title: Short communication: Effect of heat stress on markers of autophagy in the mammary gland during the dry period.
abstract: Heat stress (HT) during the dry period compromises mammary gland (MG) growth, thus negatively affecting subsequent milk yield. Cooling during the late dry period, when mammary tissue proliferates, is a common management practice. However, it neglects MG involution during the early dry period, a process that is accomplished by both apoptosis and autophagy. Our objective was to evaluate the effect of HT on MG autophagy during the early dry period. Holstein cows were dried off ~45d before expected calving and randomly assigned to 1 of 2 treatments: HT or cooling (CL). All cows were housed in the same free stall barn during the dry period, but only the stall area for CL cows was equipped with soakers and fans. Rectal temperature and respiration rate were measured daily during the dry period. Mammary gland biopsies were collected from each cow 3d before dry-off and on d 3, 7, 14, and 22±2 after dry-off. Autophagy in the MG was determined by measuring protein expression of 2 autophagic markers, autophagy-related protein 7 and microtubule-associated protein light chain 3 (LC3). The average temperature-humidity index during the dry period was 77.7, which indicated that HT and CL cows were exposed to significant heat stress. However, the cooling system effectively alleviated heat strain in CL cows by decreasing the rectal temperature (39.0 vs. 39.4°C) and respiration rate (47.3 vs. 71.2 breaths per minute) relative to HT cows. Protein expression of autophagy-related protein 7, a marker for early autophagosome formation, did not change within or between groups. In contrast, protein expression of LC3-II, a marker of autophagosomes, and its precursor LC3-I showed a dynamic expression pattern in MG from CL cows during the early dry period. Relative to HT cows, MG from CL cows displayed higher expression of LC3-I and LC3-II on d 7 and lower expression of LC3-II on d 14 and 22 after dry-off. Collectively, our data provide a possible mechanistic explanation for the impairment of MG capacity in HT dairy cows. Heat stress-related perturbations of autophagic activity may compromise the regenerative MG involution that is necessary for optimal cell proliferation.
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611. Electronic address: steffiw@ufl.edu.
authors.forename: S E
authors.initials: SE
authors.lastname: Wohlgemuth
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611.
authors.forename: Y
authors.initials: Y
authors.lastname: Ramirez-Lee
authors.affiliation: Department of Animal and Dairy Science, University of Georgia, 2360 Rainwater Road, Tifton 31793-5766.
authors.forename: S
authors.initials: S
authors.lastname: Tao
authors.affiliation: Department of Animal and Dairy Science, University of Georgia, 2360 Rainwater Road, Tifton 31793-5766.
authors.forename: A P A
authors.initials: APA
authors.lastname: Monteiro
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611.
authors.forename: B M
authors.initials: BM
authors.lastname: Ahmed
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611.
authors.forename: G E
authors.initials: GE
authors.lastname: Dahl
mesh_terms: D000818:Animals; D001343:Autophagy; D000071193:Autophagy-Related Protein 7 / Q000235:genetics / Q000378:metabolism; D001831:Body Temperature; D002417:Cattle; D049109:Cell Proliferation; D005260:Female; D005819:Genetic Markers; D018882:Heat Stress Disorders / Q000503:physiopathology* / Q000662:veterinary; D018869:Heat-Shock Response; D006358:Hot Temperature; D006813:Humidity; D007774:Lactation; D008321:Mammary Glands, Animal / Q000166:cytology / Q000503:physiopathology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008892:Milk / Q000378:metabolism; D056152:Respiratory Rate
chemical_list: D005819:Genetic Markers; D008869:Microtubule-Associated Proteins; D000071193:Autophagy-Related Protein 7
keywords: autophagy; dry period; heat stress; mammary gland