Effects of niacin and betaine on bovine mammary and uterine cells exposed to thermal shock in vitro

The objective of this study was to investigate the direct effects of feed supplements niacin and betaine on the heat shock responses of in vitro cultured cells derived from bovine mammary and uterine tissues. First, we determined the mRNA expression profiles of the niacin receptor (GPR109A) in bovine tissues (liver, skin, uterus, udder, and ovary) and in cells derived from bovine mammary epithelium (mammary alveolar cells, MAC-T; bovine mammary epithelial cells, BMEC) and endometrium (bovine endometrial cells, BEND). We found that GPR109A was distributed in all examined tissues and cells, and the highest expression was in cells from skin and udder. Second, we evaluated the effects of niacin treatment on the mRNA abundance of heat shock proteins 70 and 27 (HSP70 and HSP27) in MAC-T, BMEC, and BEND under thermoneutral conditions and heat stress, and whether these effects were associated with alterations in the mRNA expression of prostaglandin E2 synthesis–related genes, including cyclooxygenase 1 and 2 (COX-1 and COX-2) and microsomal prostaglandin E synthase 1 and 2 (mPGES-1 and mPGES-2). Quantitative PCR data indicated that niacin suppressed HSP70 mRNA expression in BMEC and both HSP70 and HSP27 in BEND under thermoneutral conditions. Only COX-2 expression was downregulated by niacin in BMEC; other prostaglandin E2 synthesis–related genes stayed unaltered in BMEC and BEND. The mRNA abundance of HSP70, COX-1, COX-2, and mPGES-1 were elevated in niacin-treated MAC-T. During heat stress, niacin increased mRNA levels of HSP70 and HSP27 in MAC-T and HSP27 in BEND, but decreased HSP70 in BMEC. Although mPGES-2 was stimulated by niacin in BEND, the mRNA expression of prostaglandin E2 synthesis–related genes were consistent with neither HSP70 nor HSP27 expression patterns in niacin-treated BMEC and MAC-T. These data suggest that the effects of niacin on heat shock protein expression and prostaglandin E2 synthesis were not well coupled in these cells. Finally, we tested the effects of betaine treatment on viability and apoptosis in BMEC. Compared with control cultures, viability was higher in betaine-treated cells at 8 h under thermoneutral conditions and at 16 h in heat stress, and apoptotic rates were lower at 8 h. Our data support a dual role for niacin in regulating heat shock protein expression in normal and heat-shocked cells derived from mammary and uterine tissues, and positive effects of betaine in regulating mammary cell viability during heat stress.