The differential role of prostaglandin E2 receptors EP3 and EP4 in regulation of fever

Sublingual Misoprostol-Induced Rhabdomyolysis and Convulsions in Postpartum Hemorrhage: A Case Report and Literature Review

Postpartum hemorrhage (PPH) remains the leading cause of maternal mortality, primarily attributed to uterine atony. Both the World Health Organization (WHO) and the International Federation of Gynecology and Obstetrics (FIGO) endorse the use of misoprostol not only for the prevention but also for the treatment of PPH. However, the administration of misoprostol is commonly associated with transient pyrexia, attributed to a shift in the hypothalamic set point observed in certain animal studies. Misoprostol-induced hyperpyrexia can occasionally manifest with a prodrome of shivering, particularly when administered via the sublingual route, which achieves a higher and faster maximum plasma concentration compared to vaginal and rectal routes. General management strategies to reduce fever involve removing clothing and blankets, applying cool compresses, administering oral acetaminophen, and ensuring adequate hydration. While some cases have reported misoprostol-induced convulsions, hyperpyrexia leading to convulsions and subsequent rhabdomyolysis is a rare and potentially lethal side effect. In this case presentation, we emphasize a scenario where misoprostol was employed for the treatment of PPH but led to rhabdomyolysis. Our goal is to highlight the side effects of misoprostol and the significance of considering the initial combination of misoprostol with anti-pyretic management to minimize the risk of hyperthermia-related side effects and prevent additional severe complications.

L-Citrulline Influences the Body Temperature, Heat Shock Response and Nitric Oxide Regeneration of Broilers Under Thermoneutral and Heat Stress Condition

Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Pathophysiology of Fever and Application of Infrared Thermography (IRT) in the Detection of Sick Domestic Animals: Recent Advances

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

Cross-effect of TRPV1 and EP3 receptor on coughs and bronchopulmonary C-neural activities

Prostaglandin E₂ (PGE₂)-induced coughs in vivo and vagal nerve depolarization in vitro are inhibited by systemic and local administration of prostaglandin EP3 receptor (L-798106) and TRPV1 antagonists (JNJ 17203212). These results indicate a modulating effect of TRPV1 on the EP3 receptor-mediated cough responses to PGE₂ likely through the vagal sensory nerve. This study aimed to determine whether 1) inhalation of aerosolized JNJ 17203212 and L-798106 affected cough responses to citric acid (CA, mainly stimulating TRPV1) and PGE₂; 2) TRPV1 and EP3 receptor morphologically are co-expressed and electrophysiologically functioned in the individual of vagal pulmonary C-neurons (cell bodies of bronchopulmonary C-fibers in the nodose/jugular ganglia); and 3) there was a cross-effect of TRPV1 and EP3 receptor on these neural excitations. To this end, aerosolized CA or PGE₂ was inhaled by unanesthetized guinea pigs pretreated without or with each antagonist given in aerosol form. Immunofluorescence was applied to identify the co-expression of TRPV1 and EP3 receptor in vagal pulmonary C-neurons (retrogradely traced by DiI). Whole-cell voltage patch clamp approach was used to detect capsaicin (CAP)- and PGE₂-induced currents in individual vagal pulmonary C-neurons and determine the effects of the TRPV1 and EP3 receptor antagonists on the evoked currents. We found that PGE₂-induced cough was attenuated by JNJ 17203212 or L-798106 and CA-evoked cough greatly suppressed only by JNJ 17203212. Approximately 1/4 of vagal pulmonary C-neurons co-expressed EP3 with a cell size < 20 μm. Both CAP- and PGE₂-induced currents could be recorded in the individuals of some vagal pulmonary C-neurons. The former was largely inhibited only by JNJ 17203212, while the latter was suppressed by JNJ 17203212 or L-798106. The similarity of the cross-effect of both antagonists on cough and vagal pulmonary C-neural activity suggests that a subgroup of vagal pulmonary C-neurons co-expressing TRPV1 and EP3 receptor is, at least in part, responsible for the cough response to PGE₂.

