Karin Rudolph

An antipyretic role for interleukin-10 in LPS fever in mice

Interleukin (IL)-10 inhibits the synthesis of proinflammatory cytokines implicated in fever, including IL-1β, IL-6, and tumor necrosis factor (TNF)-α. We hypothesized that IL-10 functions as an antipyretic in the regulation of fevers to lipopolysaccharide (LPS) and turpentine. Body temperature was measured by biotelemetry. Swiss Webster (SW) mice treated with recombinant murine IL-10 were resistant to fever induced by a low dose of LPS (100 μg/kg ip) and to the hypothermic and febrile effects of a high (septiclike) dose of LPS (2.5 mg/kg ip). IL-10 knockout mice developed an exacerbated and prolonged fever in response to a low dose of LPS (50 μg/kg ip) compared with their wild-type counterparts. At 4 h after injection of the low dose of LPS, plasma levels of IL-6, but not TNF-α, were significantly elevated in the IL-10 knockout mice compared with their wild-type controls (ANOVA, P < 0.05). After injection of the same high dose of LPS injected into SW mice, wild-type mice developed a fever at 24 h whereas IL-10 knockout mice immediately developed a profound hypothermia that lasted through 41 h (ANOVA, P < 0.05). Body weight and food intake were more significantly depressed in response to the high dose of LPS in the knockout mice compared with their wild-type controls. Only 30% of the IL-10 knockout mice survived compared with 100% of the wild-type mice (Fishers exact test, P < 0.05). Fever in response to the injection of turpentine (100 μl/mouse sc) did not differ between wild-type and IL-10 knockout mice. These data support the hypotheses that 1) IL-10 functions as an endogenous antipyretic following exposure to LPS, 2) a putative mechanism of the early antipyretic action of IL-10 is through the inhibition of plasma levels of IL-6, 3) IL-10 has a protective role in the lethal effects of exposure to high levels of LPS, and 4) endogenous IL-10 does not have a role in fever induced by turpentine.Interleukin (IL)-10 inhibits the synthesis of proinflammatory cytokines implicated in fever, including IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. We hypothesized that IL-10 functions as an antipyretic in the regulation of fevers to lipopolysaccharide (LPS) and turpentine. Body temperature was measured by biotelemetry. Swiss Webster (SW) mice treated with recombinant murine IL-10 were resistant to fever induced by a low dose of LPS (100 microgram/kg ip) and to the hypothermic and febrile effects of a high (septiclike) dose of LPS (2.5 mg/kg ip). IL-10 knockout mice developed an exacerbated and prolonged fever in response to a low dose of LPS (50 microgram/kg ip) compared with their wild-type counterparts. At 4 h after injection of the low dose of LPS, plasma levels of IL-6, but not TNF-alpha, were significantly elevated in the IL-10 knockout mice compared with their wild-type controls (ANOVA, P < 0.05). After injection of the same high dose of LPS injected into SW mice, wild-type mice developed a fever at 24 h whereas IL-10 knockout mice immediately developed a profound hypothermia that lasted through 41 h (ANOVA, P < 0.05). Body weight and food intake were more significantly depressed in response to the high dose of LPS in the knockout mice compared with their wild-type controls. Only 30% of the IL-10 knockout mice survived compared with 100% of the wild-type mice (Fishers exact test, P < 0.05). Fever in response to the injection of turpentine (100 microliter/mouse sc) did not differ between wild-type and IL-10 knockout mice. These data support the hypotheses that 1) IL-10 functions as an endogenous antipyretic following exposure to LPS, 2) a putative mechanism of the early antipyretic action of IL-10 is through the inhibition of plasma levels of IL-6, 3) IL-10 has a protective role in the lethal effects of exposure to high levels of LPS, and 4) endogenous IL-10 does not have a role in fever induced by turpentine.

