Repeated exposure of human skin fibroblasts to UVB at subcytotoxic level triggers premature senescence through the TGF-beta1 signaling pathway.

Premature senescence of human diploid fibroblasts (HDFs) can be induced by exposures to a variety of oxidative stress and DNA damaging agents. In this study we developed a robust model of UVB-induced premature senescence of skin HDFs. After a series of 10 subcytotoxic (non-proapoptotic) exposures to UVB at 250 mJ/cm2, the so-called biomarkers of senescence were markedly expressed: growth arrest, senescence-associated beta-galactosidase activity, senescence-associated gene overexpression, deletion in mitochondrial DNA.

Role of the PLA2-independent peroxiredoxin VI activity in the survival of immortalized fibroblasts exposed to cytotoxic oxidative stress.

Peroxiredoxin VI (PrxVI) is a bifunctional enzyme with non-selenium glutathione peroxidase and Ca2+-independent acidic phospholipase A2 activities. We demonstrate that transfection-mediated PrxVI overexpression protects immortalized human WI-38 and murine NIH3T3 fibroblasts against cytotoxic doses of tert-butylhydroperoxide and H2O2. Mutants for either glutathione peroxidase or phospholipase A2 activity show that glutathione peroxidase but not phospholipase A2 activity is required to promote cell survival after stress.

Stress-induced premature senescence and replicative senescence are different phenotypes, proteomic evidence.

In this paper, we illustrate how a proteomic analysis can be useful to approach complex biological problems, in this case the concept of stress-induced premature senescence (SIPS). According to the stochastic theories of ageing, damage that accumulate with time in the cellular components are responsible for cellular ageing. As a corollary, some sort of premature senescence should appear if the damage level is artificially increased due to the presence of stressing agents at subcytotoxic level.

UVB-induced premature senescence of human diploid skin fibroblasts.

In this work, we show that repeated stresses with UVB (290-320 nm) induce stress-induced premature senescence (SIPS) of skin human diploid fibroblasts (HDFs). HDFs at early cumulative population doublings were exposed three or five times to increasing subcytotoxic doses of UVB with one stress per day. After 2 days of recovery, several biomarkers of replicative senescence were established.

Overexpression of apolipoprotein J in human fibroblasts protects against cytotoxicity and premature senescence induced by ethanol and tert-butylhydroperoxide.

Human diploid fibroblasts (HDFs) exposed to subcytotoxic stresses under H2O2, tert-butylhydroperoxide (t-BHP), and ethanol (EtOH) undergo stress-induced premature senescence (SIPS) characterized by many biomarkers of HDFs replicative senescence. Among these biomarkers are a growth arrest, an increase in the senescence-associated beta-galactosidase activity, a senescent morphology, an overexpression of p21waf-1 and the subsequent inability to phosphorylate pRb, the presence of the common 4977-bp mitochondrial deletion, and an increase in the steady-state level of several senescence-associated genes such as apolipoprotein J (apo J). Apo J has been described as a survival gene against cytotoxic stress.

Identification of the phospholipase A(2) isoforms that contribute to arachidonic acid release in hypoxic endothelial cells: limits of phospholipase A(2) inhibitors.

Changes in endothelium functions during ischemia are thought to be of importance in numerous pathological conditions, with, for instance, an increase in the release of inflammatory mediators like prostaglandins. Here, we showed that hypoxia increases phospholipase A(2) (PLA(2)) activity in human umbilical vein endothelial cells. Both basal PLA(2) activity and PG synthesis are sensitive to BEL and AACOCF3, respectively, inhibitors of calcium-independent PLA(2) (iPLA(2)) and cytosolic PLA(2) (cPLA(2)), while OPC, an inhibitor of soluble PLA(2) (sPLA(2)) only inhibited the hypoxia-induced AA release and PGF(2alpha) synthesis.