Microbial metabolite deoxycholic acid controls Clostridium perfringens-induced chicken necrotic enteritis through attenuating inflammatory cyclooxygenase signaling

Necrotic enteritis (NE) caused by Clostridium perfringens infection has reemerged as a prevalent poultry disease worldwide due to reduced usage of prophylactic antibiotics under consumer preferences and regulatory pressures. The lack of alternative antimicrobial strategies to control this disease is mainly due to limited insight into the relationship between NE pathogenesis, microbiome, and host responses. Here we showed that the microbial metabolic byproduct of secondary bile acid deoxycholic acid (DCA), at as low as 50 µM, inhibited 82.8% of C. perfringens growth in Tryptic Soy Broth (P < 0.05). Sequential Eimeria maxima and C. perfringens challenges significantly induced NE, severe intestinal inflammation, and body weight (BW) loss in broiler chickens. These negative effects were diminished (P < 0.05) by 1.5 g/kg DCA diet. At the cellular level, DCA alleviated NE-associated ileal epithelial death and significantly reduced lamina propria cell apoptosis. Interestingly, DCA reduced C. perfringens invasion into ileum (P < 0.05) without altering the bacterial ileal luminal colonization. Molecular analysis showed that DCA significantly reduced inflammatory mediators of Infγ, Litaf, Il1β, and Mmp9 mRNA accumulation in ileal tissue. Mechanism studies revealed that C. perfringens induced (P < 0.05) elevated expression of inflammatory mediators of Infγ, Litaf, and Ptgs2 (Cyclooxygenases-2 (COX-2) gene) in chicken splenocytes. Inhibiting the COX signaling by aspirin significantly attenuated INFγ-induced inflammatory response in the splenocytes. Consistent with the in vitro assay, chickens fed 0.12 g/kg aspirin diet protected the birds against NE-induced BW loss, ileal inflammation, and intestinal cell apoptosis. In conclusion, microbial metabolic product DCA prevents NE-induced BW loss and ileal inflammation through attenuating inflammatory response. These novel findings of microbiome protecting birds against NE provide new options on developing next generation antimicrobial alternatives against NE.

Pyrogens, a polypeptide produces fever by metabolic changes in hypothalamus: Mechanisms and detections

Fever is one of the cardinal symptoms of onset of an infection or inflammation and is the common clinical indicator for medical consultation in mammalian host worldwide. Simply, fever manifested with elevation of body temperature from normal physiological range represents adaptive response of immune system on challenge with an infectious and non-infectious circumstance. Fever usually initiated in the periphery as a result of interaction of immune cells with exogenous or endogenous pyrogens. Peripheral pyrogenic signals gain access to the central nervous system via humoral and neural route. Humoral pathway was initiated with production of pyrogenic cytokines and prostaglandins from immune cells of blood as well as liver, transmitted directly to pre-optic area of hypothalamus through the circumventricular organ of brain. On the other hand an alternative pathway was initiated by the same cytokines indirectly via stimulating the vagal sensory neurons result in pyrogenic fever; so-called neuronal pathway. If the magnitude of pyrogens associated fever is very high, it will lead to severe illness ranging from septic shock to death. So it is necessary to evaluate the presence of pyrogens in implants, medical devices, drugs and biological materials to ensure safety in biomedical applications and therapeutics. Classification, route of administration, mechanism of action and detection of pyrogens and associated products are the major subject of this review.