Inhibitors of alternative pathways of arachidonate metabolism differentially affect fever in mice

Inhibitors of cyclooxygenases prevent fever. The purpose of this study was to test the hypothesis that selective and dual inhibitors of the other enzyme systems of arachidonic acid oxygenation (i.e., lipoxygenase and epoxygenase) affect the time course or magnitude of fever in mice. Swiss Webster mice kept at 30 degreesC ambient temperature were implanted with biotelemeters to monitor body temperature. Fever was induced by intraperitoneal injection of lipopolysaccharide at doses from 10 micrograms/kg to 2.5 mg/kg. Phenidone (20-30 mg/kg ip), a dual lipoxygenase and cyclooxygenase inhibitor, prevented fever in these mice, but esculetin (1-10 mg/kg ip), a selective inhibitor of lipoxygenases, did not affect fever. Intramuscular injection of nordihydroguaiaretic acid (10-20 mg/kg), a dual lipoxygenase and epoxygenase inhibitor, as well as SKF-525A (5 mg/kg ip) and clotrimazole (20 mg/kg im), inhibitors of the cytochrome P-450/epoxygenase pathway, augmented fever in mice. Indomethacin (5 mg/kg ip), an inhibitor of cyclooxygenase, suppressed the exacerbation of fever due to clotrimazole, suggesting that the epoxygenase inhibitor-induced potentiation of fever in mice is a prostaglandin-mediated effect. From this study, we hypothesize that the cytochrome P-450/epoxygenase branch of the arachidonate cascade is involved in antipyresis and in controlling the upper limit of fever.

Role of hypothalamic interleukin-1β in fever induced by cecal ligation and puncture in rats

Bacterial endotoxin induces fever by causing the release of interleukin (IL)-1β into the circulation or the brain. IL-1β is believed to mediate fever via triggering the production and/or release of IL-6 in the hypothalamus. The present study examined whether IL-1β and IL-6 in the hypothalamus of the rat are also involved in fever during bacterial sepsis caused by cecal ligation and puncture (CLP). CLP induces fever for 2 days. Polyclonal rabbit antibody against rat IL-1β (anti-IL-1β, 2 μg/μl) or control rabbit IgG (2 μg/μl) was unilaterally microinjected into the hypothalamus of rats immediately after or 24 h after CLP or sham-CLP surgery. Anti-IL-1β injected 24 h after CLP (when fever was already present) or sham-CLP surgery did not affect fever. Microinjection of anti-IL-1β into the hypothalamus immediately after surgery caused a significant decrease in body temperature during the night after CLP surgery and a 48% reduction of fever on the following day. Although blood plasma levels of IL-6 were significantly elevated 1.5, 6, 24, and 48 h after CLP surgery, there were no differences in IL-6 concentrations in the extracellular fluid of the anterior hypothalamus (collected by push-pull perfusion). These data suggest that fever due to bacterial sepsis is initiated by IL-1β within the hypothalamus, and this febrile response, unlike endotoxin-induced fever, is not accompanied by elevation in the hypothalamic concentration of IL-6.Bacterial endotoxin induces fever by causing the release of interleukin (IL)-1beta into the circulation or the brain. IL-1beta is believed to mediate fever via triggering the production and/or release of IL-6 in the hypothalamus. The present study examined whether IL-1beta and IL-6 in the hypothalamus of the rat are also involved in fever during bacterial sepsis caused by cecal ligation and puncture (CLP). CLP induces fever for 2 days. Polyclonal rabbit antibody against rat IL-1beta (anti-IL-1beta, 2 microg/microl) or control rabbit IgG (2 microg/microl) was unilaterally microinjected into the hypothalamus of rats immediately after or 24 h after CLP or sham-CLP surgery. Anti-IL-1beta injected 24 h after CLP (when fever was already present) or sham-CLP surgery did not affect fever. Microinjection of anti-IL-1beta into the hypothalamus immediately after surgery caused a significant decrease in body temperature during the night after CLP surgery and a 48% reduction of fever on the following day. Although blood plasma levels of IL-6 were significantly elevated 1.5, 6, 24, and 48 h after CLP surgery, there were no differences in IL-6 concentrations in the extracellular fluid of the anterior hypothalamus (collected by push-pull perfusion). These data suggest that fever due to bacterial sepsis is initiated by IL-1beta within the hypothalamus, and this febrile response, unlike endotoxin-induced fever, is not accompanied by elevation in the hypothalamic concentration of IL-6.

