered comprehensive information about fever responses, including metabolic and inflammatory pathways, providing new insights into candidate proteins potentially involved in inflammatory signaling and metabolic changes in the hypothalamus during fever induced by systemic LPS and central PGE₂ perturbation.

Central mediators of the zymosan-induced febrile response

BACKGROUND

Zymosan is a fungal cell wall protein-carbohydrate complex that is known to activate inflammatory pathways through the Toll-like receptors and is commonly used to induce fever. Nevertheless, the central mediators that are involved in the zymosan-induced febrile response are only partially known.

METHODS

The present study evaluated the participation of prostaglandins, substance P, endothelin-1 (ET-1), and endogenous opioids (eOPs) in the zymosan-induced febrile response by using inhibitors and antagonists in male Wistar rats.

RESULTS

Both nonselective (indomethacin) and selective (celecoxib) cyclooxygenase inhibitors reduced the febrile response induced by an intraperitoneal (i.p.) injection of zymosan. Indomethacin also blocked the increase in the prostaglandin E2 levels in the cerebrospinal fluid. An intracerebroventricular injection of the neurokinin-1, ETB, and μ-opioid receptor antagonists also reduced the febrile response induced by the i.p. injected zymosan. Moreover, the μ-opioid receptor antagonist CTAP also reduced the febrile response induced by intra-articular injection of zymosan.

CONCLUSIONS

These results demonstrate that prostaglandins, substance P, ET-1, and eOPs are central mediators of the zymosan-induced febrile response.

The Neurokinin-1 Receptor Contributes to the Early Phase of Lipopolysaccharide-Induced Fever via Stimulation of Peripheral Cyclooxygenase-2 Protein Expression in Mice

Neurokinin (NK) signaling is involved in various inflammatory processes. A common manifestation of systemic inflammation is fever, which is usually induced in animal models with the administration of bacterial lipopolysaccharide (LPS). A role for the NK1 receptor was shown in LPS-induced fever, but the underlying mechanisms of how the NK1 receptor contributes to febrile response, especially in the early phase, have remained unknown. We administered LPS (120 µg/kg, intraperitoneally) to mice with the Tacr1 gene, i.e., the gene encoding the NK1 receptor, either present (Tacr1+/+ ) or absent (Tacr1-/- ) and measured their thermoregulatory responses, serum cytokine levels, tissue cyclooxygenase-2 (COX-2) expression, and prostaglandin (PG) E2 concentration. We found that the LPS-induced febrile response was attenuated in Tacr1-/- compared to their Tacr1+/+ littermates starting from 40 min postinfusion. The febrigenic effect of intracerebroventricularly administered PGE2 was not suppressed in the Tacr1-/- mice. Serum concentration of pyrogenic cytokines did not differ between Tacr1-/- and Tacr1+/+ at 40 min post-LPS infusion. Administration of LPS resulted in amplification of COX-2 mRNA expression in the lungs, liver, and brain of the mice, which was statistically indistinguishable between the genotypes. In contrast, the LPS-induced augmentation of COX-2 protein expression was attenuated in the lungs and tended to be suppressed in the liver of Tacr1-/- mice compared with Tacr1+/+ mice. The Tacr1+/+ mice responded to LPS with a significant surge of PGE2 production in the lungs, whereas Tacr1-/- mice did not. In conclusion, the NK1 receptor is necessary for normal fever genesis. Our results suggest that the NK1 receptor contributes to the early phase of LPS-induced fever by enhancing COX-2 protein expression in the periphery. These findings advance the understanding of the crosstalk between NK signaling and the "cytokine-COX-2-prostaglandin E2" axis in systemic inflammation, thereby open up the possibilities for new therapeutic approaches.

Rectal temperature in the first five hours after hypoxia-ischemia critically affects neuropathological outcomes in neonatal rats

BackgroundHyperthermia after hypoxia-ischemia (HI) in newborn infants is associated with worse neurological outcomes. Loss of thermoregulation may also be associated with greater injury.MethodsIn the postnatal-day 7 (P7) rat, the effect of 5 h of graded hyperthermia (38 °C or 39 °C) immediately after unilateral HI was compared with normothermia (NT, 37 °C) and therapeutic hypothermia (TH, 32 °C). Early (negative geotaxis) and late (staircase test) behavioral testing was performed, as well as neuropathology scoring in adulthood. Separately, P7 rats were exposed to HI, and individual nesting temperatures were monitored before analysis of neuropathology at P14.ResultsMortality increased as temperature was increased from 38 °C (0%) to 39 °C (50%) after HI. Hyperthermia also resulted in early behavioral deficits compared with NT. In adulthood, pathology scores in the thalamus, basal ganglia, cortex, and hippocampus increased as post-hypoxic temperature increased above NT. Significant global neuroprotection was seen in the TH group. However, no significant difference was seen between HI groups in the staircase test. One hour after HI, the core temperature of pups was inversely correlated with global pathology scores at P14.ConclusionEarly temperature is a significant determinant of injury after experimental HI. Spontaneous decreases in core temperature after HI may confound neuroprotection studies.