Profiling changes in cortical astroglial cells following chronic stress

Recent studies have suggested that cortical astroglia play an important role in depressive-like behaviors. Potential astroglial contributions have been proposed based on their known neuroplastic functions, such as glutamate recycling and synaptic plasticity. However, the specific mechanisms by which astroglial cells may contribute or protect against a depressive phenotype remain unknown. To delineate astroglial changes that accompany depressive-like behavior, we used astroglial-specific bacTRAP mice exposed to chronic variable stress (CVS) and profiled the astroglial translatome using translating ribosome affinity purification (TRAP) in conjunction with RNAseq. As expected, CVS significantly increased anxiety- and depressive-like behaviors and corticosterone levels and decreased GFAP expression in astroglia, although this did not reflect a change in the total number of astroglial cells. TRAPseq results showed that CVS decreased genes associated with astroglial plasticity: RhoGTPases, growth factor signaling, and transcription regulation, and increased genes associated with the formation of extracellular matrices such as perineuronal nets (PNNs). PNNs inhibit neuroplasticity and astroglia contribute to the formation, organization, and maintenance of PNNs. To validate our TRAPseq findings, we showed an increase in PNNs following CVS. Degradation of PNNs in the prefrontal cortex of mice exposed to CVS reversed the CVS-induced behavioral phenotype in the forced swim test. These data lend further support to the neuroplasticity hypothesis of depressive behaviors and, in particular, extend this hypothesis beyond neuronal plasticity to include an overall decrease in genes associated with cortical astroglial plasticity following CVS. Further studies will be needed to assess the antidepressant potential of directly targeting astroglial cell function in models of depression.

Effects of prostaglandin E2 on cells cultured from the rat organum vasculosum laminae terminalis and median preoptic nucleus

The time course of the induction of enzymes responsible for the formation of prostaglandin E2 (PGE2) after an inflammatory insult, in relation to the concomitant febrile response, suggests that peripherally generated PGE2 is involved in the induction of the early phase of fever, while centrally produced PGE2 exerts pyrogenic capacities during the later stages of fever within the hypothalamic median preoptic nucleus (MnPO). The actions of peripherally derived PGE2 on the brain might occur at the level of the organum vasculosum laminae terminalis (OVLT), which lacks a tight blood-brain barrier and is implicated in fever, while the effects of PGE2 within the MnPO might interfere with glutamatergic neurotransmission within a recently characterized central efferent pathway for the activation of cold-defence reactions. Using the fura-2 ratio imaging technique we, therefore, measured changes of the intracellular Ca(2+)-concentration in primary neuroglial microcultures of rat OVLT and MnPO stimulated with PGE2 and/or glutamate. In cultures from the OVLT, as opposed to those derived from the MnPO, substantial numbers of neurons (8% of 385), astrocytes (19% of 645) and microglial cells (28% of 43) directly responded to PGE2 with a transient increase of intracellular Ca(2+). The most pronounced effect of PGE2 on cells from MnPO microcultures was its modulatory influence on the strength of glutamate-induced Ca(2+)-signals. In 72 out of 512 neurons and in 105 out of 715 astrocytes PGE2 significantly augmented glutamate-induced Ca(2+)-signals. About 30% of these neurons were GABAergic. These observations are in agreement with putative roles of peripheral PGE2 as a directly acting circulating agent at the level of the OVLT, and of central MnPO-intrinsic PGE2 as an enhancer of glutamatergic neurotransmission, which causes disinhibition of thermogenic heat production, a crucial component for the manifestation of fever. In microcultures from both brain sites investigated incubation with PGE2 significantly reduced the lipopolysaccharide-induced release of cytokines (tumor necrosis factor-α and interleukin-6) into the supernatant. PGE2, thus, seems to be involved in a negative feed-back loop to limit the strength of the brain inflammatory process and to play a dual role with pro- as well as anti-inflammatory properties.

Misoprostol-induced fever and genetic polymorphisms in drug transporters SLCO1B1 and ABCC4 in women of Latin American and European ancestry

AIM

Misoprostol, a prostaglandin analogue used for the treatment of postpartum hemorrhage and termination of pregnancy, can cause high fevers. Genetic susceptibility may play a role in misoprostol-induced fever.

SUBJECTS & METHODS

Body temperature of women treated with misoprostol for termination of pregnancy in the UK (n = 107) and for postpartum hemorrhage in Ecuador (n = 50) was measured. Genotyping for 33 single nucleotide polymorphisms in 15 candidate genes was performed. Additionally, we investigated the transport of radiolabeled misoprostol acid across biological membranes in vitro.

RESULTS

The ABCC4 single nucleotide polymorphism rs11568658 was associated with misoprostol-induced fever. Misoprostol acid was transported across a blood-brain barrier model by MRP4 and SLCO1B1.

CONCLUSION

Genetic variability in ABCC4 may contribute to misoprostol-induced fever in pregnant women. Original submitted 21 January 2015; Revision submitted 24 April 2015.

Cytokines: how important are they in mediating sickness?

Sickness refers to a set of coordinated physiological and behavioral changes in response to systemic inflammation. It is characterized by fever, malaise, social withdrawal, fatigue, and anorexia. While these responses collectively represent a protective mechanism against infection and injury, increasing lines of evidence indicate that over-exaggerated or persistent sickness can damage the brain, and could possibly raise the risk to developing delirium. Therefore, a clear understanding in sickness will be beneficial. It has long been believed that sickness results from increased systemic cytokines occurring during systemic inflammation. However, in recent years more and more conflicting data have suggested that development of sickness following peripheral immune challenge could be independent of cytokines. Hence, it is confusing as to whether cytokines really do act as primary mediators of sickness, or if they are secondary to alternative inducing factor(s). In this review, we will (1) introduce the relationships between systemic inflammation, cytokines, sickness, and delirium, and (2) attempt to interpret the recent controversies.

Central control of thermogenesis

In mammals and birds, conservation of body heat at around 37 °C is vital to life. Thermogenesis is the production of this heat which can be obligatory, as in basal metabolic rate, or it can be facultative such as the response to cold. A complex regulatory system has evolved which senses environmental or core temperature and integrates this information in hypothalamic regions such as the preoptic area and dorsomedial hypothalamus. These areas then send the appropriate signals to generate and conserve heat (or dissipate it). In this review, the importance of the sympathetic nervous system is discussed in relation to its role in basal metabolic rate and adaptive thermogenesis with a particular emphasis to human obesity. The efferent sympathetic pathway does not uniformly act on all tissues; different tissues can receive different levels of sympathetic drive at the same time. This is an important concept in the discussion of the pharmacotherapy of obesity. Despite decades of work the medicine chest contains only one pill for the long term treatment of obesity, orlistat, a lipase inhibitor that prevents the absorption of lipid from the gut and is itself not systemically absorbed. The central controlling system for thermogenesis has many potential intervention points. Several drugs, previously marketed, awaiting approval or in the earlier stages of development may have a thermogenic effect via activation of the sympathetic nervous system at some point in the thermoregulatory circuit and are discussed in this review. If the balance is weighted to the "wrong" side there is the burden of increased cardiovascular risk while a shift to the "right" side, if possible, will afford a thermogenic benefit that is conducive to weight loss maintenance. This article is part of a Special Issue entitled 'Central Control Food Intake'

EP₃ receptors mediate PGE₂-induced hypothalamic paraventricular nucleus excitation and sympathetic activation

Prostaglandin E(2) (PGE(2)), an important mediator of the inflammatory response, acts centrally to elicit sympathetic excitation. PGE(2) acts on at least four E-class prostanoid (EP) receptors known as EP(1), EP(2), EP(3), and EP(4). Since PGE(2) production within the brain is ubiquitous, the different functions of PGE(2) depend on the expression of these prostanoid receptors in specific brain areas. The type(s) and location(s) of the EP receptors that mediate sympathetic responses to central PGE(2) remain unknown. We examined this question using PGE(2), the relatively selective EP receptor agonists misoprostol and sulprostone, and the available selective antagonists for EP(1), EP(3), and EP(4). In urethane-anesthetized rats, intracerebroventricular (ICV) administration of PGE(2), sulprostone or misoprostol increased renal sympathetic nerve activity, blood pressure, and heart rate. These responses were significantly reduced by ICV pretreatment with the EP(3) receptor antagonist; the EP(1) and EP(4) receptor antagonists had little or no effect. ICV PGE(2) or misoprostol increased the discharge of neurons in the hypothalamic paraventricular nucleus (PVN). ICV misoprostol increased the c-Fos immunoreactivity of PVN neurons, an effect that was substantially reduced by the EP(3) receptor antagonist. Real-time PCR detected EP(3) receptor mRNA in PVN, and immunohistochemical studies revealed sparsely distributed EP(3) receptors localized in GABAergic terminals and on a few PVN neurons. Direct bilateral PVN microinjections of PGE(2) or sulprostone elicited sympathoexcitatory responses that were significantly reduced by the EP(3) receptor antagonist. These data suggest that EP(3) receptors mediate the central excitatory effects of PGE(2) on PVN neurons and sympathetic discharge.