Role of Capsaicin-Sensitive Afferents in Fever and Cytokine Responses during Systemic and Local Inflammation in Rats

Objective: Peripheral afferents play an important role in fever. In the present study, we investigated the role of capsaicin-sensitive afferents in fever and cytokine responses during systemic (induced by intraperitoneal lipopolysaccharide, LPS) and local (induced by injection of Freund’s incomplete adjuvant, FIA, into the paw) inflammation. Methods: Fevers in rats (8–10 weeks of age) whose capsaicin-sensitive afferents were depleted by neonatal capsaicin (50 mg/kg) treatment were compared to those of rats treated as neonates with vehicle. To investigate a possible involvement of cytokines, plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF) were measured during LPS- and FIA-induced fever in rats after capsaicin-induced desensitization. Body temperature was measured by biotelemetry. IL-6 and TNF bioactivities in plasma were determined using bioassays. Results: The initial but not the late phase of LPS (50 µg/kg)-induced fever was markedly higher (∼1.0°C) in rats whose capsaicin-sensitive neurons were destroyed by neonatal capsaicin treatment. Capsaicin-induced desensitization also resulted in significantly higher plasma levels of IL-6 and TNF 1 but not 4 h after LPS challenge. In contrast, the day after injection with FIA (0.1 ml), rats treated with capsaicin had significantly lower body temperatures compared with vehicle-treated animals. No differences were found in plasma levels of IL-6 and TNF between capsaicin- and vehicle-treated animals in response to FIA. Conclusions: These data indicate that the role of capsaicin-sensitive afferents in fever depends on the type of inflammatory response. During systemic inflammation, capsaicin-sensitive afferents may be involved in modulating fever by regulating the levels of pyrogenic cytokines. During local inflammation, the late phase of fever is partially mediated via capsaicin-sensitive afferents.

Response of F344 rats to inhalation of subclinical levels of sarin: exploring potential causes of Gulf War illness

Subclinical, repeated exposures of F344 rats to sarin resulted in brain alterations in densities of chlonergic receptor subtypes that may be associated with memory loss and cognitive dysfunction. The exposures also depressed the immune system. The rat appears to be a good model for studying the effects of subclinical exposure to a nerve gas.

