Acne vulgaris: physiopathology and cell mechanisms
Acne is a widespread skin condition. It is estimated that 4 out of 5 adolescents will be affected by a more or less severe form of acne during puberty.
According to the severity of the disease, different clinical signs may occur. Acne is generally characterized by the formation of microcomedones, blackheads, papules, pustules and nodules according to severity. If acne mostly affects adolescents, it can also affect adults (pregnant women, middle-aged men) and infants. Clinical signs are often limited to the face but may also be found on the neck, upper back, chest, lower arms and shoulders. There is currently no effective treatment for acne but most cases are mild and clear up spontaneously.
Dysregulation of the proliferation process of follicular keratinocytes
Dysregulation of the proliferation process of follicular keratinocytes is another characteristic of acne. It results in the formation of comedones at the level of the excretory duct of the pilosebaceous unit and in pore obstruction [Assay: NHEK-0053].
Activation of inflammatory response
Alteration of sebum composition
Comparative studies between the sebum of healthy individuals and that of individuals affected with acne have shown a qualitative and quantitative difference in composition.
Squalene is a lipid compound which is characteristic of sebum. During cholesterol synthesis, squalene is an intermediary compound which is sensitive to oxidation reactions such as peroxidation. During peroxidation, squalene can generate compounds with an adverse effect on cells, such as reactive oxygen species, which will cause the stimulation of inflammatory response. Malfunctioning of squalene metabolism reactions, via for example enzyme squalene epoxidase, can lead to squalene accumulation. This increase of squalene availability in sebum results in an increase of peroxidation reactions, via UV rays in particular, and thus causes an increase of the quantity of reactive oxygen species (responsible for the activation of inflammatory response).
As the body’s protective barrier, skin is constantly exposed to air pollution damage. Air pollution, which is the result of urbanization and industrialization, is constituted of fine particles, which stimulate sebum production and so lead to an exacerbation of acne (to find out more about this, see article: Effects of different kinds of pollutants on the lipidic metabolism of human sebocytes and protective effects of a new macroalgae culture extract).