Endotoxin fever in granulocytopenic rats: evidence that brain cyclooxygenase-2 is more important than circulating prostaglandin E2

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.

Anti-inflammatory activity of 2-((3-(chloromethyl)benzoyl)oxy)benzoic acid in LPS-induced rat model

INTRODUCTION

Salicylic acid derivate is very popular for its activity to suppress pain, fever, and inflammation. One of its derivatives is acetylsalicylic acid (ASA) which has been reported repeatedly that, as a non-steroidal anti-inflammatory drug (NSAID), it has a cardioprotective effect. Although ASA has various advantages, several studies have reported that it may induce severe peptic ulcer disease. We recently synthesized a new compound derived from salicylic acid, namely 2-((3-(chloromethyl)benzoyl)oxy)benzoic acid (3-CH₂Cl) which still has the benefit of acetylsalicylic acid as an analgesic and antiplatelet, but lacks its harmful side effects (Caroline et al., 2019). In addition, in silico studies of 3-CH₂Cl showed a higher affinity towards protein receptor cyclooxygenase-2 (COX-2; PDB: 5F1A) than ASA. We hypothesized that 3-CH₂Cl inhibits the COX-2 activity which could presumably decrease the inflammatory responses. However, no knowledge is available on the anti-inflammatory response and molecular signaling of this new compound. Hence, in this study, we investigated the potential functional relevance of 3-CH₂Cl in regulating the inflammatory response in lipopolysaccharide (LPS)-induced rats. The results of this study show that this compound could significantly reduce the inflammatory parameter in LPS-induced rats.

MATERIAL AND METHODS

Rats were induced with LPS of 0.5 mg/kg bw intravenously, prior oral administration with vehicle (3% Pulvis Gummi Arabicum / PGA), 500 mg/60 kg body weight (bw; rat dosage converted to human) of 3-CH₂Cl and ASA. The inflammatory parameters such as changes in the temperature of septic shock, cardiac blood plasma concentrations of IL-1β and TNF-α (ELISA), blood inflammation parameters, white blood cell concentrations, and lung histopathology were observed. Meanwhile, the stability of 3-CH₂Cl powder was evaluated.

RESULT

After the administration of 500 mg/60 kg bw of 3-CH₂Cl (rat dosage converted to human) to LPS-induced rats, we observed a significant reduction of both TNF-α (5.70+/-1.04 × 10³ pg/mL, p=<0.001) and IL-1β (2.32+/-0.28 × 10³ pg/mL, p=<0.001) cardiac blood plasma concentrations. Besides, we found a reduction of white blood cell concentration and the severity of lung injury in the 3-CH₂Cl group compared to the LPS-induced rat group. Additionally, this compound maintained the rat body temperature within normal limits during inflammation, preventing the rats to undergo septic shock, characterized by hypothermic (t = 120 min.) or hyperthermic (t = 360 min) conditions. Furthermore, 3-CH₂Cl was found to be stable until 3 years at 25°C with a relative humidity of 75 ± 5%.

CONCLUSION

3-CH₂Cl compound inhibited inflammation in the LPS-induced inflammation response model in rats, hypothetically through binding to COX-2, and presumably inhibited LPS-induced NF-κβ signaling pathways. This study could be used as a preliminary hint to investigate the target molecular pathways of 3-CH₂Cl as a novel and less toxic therapeutical agent in alleviating the COX-related inflammatory diseases, and most importantly to support the planning and development of clinical trial.

An inflammatory vascular endothelium-mimicking microfluidic device to enable leukocyte rolling and adhesion for rapid infection diagnosis

Recruitment of circulating leukocytes to sites of infection is of utmost importance in the development, propagation, and outcome of sepsis. These multi-step processes are mediated by interactions between adhesion receptors of leukocytes and cell adhesion molecules (CAMs) of endothelial cells, such as P-selectin, E-selectin and ICAM-1. However, the potential utility of the CAMs-facilitated leukocyte capture has not been thoroughly investigated as an index of the host response to infection for diagnostic purposes. Here, we report that the systemic infection affects the expression of CAMs ligands on leukocytes, upregulating the expression of P-selectin ligand-1 (PSGL-1) and increasing the number of PSGL-1- and E-selectin ligand-1 (ESL-1)-expressing leukocyte levels in septic blood. We leveraged this finding to determine infection by measuring the increased adhesion of leukocytes to an inflammatory vascular endothelium-mimicking microchannel coated with CAMs. We successfully validated that the proposed method can significantly differentiate infection in bacteremia and endotoxemia models in rats as early as an hour post-infection using a finger-prick volume of blood (50 μL), which were unachievable with the conventional diagnostic methods.

