Determination of milk concentrations and pharmacokinetics of salicylic acid following acetylsalicylic acid (aspirin) administration in postpartum dairy cows.

The objectives of this descriptive study were to (1) describe the pharmacokinetics of salicylic acid (SA) in the milk and plasma of postpartum dairy cattle following oral administration of acetylsalicylic acid (ASA; aspirin), (2) to estimate a recommended milk withdrawal period for dairy cattle treated with ASA, and (3) to determine the effect of ASA administration on plasma prostaglandin E2 metabolite (PGEM) concentrations. Primiparous (n = 3) and multiparous (n = 7) postpartum Holstein dairy cows received 2 oral treatments with ASA at 200 mg/kg of body weight, 24 h apart. Concentrations of SA in plasma and milk from 0 h through 120 h after ASA administration were analyzed using ultra performance liquid chromatography triple quadrupole mass spectrometry and a milk withdrawal period was estimated using the United States Food and Drug Administration Milk Discard App in R. Two withdrawal periods were estimated: (1) a whole-herd treatment scenario with no dilution factor and (2) an individual animal treatment scenario with a bulk tank factor included in analysis. Plasma PGEM concentrations in samples from 0 h to 24 h after ASA administration were determined using a commercially available competitive ELISA. Milk SA concentrations were undetected in all cows by 48 h after the last ASA treatment. Secondary peaks were observed in plasma at 58 and 82 h after the last treatment and in milk at 87 h after the last treatment. In the absence of a tolerance for SA in milk, the estimated milk withdrawal periods were (1) 156 h for the whole-herd treatment scenario and (2) 120 h for the individual animal treatment scenario. Plasma PGEM concentrations were reduced compared with baseline for up to 12 h after ASA administration, with the greatest reduction observed at 2 h. Results from this study suggest that the current milk withhold recommendation for dairy cattle administered ASA may need revision to 120 h (5 d) and that ASA administration may mitigate postpartum inflammation through reduction in prostaglandin production for up to 12 h after treatment. Pharmacokinetic and milk withdrawal data from this study will inform future recommendations for extra-label use of aspirin in postpartum dairy cows. Further research is required to determine the basis for the secondary SA peaks and to elucidate the long-term effects of ASA administration on dairy cow health.

Epigenetic silencing of the intronic microRNA hsa-miR-342 and its host gene EVL in colorectal cancer.

MicroRNAs are small, non-coding RNAs that influence gene regulatory networks by post-transcriptional regulation of specific messenger RNA targets. MicroRNA expression is dysregulated in human malignancies, frequently leading to loss of expression of certain microRNAs. We report that expression of hsa-miR-342, a microRNA encoded in an intron of the gene EVL, is commonly suppressed in human colorectal cancer. The expression of hsa-miR-342 is coordinated with that of EVL and our results indicate that the mechanism of silencing is CpG island methylation upstream of EVL. We found methylation at the EVL/hsa-miR-342 locus in 86% of colorectal adenocarcinomas and in 67% of adenomas, indicating that it is an early event in colorectal carcinogenesis. In addition, we observed a higher frequency of methylation (56%) in histologically normal colorectal mucosa from individuals with concurrent cancer compared to mucosa from individuals without colorectal cancer (12%), suggesting the existence of a 'field defect' involving methylated EVL/hsa-miR-342. Furthermore, reconstitution of hsa-miR-342 in the colorectal cancer cell line HT-29 induced apoptosis, suggesting that this microRNA could function as a proapoptotic tumor suppressor. In aggregate, these results support a novel mechanism for silencing intronic microRNAs in cancer by epigenetic alterations of cognate host genes.

Regulation of the mRNAs encoding proteins of the BMP signaling pathway during the maternal stages of Xenopus development.

Activation of the Xenopus bone morphogenetic protein (BMP) pathway is coincident with the onset of zygotic transcription but requires maternal signaling proteins. The mechanisms controlling the translation of mRNAs that encode proteins of the BMP pathway were investigated by using polysome association as an assay for translational activity. Our results indicate that five different mRNAs encoding proteins of the BMP pathway were translationally regulated during Xenopus development. These mRNAs were either not associated or inefficiently associated with polysomes in oocytes, and each was recruited to polysomes at a different developmental stage. The Smad1 and ALK-2 mRNAs were recruited to polysomes during oocyte maturation, whereas the BMP-7 and XSTK9 mRNAs were recruited during the early stages of embryogenesis. The ALK-3 mRNA was not efficiently associated with polysomes during any maternal stage of development and was efficiently recruited to polysomes only after the onset of zygotic transcription. In general, for all stages except oocytes, polysome recruitment was associated with the presence of a 3' poly(A) tail. However, there was not an obvious correlation between the absolute length of poly(A) and the efficiency of polysome recruitment, indicating that the relationship between poly(A) tail length and translation during early frog embryogenesis is complex. We further focused on the BMP-7 mRNA and demonstrated that sequence elements within the 3'UTR were necessary for recruitment of the BMP-7 mRNA to polysomes and sufficient to direct the addition of poly(A) and activate translation of a reporter during embryogenesis. Interestingly, the BMP-7 mRNA lacks the previously defined eCPE sequences proposed to direct poly(A) addition and translational activation during embryogenesis. The implications of our findings for translational regulation of maternal mRNAs during embryogenesis and for the activation of the BMP pathway are discussed.