Misoprostol Inhibits Equine Neutrophil Adhesion, Migration, and Respiratory Burst in an In Vitro Model of Inflammation

Abstract

In many equine inflammatory disease states, neutrophil activities, such as adhesion, migration, and reactive oxygen species (ROS) production become dysregulated. Dysregulated neutrophil activation causes tissue damage in horses with asthma, colitis, laminitis, and gastric glandular disease. Non-steroidal anti-inflammatory drugs do not adequately inhibit neutrophil inflammatory functions and can lead to dangerous adverse effects. Therefore, novel therapies that target mechanisms of neutrophil-mediated tissue damage are needed. One potential neutrophil-targeting therapeutic is the PGE1 analog, misoprostol. Misoprostol is a gastroprotectant that induces intracellular formation of the secondary messenger molecule cyclic AMP (cAMP), which has been shown to have anti-inflammatory effects on neutrophils. Misoprostol is currently used in horses to treat NSAID-induced gastrointestinal injury; however, its effects on equine neutrophils have not been determined. We hypothesized that treatment of equine neutrophils with misoprostol would inhibit equine neutrophil adhesion, migration, and ROS production, in vitro. We tested this hypothesis using isolated equine peripheral blood neutrophils collected from 12 healthy adult teaching/research horses of mixed breed and gender. The effect of misoprostol treatment on adhesion, migration, and respiratory burst of equine neutrophils was evaluated via fluorescence-based adhesion and chemotaxis assays, and luminol-enhanced chemiluminescence, respectively. Neutrophils were pretreated with varying concentrations of misoprostol, vehicle, or appropriate functional inhibitory controls prior to stimulation with LTB4, CXCL8, PAF, lipopolysaccharide (LPS) or immune complex (IC). This study revealed that misoprostol pretreatment significantly inhibited LTB4-induced adhesion, LTB4-, CXCL8-, and PAF-induced chemotaxis, and LPS-, IC-, and PMA-induced ROS production in a concentration-dependent manner. This data indicate that misoprostol-targeting of E-prostanoid (EP) receptors potently inhibits equine neutrophil effector functions in vitro. Additional studies are indicated to further elucidate the role of EP receptors in regulating neutrophil function. Overall, our results suggest misoprostol may hold promise as a novel anti-inflammatory therapeutic in the horse.

Pharmacokinetics and ex vivo anti‐inflammatory effects of oral misoprostol in horses

“…Other anti-inflammatory effects of misoprostol occur at much lower concentrations than those associated with TNFa production. In vitro equine studies report that misoprostol concentrations as low as 0.001 umol/L (approximately 0.38 ng/mL) inhibit LPS-induced equine neutrophil respiratory burst [36], which is much more similar to the concentrations obtained in this study. Therefore, it is possible that misoprostol will affect leucocyte function directly and indirectly through its actions on other cell types in vivo.…”

Misoprostol is superior to combined omeprazole‐sucralfate for the treatment of equine gastric glandular disease

“…Misoprostol is a prostaglandin E 1 analogue that is licensed for the treatment of refractory glandular disease in human patients. It has a number of effects on the stomach in other species which include doserelated inhibition of gastric acid and pepsin production and secretion, enhancement of mucosal resistance to injury, promotion of gastric mucosal proliferation in humans and dogs [31], increases gastric mucosal blood flow and has anti-inflammatory properties [32,33]. One experimental study in horses demonstrated that misoprostol effectively suppresses acid production and secretion in the horse and, when compared with oral omeprazole, this effect was shown to be longer in duration [34].…”

Recommendations for the management of equine glandular gastric disease

“…Misoprostol is a prostaglandin analogue and an increasingly popular treatment for EGGD that has multiple mechanisms of action that may be of benefit. Misoprostol suppresses acid production (Sangiah et al, 1989) and inhibits neutrophilic inflammation (Martin et al, 2017) and is therefore a logical treatment for EGGD. However, there is limited evidence of its efficacy.…”