Association between smoking and hair loss: another opportunity for health education against smoking?

Besides being the single most preventable cause of significant morbidity and an important cause of death in the general population, tobacco smoking has been associated with adverse effects on the skin. Smoke-induced premature skin ageing has attracted the attention of the medical community, while only recently an observational study has indicated a significant relationship between smoking and baldness. The mechanisms by which smoking causes hair loss are multifactorial and are probably related to effects of cigarette smoke on the microvasculature of the dermal hair papilla, smoke genotoxicants causing damage to DNA of the hair follicle, smoke-induced imbalance in the follicular protease/antiprotease systems controlling tissue remodeling during the hair growth cycle, pro-oxidant effects of smoking leading to the release of pro-inflammatory cytokines resulting in follicular micro-inflammation and fibrosis and finally increased hydroxylation of oestradiol as well as inhibition of the enzyme aromatase creating a relative hypo-oestrogenic state. In view of the psychological impact of androgenetic alopecia on affected men and women, increasing public awareness of the association between smoking and hair loss offers an opportunity for health education against smoking that may be more effective than the link between smoking and facial wrinkles or grey hair, since the latter can be effectively counteracted by current aesthetic dermatologic procedures, while treatment options for androgenetic alopecia are limited.

Age-associated decreases in human DNA repair capacity: Implications for the skin

Multiple pathways are involved in accurate synthesis and distribution of DNA during replication, repair and maintenance of genomic integrity. An increased error rate, abovethe spontaneous mutation baseline, has been implicated in carcinogenesis and aging. Moreover, cytogenetic abnormalities are increased in Down's, Edwards', Patau's, and Klinefelter's syndromes with increasing maternal age, and in Marfan's and Apert's syndromes with paternal age. In response to DNA damage, multiple overlapping systems of DNA repair have evolved, preferentially repairing the transcribed strand within transcriptionally-active regions of the genome. These include direct reversal of dimers and specific adducts and pathways for base excision, nucleotide excision, and mismatch repair. A consensus has emerged that some DNA repair capacities decline with organism age, contradictory reports notwithstanding. As is the case for inborn defects in humans, knockout mice lacking components of nucleotide excision repair or DNA-damage checkpoint arrest have increased frequencies of skin and internal cancers, whereas mice overexpressing DNA repair genes have fewer spontaneous cancers. Oxidative stress and resultant free radicals can damage genomic and mitochondrial DNA; damage increases with age but decreases with caloric restriction. We review recent studies of long-lived C. elegans mutants which appear to involve metabolic attenuation, the role of telomere shortening and telomerase in cellular senescence, and the genetic bases of progeroid syndromes in humans. Finally, we discuss roles of extrinsic and intrinsic factors in skin aging, and their association with DNA damage, emphasizing preventive and protective measures and prospects for intervention by modulating DNA repair pathways in the skin.