Mitogen-activated kinase pathway activation in epidermal lamellae in the acute stages of carbohydrate overload laminitis models and the effect of regional deep hypothermia on signalling pathways

• Published in: Equine veterinary journal 2016-09, Vol.48 (5), p.633-640
• Main Authors: Gardner, A. K., Kelly, C. S., van Eps, A. W., Burns, T. A., Watts, M. R., Belknap, J. K.
• Format: Article
• Language: English
• Subjects: Animals; c-Jun protein; Carbohydrates; Cold Temperature; Dietary Carbohydrates - adverse effects; digital lamellae; Epidermis; Extracellular signal-regulated kinase; Fever; Foot Diseases - chemically induced; Foot Diseases - metabolism; Foot Diseases - veterinary; Fructooligosaccharides; Hoof and Claw - metabolism; Hoof and Claw - pathology; horse; Horse Diseases - chemically induced; Horse Diseases - metabolism; Horses; Hypothermia; Ice; Immunoblotting; Inflammation; Inflammation - chemically induced; Inflammation - metabolism; Inflammation - veterinary; Kinases; Lamellae; laminitis; Limbs; MAP kinase; MAP Kinase Signaling System - physiology; mitogen-activated protein kinase; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Proteins; Samples; Sepsis; Signal transduction; Starch; Statistical analysis; Tissues; Transcription factors
• ISSN: 0425-1644; 2042-3306
• DOI: 10.1111/evj.12488

Summary Reasons for performing study In sepsis models, mitogen‐activated protein kinases (MAPKs) are reported to incite inflammatory injury to tissues and are purported to be a therapeutic target. Objectives To assess MAPK signalling in lamellae in sepsis‐related laminitis (SRL) at different time points after induction of laminitis via carbohydrate overload, and to determine the effect of regional deep hypothermia (RDH) on MAPK signalling. Study design In vitro study using archived tissue samples. Methods Lamellar concentrations of MAPKs were assessed in archived lamellar samples from 2 studies: 1) the starch gruel model of SRL with 3 groups (n = 6/group) of horses (control, onset of fever [DEV] Obel Grade 1 lameness [OG1]); and 2) from limbs maintained at ambient (AMB) and hypothermic (ICE) temperatures (n = 6/group) in animals given a bolus of oligofructose. Immunoblotting and immunolocalisation were used to assess lamellar concentrations and cellular localisation of total and activated (phosphorylated) forms of p38 MAPK, extracellular‐regulated kinase (ERK) 1/2, and stress‐activated protein kinase/c‐jun N terminal kinase (SAPK/JNK) 1/2. Results Lamellar samples had statistically significant increased concentrations of activated ERK 1/2 at the onset of OG1 laminitis (vs. control) in the starch gruel model, but showed no significant change between ICE and AMB limbs in the RDH model. Phospho‐SAPK/JNK 1/2 exhibited a similar significant increase in the OG1 samples, but was also increased in ICE (vs. AMB) limbs. No statistically significant changes in lamellar p38 MAPK concentrations were noted. Conclusions Increased concentrations of activated ERK 1/2 and SAPK/JNK in the acute stages of SRL indicate a possible role of these signalling proteins in lamellar injury. Signalling related to ERK 1/2 and SAPK/JNK 1/2 pathways should be further investigated to determine if these play a detrimental role in laminitis and may be therapeutic targets to be manipulated independently of RDH.