Inhibitory Effects Of Phytolacca Esculenta Van Houtte On Pro-inflammatory Cytokines Secretion By Peripheral Blood Mononuclear Cells From Psoriatic Patients And Human Keratinocytes Proliferation In Vitro

Background: Psoriasis is a common, chronic, recurrent, inflammatory proliferative epidermal disease that affects 3 million people in China and 1 % to 3 % of the world's population. The prevalence rate is increasing gradually. Psoriasis vulgaris(PV) is the most common type(99%) characterized by erythematous, dry scaling plaques of various sizes, covered by slivery white and lamellar scales. There does appear to be considerable genetic heterogeneity, and a multifactortial mode of inheritance is most likely. Although the pathogenesis of psoriasis remains unclear, T cell-mediated abnormal immunity attracted particular attention recently. T-cell activation can subsequently result in the production of a variety of cytokines, some of which have been shown to precipitate psoriasis. Overexpression of proinflammatory , type I cytokines has been demonstrated and is believed to be of pathogenic significance in psoriasis. Novel immunotherapies of psoriasis have therefore turned to specifically target the activated T cells directly involved in the development of psoriasis lesions and inhibit their action either directly or through inhibition of pro-inflammatory cytokines secretion or activity[such as Interleukin-2(IL-2) and tumor necrosis factors (TNF- a )].Esculcntoside A (EsA), a kind of purified saponin, and Phytolacca esculenta polysaccharides I (PAP- I ) are the major effective components isolated from the Chinese herb Phytolacca esculenta van Houtte. Recent studies have demonstrated that they both possessed comprehensive pharmacological effects. Satisfactory results with long-lasting remissions were observed in clinical practice when Phytolacca esculenta van Houtte was taken in treating psoriasis. Here we try to elucidate the possible mechanisms for its effectively antipsoriatic use.Objects'. To investigate the effects of EsA and PAP-1 on the expressions of TNF- a and soluble Interleukin-2 receptor (sIL-2R) production in peripheral blood mononuclear cells(PBMC) from patients with PV. To study its anti-proliferative effect on keratinocytes (KC) in vitro that eventually would lead to new therapeutic options for psoriasis.Methods: Whole, heparinized peripheral blood was donated by 30 patients with PV and 20 healthy controls. PBMC were isolated by density centrifugation and stimulated with a mitogen (LPS or PHA) for 24 or 48 hours in the presence or absence of EsA or PAP-1 . The expressions of TNF-a and sIL-2R were assayed by enzyme-linked immunoabsorption assay (ELISA) from the supernatants of cultured PBMC. Skin specimens obtained from healthy children undergoing circumcision were dissociated into single keratinocytes suspensions by trypsin. These different types of cell were co-cultured in serum-free Defined Keratinocyte-SFM medium. Proliferation of KC was assessed by MTT colorimetry.Results'. No matter which culture condition, expressions of TNF- a and sIL-2R were elevated in the patients with psoriasis, compared to the controls. TNF- a was secreted at a significantly decreasing level from psoriatic patients during the concentration of EsA over 1.0 g/mL (P<0.05). And the addition of increasing doses (1.0 g/mL ~ 10.0 g/mL ) of EsA resulted in a dose-dependent inhibition in the expression of TNF- a . Whereas, still significant differences in TNF- a expression were noted between psoriaticand control subjects(P<0.05). sIL-2R decreased slightly, but no statistics difference. PAP-1 , 31~250u g/mL in combination with LPS lOg/mL or PHA 12.5ug/mL was shown to significantly increased the expression of TNF-a and sIL-2R, and the levels of both induced by PAP-1 250 U g/mL reached peaks. While PAP-1 500 g/mL was shown to inhibit the expressions of TNF- a and sIL-2R. Our present results revealed that EsA show no significant inhibition on the proliferation of PBMC induced by PHA. PAP-I ,62.5~500n g/mL alone or in combination with PHA could significantly augment lymphocyte proliferation capability in dosage dependent manner. But, PAP- I 50011 g/mL turned to inhibit the proliferation of PBMC induced by PHA. EsA could directl...