Pulse exposure of haematopoietic grafts to prostaglandin E2 in vitro facilitates engraftment and recovery

OBJECTIVES

The aim of this study was to evaluate the effects of prostaglandin E(2) (PGE(2) ) on haematopoietic stem cell (HSC) function and determine its mechanism of action.

MATERIALS AND METHODS

HSC were exposed to PGE(2) for 2 h and effects on their homing, engraftment and self-renewal evaluated in vivo. Effects of PGE(2) on HSC cell cycle, CXCR4 expression and migration to SDF-1α were analysed in vitro. Apoptosis was evaluated by examination of survivin expression and active caspase-3 levels.

RESULTS

Equivalent haematopoietic reconstitution was demonstrated using 4-fold fewer PGE(2) -treated cells compared to controls. Multilineage reconstitution was stable on secondary transplantation, indicating that PGE(2) affects long-term repopulating HSC (LT-HSC) and that enhanced chimaerism of PGE(2) -pulsed cells results from their initial treatment. PGE(2) increased CXCR4 expression on mouse and human HSC, increased their migration to SDF-1αin vitro and enhanced in vivo marrow homing 2-fold, which was blocked by a CXCR4 receptor antagonist. PGE(2) pulse exposure reduced apoptosis of mouse and human HSC, with increase in endogenous caspase inhibitor survivin, and concomitant decrease in active caspase-3. Two-fold more HSC entered the cell cycle and proliferated within 24 h after PGE(2) pulse exposure.

CONCLUSIONS

These studies demonstrate that short-term PGE(2) exposure enhances HSC function and supports the concept of utility of PGE(2) as an ex vivo strategy to improve function of haematopoietic grafts, particularly those where HSC numbers are limited.

The neurobiology of lipid metabolism in autism spectrum disorders

Autism is a neurodevelopmental disorder characterized by impairments in communication and reciprocal social interaction, coupled with repetitive behavior, which typically manifests by 3 years of age. Multiple genes and early exposure to environmental factors are the etiological determinants of the disorder that contribute to variable expression of autism-related traits. Increasing evidence indicates that altered fatty acid metabolic pathways may affect proper function of the nervous system and contribute to autism spectrum disorders. This review provides an overview of the reported abnormalities associated with the synthesis of membrane fatty acids in individuals with autism as a result of insufficient dietary supplementation or genetic defects. Moreover, we discuss deficits associated with the release of arachidonic acid from the membrane phospholipids and its subsequent metabolism to bioactive prostaglandins via phospholipase A(2)-cyclooxygenase biosynthetic pathway in autism spectrum disorders. The existing evidence for the involvement of lipid neurobiology in the pathology of neurodevelopmental disorders such as autism is compelling and opens up an interesting possibility for further investigation of this metabolic pathway.

