USDA-ARS Forage-Animal Production Research Unit, University of Kentucky Campus, 1100 S. Limestone Rd. N220 Ag. Science North, Lexington, KY, 40546, USA.
BMC Vet Res. 2024 Oct 22;20(1):481. doi: 10.1186/s12917-024-04319-x.
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.
内源性大麻素系统（ECS）与身体的几乎所有生理和病理生理过程高度整合。人们越来越感兴趣的是利用生物活性植物化合物来促进健康和提高牲畜的生产力。鉴于植物化学物质与 ECS 之间已确立的相互作用，有许多机会可以识别和开发治疗方法来解决一系列疾病和障碍。然而，ECS 在牛中，特别是在胃肠道中，尚未得到充分描述。本研究的目的是描述与牛组织中的内源性大麻素系统相关的基因的分布和转录丰度。
从 10 月龄荷斯坦公牛（n = 6）中采集脑、脾、甲状腺、肺、肝、肾、肠系膜静脉、舌、舌下黏膜、瘤胃、网胃、十二指肠、空肠、回肠和结肠等组织。提取总 RNA，并使用绝对定量实时 qPCR 测量基因表达。测量内源性大麻素受体 CNR1 和 CNR2、合成酶 DAGLA、DAGLB 和 NAPEPLD、降解酶 MGLL 和 FAAH 以及瞬时受体电位香草素 TRPV3 和 TRPV6 的基因表达。在 R 中使用 Kruskal-Wallis followed by a Wilcoxon rank-sum test 进行数据分析。结果以 20ng 等效 cDNA（CN）的中位数拷贝数/20ng （CN）表示，四分位距（IQR）。
CNR1 和 CNR2 的最大表达分别在大脑和脾脏中。任何胃肠道组织中均未检测到任何一种受体的表达，但在瘤胃中，CNR2 的表达有高于背景的趋势（P = 0.095）。内源性大麻素合成和降解酶的表达在组织间差异很大。脑组织中 DAGLA 的表达最高，为 641 CN（IQR 52；P≤0.05）。DAGLB 在所有组织中均有检测到，大脑和脾脏的表达最高（P≤0.05）。在舌和舌下黏膜中，胃肠道组织中 NAPEPLD 的表达最低。后肠组织之间的 NAPEPLD 表达没有差异，但这些组织的表达比瘤胃和网胃高 592%（P≤0.05）。虽然 MGLL 被发现存在于所有组织中，但 FAAH 的表达仅在大脑、肝、肾、空肠和回肠中高于检测限。TRPV3 在舌、瘤胃、网胃和结肠中的表达高于背景。尽管彼此之间没有差异，但甲状腺和十二指肠中 TRPV6 的表达最大，分别为 285（IQR 164）和 563（IQR 467）CN，与所有其他组织相比（P<0.05）。
这些数据表明 ECS 在牛组织中的分布和变化复杂。表达模式表明该系统的调节功能具有组织依赖性，为研究 ECS 的潜在靶组织提供了初步见解。
