Ginkgo biloba Extract: A Novel Addition to Antipsoriasis Ammunition?

Dear Editor:

Psoriasis is a chronic inflammatory skin disease that affects approximately 2%–4% of the population. ¹ It histologically characterized by epidermal hyperplasia, anomalous keratinocyte differentiation, angiogenesis, and inflammatory cell infiltration. ²

The adhesion of leukocytes and subsequent transmigration through the activated endothelium is one prerequisite for the accumulation of these cells in the psoriasis. ³

Tumour necrosis factor (TNF)-α is a proinflammatory cytokine that can induce antiapoptotic proteins and endothelial cell activation factors in psoriasis. ⁴ Notably, TNF-α is considered the most important cytokine involved in the pathogenesis of psoriasis. ⁵

It has been demonstrated that nuclear factor κB (NF-κB) plays a critical role in immune response inflammation and cell proliferation. ⁶ It merits noting that the NF-κB pathway has been proven to be involved in the progress of psoriasis. ⁷

Interleukin (IL)–6 is produced by both keratinocytes and leukocytes. Elevated levels of IL-6 have been detected in the plasma of patients with psoriasis. IL-6 contributes to the epidermal hyperplasia in psoriatic epithelium and affects the function of dermal inflammatory cells. ⁸

IL-10 is an anti-inflammatory cytokine produced by B- and T-lymphocytes, monocytes, and keratinocytes. It has been observed that IL-10 levels are diminished in psoriatic skin lesions as compared to the normal skin. ⁹

Recent evidence suggests that tissue angiotensin converting enzyme (ACE) activity in altered skin is significantly increased in patients with psoriasis. ¹⁰ Additionally, determination of tissue ACE activity may be a good nonspecific parameter for assessment of therapeutic effects in psoriasis. ¹¹

Notably, it has been suggested that the level of nitric oxide (NO) is increased in patients with psoriasis, and it might play a role in the psoriasis pathogenesis. ¹²

Ginkgo biloba is world's oldest living species of tree. G. biloba originated from China, then was introduced to Japan and Korea centuries ago and subsequently to Europe. ¹³ It has been reported that purified polysaccharide of G. biloba leaves could effectively inhibit the acute inflammation in mice and inhibits P-selectin-mediated leukocyte adhesion in static conditions. ¹⁴

Ilieva and colleagues demonstrated that the anti-inflammatory effect of 1 mg of G. biloba extract (GBE) is as strong as that of the same dose prednisolone, and it significantly reduces the concentration of TNF-α. ¹⁵

Importantly, numerous studies have illustrated that GBE diminishes NF-κB ¹⁶ and IL-6 levels ¹⁷ and elevates the levels of anti-inflammatory cytokine IL-10. ¹⁸

Mansour et al. investigated the potential antihypertensive effect of G. biloba. Interestingly, they demonstrated that it was able to inhibit ACE activity in rat kidney. ¹⁹

Another important point needing attention is that studies have revealed that G. biloba significantly decreases the production of NO. ²⁰

In conclusion, given the ability of G. biloba extract to inhibit P-selectin-leukocyte adhesion, TNF-α, NF-κB, IL-6, ACE, and NO, and also upregulation of anti-inflammatory cytokine IL-10, it could be deduced that G. biloba extract might be effective for psoriasis treatment. Our commentary encourages the conduction of clinical trials on this subject.