Pregnancy-specific glycoproteins (PSGs) comprise a family of highly similar polypeptides encoded by 11 transcriptionally active genes that compactly cluster on band 19q13.2. All members of the PSG family were found to be markedly up-regulated by addition of 5-bromodeoxyuridine in HeLa cells. Similarly, all of the members were markedly up-regulated during replicative senescence in normal human fibroblasts. Promoter analysis of the PSG1, 4, and 11 genes in HeLa cells did not reveal a cis-regulatory element responsive to 5-bromodeoxyuridine in their 5'-flanking sequences. These results suggest that the PSG genes are regulated at a level of higher order chromatin structure besides by a signal of pregnancy.

Cell swelling and retardation in DNA replication are always observed in senescent cells. When DNA replication is slowed down with RNA and protein syntheses unchanged in proliferating cells, it causes a phenomenon known as unbalanced growth. The purpose of this study is to assess the role of cell swelling in unbalanced growth in terms of senescence and investigate the mechanism underlying this phenomenon. We tried to induce cell swelling with minimum damage to cells in this study. We perturbed the osmoregulatory functions to induce cell swelling under hypotonic and hypertonic conditions in normal human fibroblasts. Addition of excess NaCl was found to induce significant cell and nuclear swelling in dose- and time-dependent manners. Excess NaCl immediately retarded DNA replication, accumulated cells at G1 phase of the cell cycle, and eventually deprived division potential of the cells. Such cells showed typical senescent cell shape followed by expression of the typical senescence-associated genes. Excess NaCl also activated ERK1/2, p38, and JNK of the mitogen activated protein kinase family. Addition of U0126, an inhibitor of ERK1/2, prevented appearance of senescent features induced by excess NaCl. These results suggest that hypertonic conditions induce cell swelling due to unbalanced growth, thereby leading to cellular senescence.

Background Cellular senescence, a phenomenon of irreversible growth arrest of mammalian cells, is involved in various age‐related phenomena in organisms. Hair follicle dermal papilla (DP) cells play important roles in the regulation of hair growth and loss. Aims We examined the implication of cellular senescence of DP cells in androgenetic alopecia (AGA), the most common form of male hair loss, and searched for the compounds that have a beneficial effect on the prevention of AGA. Patients/Methods Expression of the 5α‐reductase type II (SRD5A2) gene, which plays a key role in the development of AGA, was examined by quantitative RT‐PCR and Western blotting analysis in DP cells. Besides, DP cells were cultured with the extracts of herbs used in traditional Ayurvedic medicine to search for the compounds that have a beneficial effect on the growth of DP cells. Results We found that expression of the SRD5A2 was up‐regulated in senescent DP cells. We also found that the herbal extract of Plumbago zeylanica (root) enhanced the growth of DP cells and down‐regulated the expression of SRD5A2 in DP cells. Further, plumbagin, an ingredient of P zeylanica, would be responsible for the above effects of P zeylanica. Conclusion These results suggested the possibility that senescent DP cells may have a role in the development of AGA through up‐regulating SRD5A2 expression, and the P zeylanica extract and plumbagin may suppress its development through enhancing the growth of DP cells and down‐regulating SRD5A2 expression in DP cells.

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Sublethal doses of surfactants as exemplified by NP-40 clearly induce premature senescence in normal human cells. To understand molecular basis for this phenomenon, we tried to suppress it with use of various inhibitors. An inhibitor of p38 of the MAPK family almost completely suppressed growth arrest and morphological changes induced by surfactants; however, other inhibitors tested had no effect. Oleic acid, a weak inducer of premature senescence, was found to suppress the effect of NP-40. Fluorescein-labeled oleic acid rapidly bound to the cell surface, and this binding was clearly blocked by pre-treatment with surfactants, suggesting that surfactants and oleic acid compete for binding to the cell surface. Moderate concentrations of cycloheximide, an inhibitor of protein synthesis, also suppressed the senescent features induced by NP-40. These results suggest that surfactants activate p38 signaling pathway by binding to the cell surface, and induce cellular senescence.