PULMONARY IMMUNITY TO RAGWEED IN A BEAGLE DOG MODEL OF ALLERGIC ASTHMA

To create an allergy model in the dog, allergic Beagles with high levels of serum immunoglobulin E(IgE) and eosinophilia were bred; resulting puppies were sensitized to ragweed by intraperitoneal (IP) injection within 24 hours of birth through 22 weeks of age. At least 50% of the puppies developed high levels of serum IgE and eosinophilia. As young adults, 6 of these dogs, and 6 control age-matched, nonallergic, nonimmunized dogs were exposed by inhalation to ragweed twice at 13-day intervals, and a third time 45 days later. Total and ragweed-specific serum IgE and ragweed-specific serum IgG were increased significantly in allergic dogs relative to baseline. Allergic dogs had significantly greater levels of antibody specific for ragweed, as well as higher eosinophil counts in the bronchoalveolar lavage fluid, compared to nonallergic dogs. Airway reactivity to histamine in allergic, but not nonallergic dogs, increased significantly after aerosol exposure to ragweed. After a third exposure to ragweed, airway responses to histamine were elevated in the allergic dogs and remained high for at least 5 months. These results demonstrate the potential of the allergic dog model for investigating the underlying pulmonary immune mechanisms and therapeutic treatment of allergic asthma.To create an allergy model in the dog, allergic Beagles with high levels of serum immunoglobulin E (IgE) and eosinophilia were bred; resulting puppies were sensitized to ragweed by intraperitoneal (IP) injection within 24 hours of birth through 22 weeks of age. At least 50% of the puppies developed high levels of serum IgE and eosinophilia. As young adults, 6 of these dogs, and 6 control age-matched, nonallergic, nonimmunized dogs were exposed by inhalation to ragweed twice at 13-day intervals, and a third time 45 days later. Total and ragweed-specific serum IgE and ragweed-specific serum IgG were increased significantly in allergic dogs relative to baseline. Allergic dogs had significantly greater levels of antibody specific for ragweed, as well as higher eosinophil counts in the bronchoalveolar lavage fluid, compared to nonallergic dogs. Airway reactivity to histamine in allergic, but not nonallergic dogs, increased significantly after aerosol exposure to ragweed. After a third exposure to ragweed, airway responses to histamine were elevated in the allergic dogs and remained high for at least 5 months. These results demonstrate the potential of the allergic dog model for investigating the underlying pulmonary immune mechanisms and therapeutic treatment of allergic asthma.

Parental allergic status influences the risk of developing allergic sensitization and an asthmatic‐like phenotype in canine offspring

Increasing evidence suggests that parental allergic status, especially that of the mother, may play a unique and important role in influencing the development of fetal infant immune responses to inhaled allergens, independently of genetic predisposition. We have developed an experimental model in dogs where the offspring from allergic parents, when exposed to inhaled allergen, develop allergic sensitization and an asthmatic phenotype, whereas the offspring from non‐allergic parents do not. Offspring from ragweed‐sensitized (two litters, n = 10) or non‐sensitized (two litters, n = 11) Beagle dogs were exposed repeatedly, by inhalation, to ragweed or filtered air (negative control) beginning within 1 week after birth. Serum levels of total immunoglobulin (Ig)E, and ragweed‐specific IgE and IgG, were measured at specific time‐points up to 40 weeks after birth. Cell differentials in the bronchoalveolar lavage were determined on days 1 and 4 following ragweed instillation into the offsprings lungs at 26 weeks of age. Changes in pulmonary resistance following challenge with histamine and ragweed (five breaths) were measured at 40 weeks after birth. Offspring from sensitized parents exposed to ragweed developed elevated serum total IgE and ragweed‐specific IgE and IgG, and showed an increased pulmonary resistance to histamine and ragweed, and increased numbers of eosinophils in bronchoalveolar lavage. In contrast, offspring from non‐sensitized parents did not exhibit this immune response. These results suggest that parental allergic sensitivity is important in the development of allergic sensitization and an asthmatic phenotype in the offspring.

Effect of Inhaled Ultrafine Carbon Particles on the Allergic Airway Response in Ragweed-Sensitized Dogs

Episodic increases in air pollution have been associated with the exacerbation of asthma symptoms. Ultrafine particles are a component of air pollution and may be involved in causing the adverse health effects associated with high air pollution. We evaluated the effects of ultrafine particle inhalation on immune and airway responses in a beagle dog model of allergic asthma. Six allergic (ragweed sensitive) and six nonallergic dogs were exposed to ultrafine carbon particles (232.3 ± 2.5 µg/m 3, 35.2 ± 0.3 nm) for 1 h, followed by a challenge with vehicle (water) as a negative control. Airway resistance was measured during particle exposure and after vehicle challenge. Immune responses 3 days before and after (1 h and 1, 4, 7, and 11 days) particle exposure were assessed by measuring total immunoglobulin E (IgE) and ragweed-specific IgE and IgG in serum and bronchoalveolar lavage fluid (BALF), and cell differentials in BALF. Each dog was exposed a second time to ultrafine carbon particles (251.4 ± 5.3 µg/m 3, 34.9 ± 0.5 nm) for 1 h followed by a challenge with ragweed and the same measurements. Airway resistance did not change during particle exposure in any of the dogs, and ragweed-induced airway reactivity was not altered by particle exposure. Total and ragweed-specific serum IgE and total IgE in BALF were higher in allergic dogs at all time points. Particle exposure did not affect antibody levels in serum or BALF in allergic dogs. Nonallergic dogs developed specific IgG in response to multiple inhalation exposures to ragweed, but this was not associated with particle exposure. Neutrophils were elevated in BALF for all groups 1 day after particle exposure. In conclusion, despite the induction of low level inflammation in the lungs of allergic and nonallergic dogs, exposure to ultrafine carbon particles did not alter airway reactivity or immune responses.