Increase of reactive oxygen species in different tissues during lipopolysaccharide-induced fever and antipyresis: an electron paramagnetic resonance study

Fever is a regulated increase in body temperature and a component of the acute-phase response, triggered mainly after the invasion of pathogens in the body. Reactive oxygen species (ROS) are generated during the physiological and pathological processes, and can act as both signalling molecules as well as promoters of oxidative stress. Male Wistar rats, pretreated with oral doses of acetaminophen, celecoxib, dipyrone, or ibuprofen 30 min before an intravenous lipopolysaccharide (LPS) or sterile saline injection, showed a reduced febrile response in all animals tested. The formation of ROS in the fresh blood, liver, brown adipose tissue (BAT), and hypothalamus of febrile and antipyretic-treated animals was assessed by electron paramagnetic resonance using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH). While the CM^• concentrations remained unaltered in the blood samples examined 5 h after the induction of fever, we found increased CM^• levels in the liver (in µM, saline: 290 ± 42; LPS: 512 ± 34), BAT (in µM, saline: 509 ± 79, LPS: 855 ± 79), and hypothalamus (in µM, saline: 292 ± 35; LPS: 467 ± 8) at the same time point. Importantly, none of the antipyretics were seen to alter the CM^• accumulation profile. Data from this study suggest that there is an increased formation of ROS in the different tissues during fever, which may cause oxidative stress, and that the antipyretics tested do not interfere with ROS production.

Thermal and cytokine responses to endotoxin challenge during early life

Sudden infant death syndrome (SIDS) remains the leading cause of infant mortality beyond the neonatal period. An increase in body temperature as a result of high environmental temperature, overwrapping of infants, and (or) infection are associated with SIDS. Endotoxins such as lipopolysaccharide (LPS) and heat stress may perturb cardiorespiratory function and thermoregulation. Although LPS-mediated body temperature and cytokine responses are well documented in older animals, the capacity of LPS to induce fever and cytokine response in young rats remains unclear. Therefore, we sought to investigate the acute effects of LPS on body temperature and cytokine concentrations in rat pups. Postnatal day 7 rat pups were divided into 3 groups: Group 1, rats were administered LPS intraperitoneally (200 μg/kg); Group 2, rats received saline at volume equal to that administered in the LPS group; Group 3, rats received no treatment. Pups were placed in custom-made chambers maintained at ambient temperature of 33 °C. Body surface temperature was continuously monitored for 4 h. Thereafter, the rats were euthanized and serum was collected for cytokine analysis. We demonstrate that LPS treatment increased MIP-1α, IL-10, MCP-1, IP-10, fractalkine, and TNF-α with no concurrent rise in body surface temperature. Although neonatal rats produced an array of cytokines in response to LPS, there was no evidence of fever.

The relevance of kalikrein-kinin system via activation of B2 receptor in LPS-induced fever in rats

PURPOSE

This study evaluated the involvement of endogenous kallikrein-kinin system and the bradykinin (BK) B₁ and B₂ receptors on LPS- induced fever and the POA cells involved in this response.

MATERIAL AND METHODS

Male Wistar rats received either i.v. (1 mg/kg), i.c.v. (20 nmol) or i.h. (2 nmol) injections of icatibant (B₂ receptor antagonist) 30 or 60 min, respectively, before the stimuli. DALBK (B₁ receptor antagonist) was given either 15min before BK (i.c.v.) or 30 min before LPS (i.v.). Captopril (5 mg/kg, sc.,) was given 1 h prior LPS or BK. Concentrations of BK and total kininogenon CSF, plasma and tissue kallikrein were evaluated. Rectal temperatures (rT) were assessed by telethermometry. Ca⁺⁺ signaling in POA cells was performed in rat pup brain tissue microcultures.

RESULTS

Icatibant reduced LPS fever while, captopril exacerbated that response, an effect abolished by icatibant. Icatibant (i.h.) reduced fever to BK (i.h.) but not that induced by LPS (i.v.). BK increased intracellular calcium concentration in neurons and astrocytes. LPS increased levels of bradykinin, tissue kallikrein and total kininogen. BK (i.c.v.) increased rT and decreased tail skin temperature. Captopril potentiated BK-induced fever an effect abolished by icatibant. DALBK reduced the fever induced by BK. BK (i.c.v.) increased the CSF PGE₂concentration. Effect abolished by indomethacin (i.p.).

CONCLUSIONS

LPS activates endogenous kalikrein-kinin system leading to production of BK, which by acting on B₂-receptors of POA cells causes prostaglandin synthesis that in turn produces fever. Thus, a kinin B₂-receptor antagonist that enters into the brain could constitute a new and interesting strategy to treat fever.

