Tight Junction Protein Abundance and Apoptosis During Involution of Rat Mammary Glands.
To examine tight junction protein abundance and apoptosis of epithelial cells at the onset of involution in rodent mammary glands, milk accumulation and mammary engorgement were induced by teat-sealing with an adhesive for 0, 6, 12, 18, 24, and 36 h (n = 6 per group) at peak lactation. In non-sealed control glands, histological analysis confirmed a lactating phenotype, indicating suckling by pups throughout the experiment. In contrast, alveoli of teat-sealed glands were distended within 6 h, with maximal luminal size observed by 12 h of non-suckling. By 18 h following teat-sealing, an involuting phenotype was observed, indicated by alveolar lumina engorged with milk vesicles and increased leukocytes. Relative to non-sealed glands, mammary apoptosis was increased in engorged glands 18 h following teat-sealing. The abundance of ZO-1 and occludin proteins was decreased in engorged glands by 12 and 18 h, respectively, following teat-sealing. In contrast, the claudin-1 22 kDa band was increased by 6 h and peaked at 12-18 h, whereas the 28 kDa band declined by 36 h, relative to controls. There were no temporal changes in ZO-1, occludin, and claudin-1 22 kDa proteins within control glands, although there were minor differences in claudin-1 28 kDa. These data indicate that intramammary milk accumulation due to cessation of milk removal is associated with mammary apoptosis. The apoptotic event is preceded by a rapid loss of abundance of ZO-1, occludin and an initial increase in claudin-1. The loss of cell-cell communication may initiate involution and apoptosis of mammary epithelial cells and is a localized intramammary event, occurring only in non-suckled glands. J. Cell. Physiol. 232: 2075-2082, 2017. © 2016 Wiley Periodicals, Inc.
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|DairyNZ Ltd., Hamilton, New Zealand.
Claire V C
CVC
Phyn
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|SciLactis Ltd., Hamilton, New Zealand.
Kerst
K
Stelwagen
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|LIC, Hamilton, New Zealand.
Stephen R
SR
Davis
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|ManukaMed Ltd., Hamilton, New Zealand.
Christopher D
CD
McMahon
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|Carne Technologies Ltd., Cambridge, New Zealand.
Joanne M
JM
Dobson
AgResearch Ltd., Ruakura Research Centre, Hamilton, New Zealand.|Science Consultancy, Hamilton, New Zealand.
Kuljeet
K
Singh
D000818:Animals; D017209:Apoptosis; D062445:Claudin-1 / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism* / Q000473:pathology; D062793:Occludin / Q000378:metabolism; D010641:Phenotype; D011247:Pregnancy; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D062725:Tight Junction Proteins / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors; D014886:Weaning; D062826:Zonula Occludens-1 Protein / Q000378:metabolism
D062445:Claudin-1; C568114:Cldn1 protein, rat; D062793:Occludin; C568987:Ocln protein, rat; D062725:Tight Junction Proteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein