The complete sequencing of the genome of Saccharomyces cerevisiae indicated that this organism contains five genes encoding aldehyde dehydrogenases. YOR374w and YER073w correspond to the mitochondrial isoforms and we propose as gene names ALD4 and ALD5, respectively. YPL061w has been described as the cytoplasmic constitutive isoform and named ALD6. We characterize here the tandem‐repeated ORFs YMR170c and YMR169c as the cytoplasmic stress‐inducible isoforms, with gene names ALD2 and ALD3, respectively. The expression of ALD2 and ALD3 is dependent on the general‐stress transcription factors Msn2,4 but independent of the HOG MAP kinase pathway. ALD3 is induced by a variety of stresses, including osmotic shock, heat shock, glucose exhaustion, oxidative stress and drugs. ALD2 is only induced by osmotic stress and glucose exhaustion. A double null mutant, ald2 ald3, exhibited unchanged sensitivity to any of the above stresses. The only phenotype detected in this mutant was a reduced growth rate in ethanol medium as compared to the wild type. Copyright © 1999 John Wiley & Sons, Ltd.

A locust within chromosome XIII of Saccharomyces cerevisiae containing four genes upregulated by osmotic stress has been characterized. Two of the genes, but not their osmotic induction, were already described: the DNA damage-inducible gene DDR48 and the protease inhibitor gene PAI3. The two novel genes encode a cytoplasmic aldehyde dehydrogenase (ALD2) and a peptide of unknown function (SIP18). These genes form a cluster of two pairs of divergent promoters regulated by osmotic stress. The regulation of the divergent ALD2 and DDR48 genes, however, occurs by different mechanisms. ALD2 exhibits maximum induction with 0.3 M NaCl, negative regulation by protein kinase A and dependence on PBS2 and HOG1 protein kinases for osmotic induction. DDR48 requires 1 M NaCl for maximum induction and its expression in independent of PBS2 and HOG1 protein kinases and less sensitive to protein kinase A. PAI3 and SIP18 are as dependent on the above protein kinases as ALD2. Deletion analysis indicates that most of the regulation of the ALD2 promoter is mediated by a negative element counteracted by osmotic stress.

Our aim was to elucidate the physiological role of calpains (CAPN) in mammary gland involution. Both CAPN-1 and -2 were induced after weaning and its activity increased in isolated mitochondria and lysosomes. CAPN activation within the mitochondria could trigger the release of cytochrome c and other pro-apoptotic factors, whereas in lysosomes it might be essential for tissue remodeling by releasing cathepsins into the cytosol. Immunohistochemical analysis localized CAPNs mainly at the luminal side of alveoli. During weaning, CAPNs translocate to the lysosomes processing membrane proteins. To identify these substrates, lysosomal fractions were treated with recombinant CAPN and cleaved products were identified by 2D-DIGE. The subunit b 2 of the v-type H þ ATPase is proteolyzed and so is the lysosomal-associated membrane protein 2a (LAMP2a). Both proteins are also cleaved in vivo. Furthermore, LAMP2a cleavage was confirmed in vitro by addition of CAPNs to isolated lysosomes and several CAPN inhibitors prevented it. Finally, in vivo inhibition of CAPN1 in 72-h-weaned mice decreased LAMP2a cleavage. Indeed, calpeptin-treated mice showed a substantial delay in tissue remodeling and involution of the mammary gland. These results suggest that CAPNs are responsible for mitochondrial and lysosomal membrane permeabilization, supporting the idea that lysosomal-mediated cell death is a new hallmark of mammary gland involution.

No abstract

Retinoic acid (RA) is a signaling molecule in the morphogenesis of the mammary gland, modulating the expression of matrix metalloproteinases (MMPs). The aim of this paper was to study the role of RA during weaning, which consists of three events: apoptosis of the secretory cells, degradation of the extracellular matrix, and adipogenesis. CRABP II and CRBP-1 carrier proteins increased significantly during weaning compared with lactating glands but reverted to control values after the litter resuckled. The effects of RA are mediated by the nuclear receptors RAR␣, RAR␤, RAR␥, and RXR␣, which underwent an increase in protein levels during weaning. In an attempt to elucidate the RAR␣-dependent signaling pathway, ChIP assays were performed. The results showed the binding of RAR␣ to the MMP-9 promoter after 24-and 72-h weaning together with its coactivator p300; this fact could be responsible for the increase found in MMP-9 mRNA and protein levels in these conditions. Expression of related MMPs (MMP-2 and MMP-3) was also increased during weaning. Using gelatine zymography, we observed a time-dependent increase in active forms of MMP-9 and MMP-2. On the other hand, the inhibitor of MMPs, TIMP-1, was almost undetectable at 24-and 72-h weaning by Western blot. The role of retinoids in matrix remodeling is reinforced by the fact that administration of an acute dose of retinol palmitate to control lactating rats also induces MMP-9 expression. This emphasizes the importance of retinoids in vivo to regulate mammary gland involution. mammary gland involution; matrix metalloproteinase-9; stromelysin-1; retinoic acid; retinoid acid receptor-␣; TO FEMALE MAMMALS, THE COST OF LACTATION is exorbitant compared with other physiological processes. Thus, to assure a good milk production, the lactating animal has developed several physiological changes that include hyperphagia, liver and mammary gland hypertrophy, increased cardiac output, and increased blood flow to the gland, which, together with widespread changes in the metabolism of different tissues, assure a sufficient supply of substrates to the gland for milk production.Few adult tissues exhibit extensive apoptosis under physiological conditions. These include the small intestine, adipose, uterus, ovary, and mammary gland (1, 9). After being weaned, the mammary gland is remodeled in preparation for the next pregnancy/lactation cycle through a complex cellular program.This weaning process has two phases. The first phase is reversible; it depends on p53 and is characterized by the disappearance of the physiological adaptations and by an increase in the number of apoptotic events in the epithelia of the lobulo-alveolar compartment (15, 33). The second phase is p53 independent; it is irreversible and includes a proteolytic degradation of the basement membrane and remodeling of the mammary gland. To achieve the latter events, two main families of extracellular matrix (ECM)-degrading proteinases are activated, matrix metalloproteinases (MMPs) and serine proteinases, that are involved...

At the end of lactation the mammary gland undergoes involution, a process characterized by apoptosis of secretory cells and tissue remodelling. To gain insight into this process, we analysed the gene expression profile by oligonucleotide microarrays during lactation and after forced weaning. Up-regulation of inflammatory mediators and acute-phase response genes during weaning was found. Expression of IκBα (inhibitory κBα), a protein known to modulate NF-κB (nuclear factor-κB) nuclear translocation, was significantly up-regulated. On the other hand, there was a time-dependent degradation of IκBα protein levels in response to weaning, suggesting a role for NF-κB. Furthermore, we have demonstrated, using chromatin immunoprecipitation assays, binding of NF-κB to the NOS-2 (inducible nitric oxide synthase) promoter at the early onset of events triggered during weaning. The three isoforms of NOS are constitutively present in the lactating mammary gland; however, while NOS-2 mRNA and protein levels and, consequently, NO production are increased during weaning, NOS-3 protein levels are diminished. Western blot analyses have demonstrated that protein nitration is increased in the mammary gland during weaning, but this is limited to a few specific tyrosine-nitrated proteins. Interestingly, inhibition of GSH synthesis at the peak of lactation partially mimics these findings, highlighting the role of NO production and GSH depletion during involution.

Liver gamma-cystathionase activity increases in rats during lactation; its inhibition due to propargylglycine is followed by a significant decrease in lactation. This is reversible by N-acetylcysteine administration. To study the role of liver gamma-cystathionase and the intertissue flux of glutathione during lactation, we used lactating and virgin rats fed liquid diets. Virgin rats were divided into two groups as follows: one group was fed daily a diet containing the same amount of protein that was consumed the previous day by lactating rats (high protein diet-fed rats); the other virgin group was fed the normal liquid diet (control). The expression and activity of liver gamma-cystathionase were significantly greater in lactating rats and in high protein diet-fed virgin rats compared with control rats. The total glutathione [reduced glutathione (GSH) + oxidized glutathione (GSSG)] released per gram of liver did not differ in lactating rats or in high protein diet-fed rats, but it was significantly higher in these two groups than in control virgin rats. Liver size and the GSH + GSSG released by total liver were significantly higher in lactating rats than in high protein diet-fed virgin rats, and this difference was similar to the amount of glutathione taken up by the mammary gland (454.2 +/- 36.0 nmol/min). The uptake of total glutathione by the lactating mammary gland was much higher than the uptakes of free L-cysteine and L-cystine, which were negligible. These data suggest that the intertissue flux of glutathione is an important mechanism of L-cysteine delivery to the lactating mammary gland, which lacks gamma-cystathionase activity. This emphasizes the physiologic importance of the increased expression and activity of liver gamma-cystathionase during lactation.

We have investigated the dose (in the range of microM) and time-dependent effects of four different retinoids (retinol, retinal, retinoic acid and retinol palmitate) on human dermal fibroblasts cultivated in vitro. Retinol and retinal, at a concentration of 20 microM, caused cell damage as evaluated by lactate dehydrogenase activity released into the culture medium. The oxidised glutathione (GSSG)/reduced glutathione (GSH) ratio and malondialdehyde production indicated that 20 microM of retinol provoked oxidative stress in the cultivated human fibroblasts. In the first 8 h after retinol treatment the levels of p53 and Bax proteins as well as caspase 3 activity increased, suggesting apoptotic cell death during the first hours of treatment. If the retinol treatment exceeded 18-24 h we observed necrotic cell death. Vitamin E and coenzyme Q(10) had a protective effect against oxidative stress generated by retinol. Both antioxidant molecules reduced retinol uptake, and in the case of vitamin E the expression of CRABP-II mRNA was induced, providing a plausible explanation for its protective effect.