Eicosanoid regulation of hematopoiesis and hematopoietic stem and progenitor trafficking

Hematopoietic stem cell (HSC) transplantation is a potentially curative treatment for numerous hematological malignancies. The transplant procedure as performed today takes advantage of HSC trafficking; either egress of HSC from the bone marrow to the peripheral blood, that is, mobilization, for acquisition of the hematopoietic graft, and/or trafficking of HSC from the peripheral blood to bone marrow niches in the recipient patient, that is HSC homing. Numerous studies, many of which are reviewed herein, have defined hematopoietic regulatory mechanisms mediated by the 20-carbon lipid family of eicosanoids, and recent evidence strongly supports a role for eicosanoids in regulation of hematopoietic trafficking, adding a new role whereby eicosanoids regulate hematopoiesis. Short-term exposure of HSC to the eicosanoid prostaglandin E(2) increases CXCR4 receptor expression, migration and in vivo homing of HSC. In contrast, cannabinoids reduce hematopoietic progenitor cell (HPC) CXCR4 expression and induce HPC mobilization when administered in vivo. Leukotrienes have been shown to alter CD34(+) cell adhesion, migration and regulate HSC proliferation, suggesting that eicosanoids have both opposing and complimentary roles in the regulation of hematopoiesis. As numerous FDA approved compounds regulate eicosanoid signaling or biosynthesis, the utility of eicosanoid-based therapeutic strategies to improve hematopoietic transplantation can be rapidly evaluated.

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.

Parallel preoptic pathways for thermoregulation

Sympathetic premotor neurons in the rostral medullary raphe (RMR) regulate heat conservation by tail artery vasoconstriction and brown adipose tissue thermogenesis. These neurons are a critical relay in the pathway that increases body temperature. However, the origins of the inputs that activate the RMR during cold exposure have not been definitively identified. We investigated the afferents to the RMR that were activated during cold by examining Fos expression in retrogradely labeled neurons after injection of cholera toxin B subunit (CTb) in the RMR. These experiments identified a cluster of Fos-positive neurons in the dorsomedial hypothalamic nucleus and dorsal hypothalamic area (DMH/DHA) with projections to the RMR that may mediate cold-induced elevation of body temperature. Also, neurons in the median preoptic nucleus (MnPO) and dorsolateral preoptic area (DLPO) and in the A7 noradrenergic cell group were retrogradely labeled but lacked Fos expression, suggesting that they may inhibit the RMR. To investigate whether individual or common preoptic neurons project to the RMR and DMH/DHA, we injected CTb into the RMR and Fluorogold into the DMH/DHA. We found that projections from the DLPO and MnPO to the RMR and DMH/DHA emerge from largely separate neuronal populations, indicating they may be differentially regulated. Combined cell-specific lesions of MnPO and DLPO, but not lesions of either one alone, caused baseline hyperthermia. Our data suggest that the MnPO and DLPO provide parallel inhibitory pathways that tonically inhibit the DMH/DHA and the RMR at baseline, and that hyperthermia requires the release of this inhibition from both nuclei.

Roles of two preoptic cell groups in tonic and febrile control of rat tail sympathetic fibers

In response to cold and in fever, heat dissipation from the skin is reduced by sympathetic vasoconstriction. The preoptic region has been implicated in regulating basal, thermal, and febrile vasoconstriction of cutaneous vessels such as the rat's tail, but the neurons responsible for these functions have not been well localized. We recorded activity from single sympathetic nerve fibers supplying tail vessels in urethane-anesthetized rats, while microinjections of GABA (300 mM, 15–30 nl) were used to inhibit neurons in different parts of the preoptic region. Tail fiber activity increased promptly after GABA injections in two distinct regions: a rostromedial preoptic region (RMPO) centered around the organum vasculosum of the lamina terminalis, and a second region centered ∼1 mm caudolaterally (CLPO). Responses to GABA within each region were similar. The febrile mediator, PGE2 (0.2 or 1 ng in 15 nl) was then microinjected into GABA-sensitive preoptic sites. Injections of PGE2 into the RMPO induced a rapid increase in tail fiber activity followed by a rise in core temperature; injections into the rostromedial part of CLPO gave delayed tail fiber responses; injections into the central and caudal parts of CLPO were without effect. These results indicate that neurons in two distinct preoptic regions provide tonic inhibitory drive to the tail vasoconstrictor supply, but febrile vasoconstriction is mediated by PGE2 selectively inhibiting neurons in the rostromedial region.

