Dermatology Online Journal

Prostaglandin analogs for hair growth: Greater expectations
M R Namazi MD
Dermatology Online Journal 9 (5): 29

From the Dermatology Department, Shiraz University of Medical Sciences, Shiraz, Iran. namazi_mr@yahoo.com

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An interesting paper has recently appeared in Dermatology Online Journal that introduced prostaglandin analogs as nonspecific stimulators of hair growth and predicted their use as the next agents for treatment of forms of alopecia [1]. Prostaglandin analogs not only may stimulate human hair growth, but also may exert an inhibitory effect on the pathomechanism behind alopecia areata (AA) and therefore could be invaluable agents for this condition.

The exact mechanism underlying the pathology of AA is currently unknown, although it is believed to be an autoimmune disorder. Increased expression of ICAM-1 and MHC class II molecules (such as HLA-DR on follicular epithelial cells) and also intense expression of E-selectin, VCAM-1, and ICAM-1 on the perifollicular dermal vessels are demonstrated in this condition [2].

Several observations suggest the involvement of TH1-type cytokines in inflammatory responses observed in AA. For example, IFN-γ and TNF-α have been shown to participate in the pathology of AA. In patients with AA, a TH2 cytokine profile may indicate a good prognostic value; a TH1 cytokine profile appears to indicate a poor prognosis [2].

Prostaglandin E2 (PGE2) increases intracellular cAMP levels and has important immunoregulatory functions. It exerts a suppressive effect on macrophage functions such as antigen presentation and MHC class II expression [3, 4]. It also decreases the proliferation of TH1 cells and expression or synthesis of the TH1 cytokines, IL-1, IL-2, IFN-γ, and TNF-α, and it increases the production of IL-4, which counterregulates the effects of type 1 cytokines [4]. Although PGE2 inhibits the production of TH1 lymphokines, it does not inhibit that of Th2 lymphokines and its production by macrophages explains why presentation of antigens by these cells leads to generation of Th2 cells. Whereas B cells, which do not produce PGE2, induce generation of TH1 cells [5].

Therefore, PGE2 suppresses cellular immune response generated by TH1 cells. An illustration of this process is the depression of cellular immunity following hemorrhage and burns, a depression that is associated with overproduction of PGE2 and is inhibited by ibuprofen [4].

Given that PGE2 exerts an inhibitory influence on type 1 immune response, which is the underlying immunopathology of AA, PGE2 analogs may prove to be invaluable in the treatment of this clinical conundrum.

References

1. Wolf R, Matz H, Zalish M, Pollack A, Orion E. Prostaglandin analogs for hair growth: Great expectations. Dermatol Online J 2003; 9(3): 7.

2. Namazi MR. Nitric oxide donors as potential additions to anti-alopecia areata armamentarium. Inflam Res 2003; 52: 227-9.

3. Etrel W, Morrison MH, Meldrum DR, Ayala A, Chaudry IH. Ibuprofen restores cellular immunity and decreases susceptibility to sepsis following hemorrhage. J Surg Res 1992; 53: 55-61.

4. Namazi MR. Why is psoriasis uncommon in Africans? The influence of dietary factors on the expression of psoriasis (In Press).

5. Betz M, Fox BS. Prostaglandin E2 inhibits production of TH1 lymphokines but not of Th2 lymphokines. J Immunol 1991; 146(1): 108-13.

© 2003 Dermatology Online Journal