The endocannabinoid system in bovine tissues: characterization of transcript abundance in the growing Holstein steer

Authors: KENT-DENNIS, CORAL - Oak Ridge Institute For Science And Education (ORISE); Klotz, James

Submitted to: BMC Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2024
Publication Date: 10/22/2024
Citation: Kent-Dennis, C., Klotz, J.L. 2024. The endocannabinoid system in bovine tissues: characterization of transcript abundance in the growing Holstein steer. BMC Veterinary Research. 20. Article 481. https://doi.org/10.1186/s12917-024-04319-x.
DOI: https://doi.org/10.1186/s12917-024-04319-x

Interpretive Summary: The endocannabinoid system is integrated throughout the body and involved in numerous processes in humans and rodents. Many plant-derived compounds can interact with the endocannabinoid system and cause beneficial effects. Research in this area has the potential for development of therapies that can aid with the treatment of various diseases and disorders. Information is lacking, however, on the endocannabinoid system in ruminants. Thus, the goal of this project was to characterize the expression of genes associated with the endocannabinoid system in cattle. A range of tissue samples were collected after slaughter from cattle brain, tongue, sublingual mucosa, rumen, omasum, duodenum, jejunum, ileum, colon, thyroid, lung, liver, kidney, spleen, and mesenteric vein. The results demonstrated a varied distribution of genes associated with synthesis, metabolism, and receptors. This study provides insight into potential targets for manipulation of the endocannabinoid system in cattle production systems. This work will primarily benefit other researchers looking for opportunities to manipulate the endocannbinoid system to improve cattle health and productivity.

Technical Abstract: The endocannabinoid system (ECS) is highly integrated with seemingly all physiological and pathophysiological processes in the body. There is increasing interest in utilizing bioactive plant compounds, for promoting health and improving production in livestock. Given the established interaction between phytochemicals and the ECS, there are many opportunities for identification and development of therapies to address a range of diseases and disorders. However, the ECS has not been thoroughly characterized in cattle, especially in the gastrointestinal tract. The objective of this study was to characterize the distribution and transcriptional abundance of genes associated with the endocannabinoid system in bovine tissues. Tissues including brain, spleen, thyroid, lung, liver, kidney, mesenteric vein, tongue, sublingual mucosa, rumen, omasum, duodenum, jejunum, ileum and colon were collected from 10-mo old Holstein steers (n = 6). Total RNA was extracted and gene expression was measured using absolute quantification real time qPCR. Gene expression of endocannabinoid receptors CNR1 and CNR2, synthesis enzymes DAGLA, DAGLB and NAPEPLD, degradation enzymes MGLL and FAAH, and transient receptor potential vanilloids TRPV3 and TRPV6 was measured. Data were analyzed in R using a Kruskal-Wallis followed by a Wilcoxon rank-sum test. Results are reported as the median copy number/20 ng of equivalent cDNA (CN) with interquartile range (IQR). The greatest expression of CNR1 and CNR2 was in the brain and spleen, respectively. Expression of either receptor was not detected in any gastrointestinal tissues, however there was a tendency (P = 0.095) for CNR2 to be expressed above background in rumen. Expression of endocannabinoid synthesis and degradation enzymes varied greatly across tissues. Brain tissue had the greatest DAGLA expression at 641 CN (IQR 52; P = 0.05). DAGLB was detected in all tissues, with brain and spleen having the greatest expression (P = 0.05). Expression of NAPEPLD in the gastrointestinal tract was lowest in tongue and sublingual mucosal. There was no difference in expression of NAPEPLD between hindgut tissues, however these tissues collectively had 592% greater expression than rumen and omasum (P = 0.05). While MGLL was found to be expressed in all tissues, expression of FAAH was only above the limit of detection in brain, liver, kidney, jejunum and ileum. TRPV3 was expressed above background in tongue, rumen, omasum and colon. Although not different from each other, thyroid and duodenum had the greatest expression of TRPV6, with 285 (IQR 164) and 563 (IQR 467) CN compared to all other tissues (P < 0.05). These data demonstrate the complex distribution and variation of the ECS in bovine tissues. Expression patterns suggest that regulatory functions of this system are tissue dependent, providing initial insight into potential target tissues for manipulation of the ECS.