Current concepts regarding the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating disease that predominantly affects premature neonates. The mortality associated with NEC has not changed appreciably over the past several decades. The underlying etiology of NEC remains elusive, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by massive epithelial destruction, which results in gut barrier failure. The exact molecular and cellular mechanisms involved in this complex disease are poorly understood. Recent studies have provided significant insight into our understanding of the pathogenesis of NEC. Endogenous mediators such as prostanoids, cyclooxygenases, and nitric oxide may play a role in the development of gut barrier failure. Understanding the structural architecture of the gut barrier and the cellular mechanisms that are responsible for gut epithelial damage could lead to the development of novel diagnostic, prophylactic and therapeutic strategies in NEC.

Prostaglandin involvement in hyperthermia induced by sleep deprivation: a pharmacological and autoradiographic study

AIMS

Hyperthermia is a characteristic functional effect of sleep deprivation (SD). We hypothesize here that prostaglandin E2 (PGE2) could be involved in hyperthermia induced by sleep deprivation.

MAIN METHODS

To address this issue we examined the effects of a selective cyclo-oxygenase-2 inhibitor (COX-2) agent on hyperthermia induced by SD in rats. We also investigated binding to PGE2 receptors in hypothalamic brain areas of sleep-deprived rats using in vitro autoradiography. Male Wistar rats were deprived of sleep for 96 h using the platform technique. Sleep deprived and control groups received saline or Celecoxib (20, 30 and 40 mg/kg; p.o.) daily during the SD period. Colonic temperature was measured daily.

KEY FINDINGS

Results indicated that core temperature of sleep-deprived rats that receiving saline increased from the first to the fourth day of SD compared to baseline and to the respective control group. However, the hyperthermia induced by SD was not blocked by COX-2 inhibitor at any dose. [(3)H]PGE2 binding did not differ significantly among the groups in any of a number of hypothalamic areas examined.

SIGNIFICANCE

Although SD rats showed no response to the COX-2 inhibitor and no alterations in [(3)H]PGE2 binding, the possibility remains that other prostaglandin system and/or receptor subtypes may be altered by SD.

Development of a novel noncompetitive antagonist of IL-1 receptor

IL-1 is a major proinflammatory cytokine which interacts with the IL-1 receptor I (IL-1RI) complex, composed of IL-1RI and IL-1R accessory protein subunits. Currently available strategies to counter pathological IL-1 signaling rely on a recombinant IL-1 receptor antagonist, which directly competes with IL-1 for its binding site. Presently, there are no small antagonists of the IL-1RI complex. Given this void, we derived 15 peptides from loops of IL-1R accessory protein, which are putative interactive sites with the IL-1RI subunit. In this study, we substantiate the merits of one of these peptides, rytvela (we termed "101.10"), as an inhibitor of IL-1R and describe its properties consistent with those of an allosteric negative modulator. 101.10 (IC(50) approximately 1 nM) blocked human thymocyte proliferation in vitro, and demonstrated robust in vivo effects in models of hyperthermia and inflammatory bowel disease as well as topically in contact dermatitis, superior to corticosteroids and IL-1ra; 101.10 did not bind to IL-1RI deficient cells and was ineffective in vivo in IL-1RI knockout mice. Importantly, characterization of 101.10, revealed noncompetitive antagonist actions and functional selectivity by blocking certain IL-1R pathways while not affecting others. Findings describe the discovery of a potent and specific small (peptide) antagonist of IL-1RI, with properties in line with an allosteric negative modulator.

Central and peripheral neuroimmune responses: hyporesponsiveness during pregnancy

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

Molecular signaling in necrotizing enterocolitis: regulation of intestinal COX-2 expression

Necrotizing enterocolitis (NEC) is the most common surgical emergency in premature infants. The underlying etiology of NEC remains unknown, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by exuberant gut inflammation leading to ischemia and coagulation necrosis of the intestinal epithelium. The molecular and cellular mechanisms responsible for these pathologic changes are poorly understood. It has been shown that various exogenous and endogenous mediators such as lipopolysaccharide, inflammatory cytokines, platelet activating factor, and nitric oxide may play a role in the pathogenesis of NEC. Recent studies in our laboratory and others have established a link between NEC and activation of cyclooxygenase-2, the enzyme that catalyzes the rate-limiting step in the biosynthesis of prostanoids. The challenge is in defining the molecular signaling pathways leading to accumulation of these mediators early in the disease progression, before the onset of tissue necrosis and systemic sepsis. Identification and characterization of these pathways could lead to the development of novel treatment strategies to alleviate the morbidity and mortality associated with NEC.

Arachidonic acid metabolism in brain physiology and pathology: lessons from genetically altered mouse models

The arachidonic acid (AA) cascade involves the release of AA from the membrane phospholipids by a phospholipase A(2), followed by its subsequent metabolism to bioactive prostanoids by cyclooxygenases coupled with terminal synthases. Altered brain AA metabolism has been implicated in neurological, neurodegenerative, and psychiatric disorders. The development of genetically altered mice lacking specific enzymes of the AA cascade has helped to elucidate the individual roles of these enzymes in brain physiology and pathology. The roles of AA and its metabolites in brain physiology, with a particular emphasis on the phospholipase A(2)/cyclooxygenases pathway, are summarized, and the specific phenotypes of genetically altered mice relevant to brain physiology and neurotoxic models are discussed.

Night eating and obesity in the EP3R-deficient mouse

Adult mice carrying a null mutation of the prostanoid receptor EP3R (EP3R(-/-) mice) exhibit increased frequency of feeding during the light cycle of the day and develop an obese phenotype under a normal fat diet fed ad libitum. EP3R(-/-) mice show increased motor activity, which is not sufficient to offset the increased feeding leading to increased body weight. Altered "nocturnal" activity and feeding behavior is present from a very early age and does not seem to require age-dependent factors for the development of obesity. Obesity in EP3R(-/-) mice is characterized by elevated leptin and insulin levels and >20% higher body weight compared with WT littermates. Abdominal and subcutaneous fat and increased liver weight account for the weight increase in EP3R(-/-) mice. These observations expand the roles of prostaglandin E(2) signaling in metabolic regulation beyond the reported stimulation of leptin release from adipose tissue to involve actions mediated by EP3R in the regulation of sleep architecture and feeding behavior. The findings add to the growing literature on links between inflammatory signaling and obesity.

Circulating interleukin-6 induces fever through a STAT3-linked activation of COX-2 in the brain

Interleukin (IL)-6 is an important humoral mediator of fever following infection and inflammation and satisfies a number of criteria for a circulating pyrogen. However, evidence supporting such a role is diminished by the moderate or even absent ability of the recombinant protein to induce fever and activate the cyclooxygenase-2 (COX-2) pathway in the brain, a prerequisite step in the initiation and maintenance of fever. In the present study, we investigated the role of endogenous circulating IL-6 in a rodent model of localized inflammation, by neutralizing its action using a specific antiserum (IL-6AS). Rats were injected with LPS (100 microg/kg) or saline into a preformed air pouch in combination with an intraperitoneal injection of either normal sheep serum or IL-6AS (1.8 ml/rat). LPS induced a febrile response, which was accompanied by a significant rise in plasma IL-6 and nuclear STAT3 translocation in endothelial cells throughout the brain 2 h after treatment, including areas surrounding the sensory circumventricular organs and the median preoptic area (MnPO), important regions in mediating fever. These responses were abolished in the presence of the IL-6AS, which also significantly inhibited the LPS-induced upregulation of mRNA expression or immunoreactivity (IR) of the inducible form of COX, the rate-limiting enzyme for PGE2-synthesis. Interestingly, nuclear signal transducer and activator of transcription (STAT)3-positive cells colocalized with COX-2-IR, signifying that IL-6-activated cells are directly involved in PGE2 production. These observations suggest that IL-6 is an important circulating pyrogen that activates the COX-2-pathway in cerebral microvasculature, most likely through a STAT3-dependent pathway.