Fever and hypothermia in systemic inflammation

Systemic inflammation-associated syndromes (e.g., sepsis and septic shock) often have high mortality and remain a challenge in emergency medicine. Systemic inflammation is usually accompanied by changes in body temperature: fever or hypothermia. In animal studies, systemic inflammation is often modeled by administering bacterial lipopolysaccharide, which triggers autonomic and behavioral thermoeffector responses and causes either fever or hypothermia, depending on the dose and ambient temperature. Fever and hypothermia are regulated changes of body temperature, which correspond to mild and severe forms of systemic inflammation, respectively. Mediators of fever and hypothermia are called endogenous pyrogens and cryogens; they are produced when the innate immune system recognizes an infectious pathogen. Upon an inflammatory challenge, hepatic and pulmonary macrophages (and later brain endothelial cells) start to release lipid mediators, of which prostaglandin (PG) E₂ plays the key role, and cytokines. Blood PGE₂ enters the brain and triggers fever. At later stages of fever, PGE₂ synthesized within the blood-brain barrier maintains fever. In both cases, PGE₂ is synthesized by cyclooxygenase-2 and microsomal PGE₂synthase-1. Mediators of hypothermia are not well established. Both fever and hypothermia are beneficial host defense responses. Based on evidence from studies in laboratory animals and clinical trials in humans, fever is beneficial for fighting mild infection. Based mainly on animal studies, hypothermia is beneficial in severe systemic inflammation and infection.

Antipyretic therapy: clinical pharmacology

Fever depends on a complex physiologic response to infectious agents and other conditions. To alleviate fever, many medicinal agents have been developed over a century of trying to improve upon aspirin, which was determined to work by inhibiting prostaglandin synthesis. We present the process of fever induction through prostaglandin synthesis and discuss the development of pharmaceuticals that target enzymes and receptors involved in prostaglandin-mediated signal transduction, including prostaglandin H₂ synthase (also known as cyclooxygenase), phospholipase A₂, microsomal prostaglandin E₂ synthase-1, EP receptors, and transient potential cation channel subfamily V member 1. Clinical use of established antipyretics will be discussed as well as medicinal agents under clinical trials and future research.

Behavioral fever in ectothermic vertebrates

Fever is an evolutionary conserved defense mechanism which is present in both endothermic and ectothermic vertebrates. Ectotherms in response to infection can increase their body temperature by moving to warmer places. This process is known as behavioral fever. In this review, we summarize the current knowledge on the mechanisms of induction of fever in mammals. We further discuss the evolutionary conserved mechanisms existing between fever of mammals and behavioral fever of ectothermic vertebrates. Finally, the experimental evidences supporting an adaptive value of behavioral fever expressed by ectothermic vertebrates are summarized.

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

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

Pharmacological characterization of a selective COX-2 inhibitor MF-tricyclic, [3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone], in multiple preclinical species

Selective type 2 cyclooxygenase (COX-2) inhibitors are often used in preclinical studies without potency and selectivity data in the experimental species. To address this issue, we assessed a selective COX-2 inhibitor MF-tricyclic in four commonly used species, namely mice, rats, guinea pigs and rabbits, in the present study. In both the guinea pig and rabbit whole blood assay, the compound inhibited lipopolysaccharide (LPS)-induced PGE(2) production with an IC(50) (COX-2) of 0.6 and 2.8 microM, respectively. By comparison, the compound displayed a much weaker activity on clot-induced formation of thromboxane with an IC(50) (COX-1) of >10 microM (guinea pigs) and 23 microM (rabbits). In keeping with the in vitro potency data, the compound significantly inhibited interleukin-1 beta (IL-1beta) -induced PGE(2) formation in the rabbit synovium at plasma concentrations near the whole blood assay IC(50) for COX-2 but much lower than that for COX-1. MF-tricyclic was also potent and selective toward COX-2 in mice, inhibiting carrageenan-induced PGE(2) accumulation in the air pouch dose-dependently (ED(50)=0.5 mg/kg) without affecting stomach PGE(2) levels. In rats, MF-tricyclic was found to be effective in three standard in vivo assays utilized for assessing COX-2 inhibitors, namely, LPS-induced pyresis, carrageenan-induced paw edema and adjuvant-induced arthritis at the doses that did not inhibit stomach PGE(2) levels. Similar to that in rats, the compound displayed pharmacological efficacy in mice, guinea pigs and rabbits when tested in the LPS pyresis model. Our data reveal that MF-tricyclic has the desired biochemical and pharmacological properties for selective COX-2 inhibition in all four test species.