Identification and Quantification of Transient Receptor Potential Vanilloid 1 (TRPV1) in Equine Articular Tissue

Abstract

Joint pain and osteoarthritis (OA) are some of the most common causes of lameness in horses, and most of the available treatments focus on symptomatic relief without a disease-modifying effect. TRPV1 is a potential target for treating joint diseases, including OA, and the present study aims to investigate if the TRPV1 receptor is present in equine articular tissue and determine whether the number of receptors is upregulated in joint inflammation. Metacarpo/metatarsophalangeal (MCP/MTP) joints from 15 horses euthanised for reasons unrelated to this study were included. Based on synovial fluid analysis, macroscopic evaluation, and magnetic resonance imaging (MRI), joints were divided into two groups: healthy joints and joints with pathology. ELISA analysis was performed on synovial tissue harvested from all joints. TPRV1 was found in all joints. The mean concentration of TRPV1 compared to total protein in healthy joints (8.4 × 10 −7 ng/mL) and joints with pathology (12.9 × 10 −7 ng/mL) differed significantly (p = 0.01, t-test with Welch correction). Quantitative real-time reverse transcriptase PCR analysis was performed on RNA isolates from synovial tissue from all joints. TRPV1 mRNA expression ratio normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in healthy joints (0.16 (SD: 0.19)) and joints with pathology (0.24 (SD: 0.14)) did not differ significantly (p = 0.43, t-test with Welch correction). mRNA expression of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) was very low for both groups. In conclusion, TRPV1 was detected both on mRNA and the protein level, with a higher expression of TRPV1 in samples from joints with pathology. Future studies will determine the clinical potential of equine TRPV1 as a target in the management of joint pain and inflammation.Animals 2020, 10, 506 2 of 15 described aetiology is trauma-either as a single event or as a series of microtrauma. This will induce an inflammatory response, which, in turn, will drive the process of articular cartilage breakdown and remodelling of the surrounding bone [4]. Consequently, horses diagnosed with OA are often retired or euthanised.There is a broad spectrum of treatments for equine OA. Most of them are anti-inflammatory and pain-relieving without a true disease-modifying effect, although regenerative medicine in regard to equine OA is a rapidly evolving area [5][6][7][8]. Two of the drug groups most commonly used for treating the symptoms related to equine OA are nonsteroidal anti-inflammatory drugs (NSAIDs) and intra-articular corticosteroids, often in combination. NSAIDs are predisposing for gastrointestinal ulceration and are potentially nephrotoxic, and corticosteroids are potentially chondrotoxic [9][10][11][12]. In human medicine, so-called disease-modifying osteoarthritis drugs (DMOADs) are being investigated in an attempt to stop the disease progression, as well as being pain-relieving and anti-inflammatory. However, an effective disease-modifying drug has not yet been developed [13].Several authors point to the ...

Expression of cannabinoid (CB1 and CB2) and cannabinoid-related receptors (TRPV1, GPR55, and PPARα) in the synovial membrane of the horse metacarpophalangeal joint

“…To date, the gene expression has been reported in the equine synovial membrane only for TRPV1 (4). The present study confirmed the expression of TRPV1 and also demonstrated the expression of Cnr1, Cnr2, GPR55, and PPARA, according to the Authors' protein data.…”

“…The metacarpophalangeal joint is a high mobility structure which undergoes enormous loading during locomotion and jumping in the horse (1), so much so that it is the most commonly reported joint affected by traumatic and degenerative lesions in equine athletes (2) and results in lameness in thoroughbred racehorses (3,4). Currently, there is no specific cure for joint disease, and the multimodal pharmacological treatment does not act on the cause of joint inflammation but is aimed at slowing its progression, minimizing/reducing pain, and increasing function and performance (5).…”

“…Given the aforementioned data obtained in other species, it is conceivable that the receptors of the endocannabinoid system could be expressed in the horse synovial membrane and represent a pharmacological target for the treatment of joint diseases. Currently, only a few reports have been published regarding the cannabinoid and cannabinoid-related receptors of the horse joint synovium (4,44).…”

A standardized extract of Centella asiatica (ECa 233) prevents temporomandibular joint osteoarthritis by modulating the expression of local inflammatory mediators in mice

“…5 A previous study reported that the total protein levels of TRPV1 in osteoarthritis (OA) were higher than those found in healthy joints. 6 ASIC3 is a sodium-selective ion channel activated by low extracellular pH and a member of the degenerin sodium channel superfamily. It is a pain modulator expressed in the knee joint, strongly correlated with weight-bearing pain and secondary hyperalgesia.…”

Alterations in Anandamide Synthesis and Degradation during Osteoarthritis Progression in an Animal Model

“…However, AEA may interact and activate other targets, such as the transient receptor potential vanilloid type 1 (TRPV1) [ 15 ]. TRPV1 was originally reported to be expressed on the peripheral nociceptive afferents and is present in the spinal and supraspinal structures [ 16 ]; TRPV1 is also expressed in multiple cell types of the joint [ 17 , 18 , 19 ]. Interestingly, a variant of the TRPV1 gene is associated with the risk of the development of symptomatic OA [ 20 ].…”