Virtual screening and biological evaluation of novel antipyretic compounds

Due to the absence of safety of the antipyretics to patients with cardiovascular dysfunction, new targets to treat inflammation have been pursued. mPGES-1 is a promising target because its inhibition would not cause the side-effects related to COX inhibition. To identify novel inhibitors of mPGES-1, we developed a ligand-based pharmacophore model that differentiates true inhibitors from decoys and enlightens the structure-activity relationships for known mPGES-1 inhibitors. The model (four hydrophobic centers, two hydrogen bond acceptor and two hydrogen bond donor points) was employed to select lead-like compounds from ZINC database for in vivo evaluation. Among the 18 compounds selected, five inhibited the fever induced by LPS. The most potent compound (5-(4-fluorophenyl)-3-({6-methylimidazo[1,2-a]pyridin-2-yl}methyl)-2,3dihydro-1,3,4-oxadiazol-2-one) is active peripherally (i.v.) or centrally (i.c.v.) (82.18% and 112% reduction, respectively) and reduces (69.13%) hypothalamic PGE₂ production, without significant COX-1/2 inhibition. In conclusion, our in silico approach leads to the selection of a compound that presents the chemical features to inhibit mPGES-1 and reduces fever induced by LPS. Furthermore, the in vivo and in vitro results support the hypothesis that its mechanism of action does not depend on COX inhibition. Hence, it can be considered a promising lead compound for antipyretic development, once it would not have the side-effects of COX-1/2 inhibitors.

Can Direct Current Electrotherapy Be Used for Patients With Orthopedic Implants?

Introduction:

Although electrotherapy appears to have particularly interesting applications in the field of postoperative orthopedic rehabilitation, relatively little scientifically based research has been conducted in the area of electrotherapy with regard to safety involving patients with orthopedic implants.

Method:

Three electrotherapy forms were tested, such as high-volt stimulation (HVS), transcutaneous electric nerve stimulation (TENS), and galvanic current (GAL), using a model system containing a metal implant plate to evaluate whether heating in excess of 3°C would occur.

Results:

All changes in temperature for HVS, GAL, and TENS therapeutic electrical currents observed in our model system fall below the predefined 3°C.

Conclusion:

To the best of our knowledge, this is the first experimental based observation that prolonged exposure to a direct electrical current at therapeutic strength does not result in heating of metal titanium plates.

Cytolethal distending toxin-producing Escherichia coli strains causing severe diarrhoea in young Mexican children

Introduction. Cytolethal distending toxins (CDTs), encoded by cdt genes, have DNase activity leading to cellular and nuclear distension, resulting in irreversible cell cycle arrest and apoptosis of target cells. cdt-positive Escherichia coli strains have been isolated from children with diarrhoea. There is, however, scant information on the prevalence and clinical presentation of diarrhoeal disease caused by these strains. Furthermore, toxin production of cdt-positive strains is rarely confirmed. We report five young children with diarrhoea caused by CDT-producing E. coli in whom stools were negative for other bacterial or enteric pathogens.

Case presentation. On admission to hospital, all children presented watery diarrhoea with high stool output (range 7–20 stools/24 h); five had fever of 38 °C or more and four presented vomiting. Dehydration was present in four patients, one of whom had hypovolaemic shock; one child also presented hyponatraemia and hypokalaemia. In two children, cdt-positive strains were classified as typical and atypical enteropathogenic E. coli, and the remaining three harboured cdt-positive strains that did not belong to any diarrhoeagenic pathogroup. One cdt-positive strain from each case was characterized by a CDT cytotoxic assay and a cdt type-specific PCR. All strains produced the characteristic cellular intoxication due to CDT. Two strains carried the cdt-I, one cdt-III, one cdt-IV, and one concurrently had cdt-I, cdt-II and cdt-III genes.

Conclusion. Our results suggest that CDT-producing E. coli strains are an infrequent, albeit significant, cause of severe diarrhoeal illness in children. Future research should measure the true burden of cdt-positive E. coli diarrhoea among children.

Paracetamol in fever in critically ill patients-an update

Fever, which is arbitrary defined as an increase in body temperature above 38.3°C, can affect up to 90% of patients admitted in intensive care unit. Induction of fever is mediated by the release of pyrogenic cytokines (tumor necrosis factor α, interleukin 1, interleukin 6, and interferons). Fever is associated with increased length of stay in intensive care unit and with a worse outcome in some subgroups of patients (mainly neurocritically ill patients). Although fever can increase oxygen consumption in unstable patients, on the contrary, it can activate physiologic systems that are involved in pathogens clearance. Treatments to reduce fever include the use of antipyretics. Thus, the reduction of fever might reduce the ability to develop an efficient host response. This balance, between harms and benefits, has to be taken into account every time we decide to treat or not to treat fever in a given patient. Among the antipyretics, paracetamol is one of the most common used. Paracetamol is a synthetic, nonopioid, centrally acting analgesic, and antipyretic drug. Its antipyretic effect occurs because it inhibits cyclooxygenase-3 and the prostaglandin synthesis, within the central nervous system, resetting the hypothalamic heat-regulation center. In this clinical review, we will summarize the use of paracetamol as antipyretic in critically ill patients (sepsis, trauma, neurological, and medical).