β-Adrenergic Receptor Subtype Effects on Stress Fever and Thermoregulation

Exposure to psychological stress increases body temperature (Tb). This stress fever may be immunologically beneficial in some patient populations but detrimental in others (e.g., HIV-infected individuals). For this reason, it is desirable to determine pharmacological methods of preventing stress fever. In rats, stress fever is modeled by exposure to a novel environment or ‘open field.’ The β-adrenergic antagonists, nadolol and propranolol, block this stress fever. Neither of these β-antagonists discriminates between subtypes of β-receptors. The purpose of this study was to determine the relative contribution of the different β-receptor types to stress fever using β1-, β2-, and β3-receptor subtype selective antagonists (atenolol [β1], ICI-118551 [β2], and SR 59230A [β3]) and agonists (dobutamine [β1], salbutamol [β2], and BRL 37344 [β3]) on the Tb of rats. Tb was measured with a biotelemetry system. Our data suggest that central nervous system β-receptor blockade with subtype-selective antagonists prevents the stress-induced rise in Tb; however, the β3-antagonist was effective only at doses that produced hypothermia in a non-stressed control group. The stress-induced fever was mimicked by central nervous system administration of the selective β2-agonist, salbutamol, and the β3-agonist, BRL 37344. We hypothesize that the blockade of stress-induced fever by β-blockers may be due to the sedative actions of these drugs.

Open Field-Induced Rise in Body Temperature and Plasma IL-6 Is Mediated by β-Adrenoceptors in the Braina

Exposure of rats to an open field, a mild psychological stressor, elevates body temperature and increases circulating interleukin-6 (IL-6). ‘3’ However, the pathway by which psychological stress triggers both responses is poorly recognized. Over the past few years, investigators increasingly have focused their attention on clarifying the possible involvement of the sympathetic nervous system in the psychological stress-induced rise in body temperature and plasma IL-6.3,4 Recently, we reported that pretreatment with L-propranolol, a nonselective /3-adrenoceptor antagonist, prevents the open field rise of body temperature and circulating 1L-6.5 The inhibitory effect of L-propranolol was observed after either peripheral (ip) or central (icv) injection of this blocking drug. Since L-propranolol can cross the blood-brain barrier by simple diffusion,6*’ we hypothesize that L-propranolol may prevent the effect of stress on body temperature and cytokine levels by competing for P-adrenoceptor sites inside the central nervous system. In addition, L-propranolol also has “local anesthetic” activity.8 This raises the possibility that its inhibitory effect may result not only from drug-receptor interactions but also from a tranquilizing effect due to the drug’s “local anesthetic” activity. The major hypothesis we have tested in this study is that P-adrenoceptors inside the blood-brain barrier are responsible for open field-induced elevation of body temperature and plasma IL-6 activity. To test our hypothesis, we used the unique properties of nadolol, a nonselective P-adrenoceptor antagonist. Nadolol has equivalent p-blocking properties to L-propranolol but is devoid of “local anesethetic” a ~ t i v i t y . ~ Moreover, because of its low lipophilicity, nadolol is unable to penetrate the blood-brain barrier.6