Augmented glucose-6-phosphate dehydrogenase activity and normal penetration and metabolism of dehydroepiandrosterone in mononuclear leukocytes in psoriasis

DHEA prevents ribavirin-induced anemia via inhibition of glucose-6-phosphate dehydrogenase

Ribavirin has been widely used for antiviral therapy. Unfortunately, ribavirin-induced anemia is often a cause of limiting or interrupting treatment. Our team has observed that dehydroepiandrosterone (DHEA) has a protective effect against in vitro and in vivo ribavirin-induced hemolysis. The aim of this study was to better understand this effect as well as the underlying mechanism(s). DHEA was able to reduce in vitro intraerythrocytic ATP depletion induced by ribavirin. Only 1% of ATP remained after incubation with ribavirin (2 mM) at 37 °C for 24 h vs. 37% if DHEA (200 μM) was added (p < 0.01). DHEA also helped erythrocytes conserve their size, with a shrinkage of only 10% vs 40% at 24 h with ribavirin alone (p < 0.01), and reduced phosphatidylserine exposure at the outer membrane, i.e. 27% vs 40% at 48 h, (p < 0.05). DHEA also inhibits ribavirin-induced hemolysis, i.e. 34% vs 46.5% at 72 h (p < 0.01). DHEA is an inhibitor of glucose-6-phosphate dehydrogenase (G6PD), a key enzyme in the hexose monophosphate shunt connected to the glycolytic pathway which is the only energy supplier of the red blood cell in the form of ATP. We have confirmed this inhibitory effect in the presence of ribavirin. All these observations suggest that ribavirin-induced hemolysis was initiated by ATP depletion, and that the inhibitory effect of DHEA on G6PD was able to rescue enough ATP to limit this hemolysis. This mechanism could be important for improving the therapeutic management of patients treated with ribavirin.

A highly decreased binding of cyclic adenosine monophosphate to protein kinase A in erythrocyte membranes is specific for active psoriasis

A cyclic adenosine monophosphate binding abnormality in psoriatic erythrocytes that could be corrected by retinoid treatment has been reported. It was tested whether this binding abnormality is specific for psoriasis and the effects of treatment were compared with etretinate, cyclosporine A, or anthralin on 2-(3)H-8-N(3)-cyclic adenosine monophosphate binding to the regulatory subunit of protein kinase A in erythrocyte membranes. One hundred and fifteen individuals were evaluated, including: (i) 34 healthy persons; (ii) 15 patients with nonatopic inflammatory skin diseases (eczema, erythroderma, tinea, Grover's disease, erysipelas, urticaria); (iii) eight with other dermatoses mediated by immune mechanisms (systemic lupus erythematosus, lichen planus, necrotizing vasculitis, erythema nodosum, systemic sclerosis); (iv) 14 with generalized atopic dermatitis; and (v) 44 with psoriasis vulgaris clinically assessed by Psoriasis Area and Severity Index. In psoriasis, the course of the binding of 2-(3)H-8-N(3)-cyclic adenosine monophosphate to erythrocytes was measured in nine patients during a 10 wk treatment with etretinate, in 21 patients during a 10 wk treatment with cyclosporine A, and one patient under topical treatment with anthralin for 4 wk. We found the following femtomolar binding per mg protein: (i) healthy persons (1064 +/- 124, mean +/- SD); (ii) nonatopic inflammatory skin diseases (995 +/- 103); (iii) immune dermatoses (961 +/- 92); (iv) atopic dermatitis (960 +/- 110); and (v) psoriasis (645 +/- 159; p < 0.0001 compared with nonpsoriatics, Mann-Whitney U test). Treatment of psoriasis with etretinate, cyclosporine A, or anthralin normalized the binding of cyclic adenosine monophosphate, which was inversely correlated to the Psoriasis Area and Severity Index score. It was concluded that the decreased binding of cyclic adenosine monophosphate to protein kinase A in erythrocytes is specific for psoriasis and normalizes after successful treatment.

Enhanced procoagulant activity of mononuclear leukocytes in patients with atopic dermatitis and psoriasis

Fibrin deposition is an important histopathological feature of inflammatory skin lesions and is mediated in part, by procoagulants generated by mononuclear leucocytes (MNL). We examined whether MNL from patients with atopic dermatitis or psoriasis generate enhanced procoagulant activity (PCA). MNL isolated from the peripheral blood of 15 healthy control individuals, 15 patients with atopic dermatitis and 15 patients with psoriasis were incubated for 24 h in the presence or absence of bacterial lipopolysaccharide (LPS). MNL or the cell culture supernatants were then added to recalcified human plasma to determine the clotting time. We found that in both atopic dermatitis and psoriasis MNL cultured in the presence or absence of LPS expressed greatly enhanced PCA (p < 0.01 to < 0.002). Supernatants from MNL cultures from patients with psoriasis, but not those from patients with atopic dermatitis, also generated augmented PCA (p < 0.002). In psoriasis, PCA normalized after successful topical treatment with anthralin. We conclude that enhanced PCA is a characteristic feature of MNL in both atopic dermatitis and psoriasis. In psoriasis the enhanced PCA is directly related to disease activity.

Stimulation of T cells by autologous mononuclear leukocytes and epidermal cells in psoriasis

Based on reports suggesting aberrant cell-mediated immunity and altered infiltration of immunocompetent cells into the skin in psoriasis, we studied the stimulation of T cells by autologous non-T mononuclear leukocytes (autologous mixed lymphocyte reaction, AMLR) and by epidermal cells isolated from lesional and clinically uninvolved skin in psoriasis (autologous mixed epidermal cell lymphocyte reaction, AMECLR). Age- and sex-matched individuals served as controls. We found that the AMLR in psoriasis (n = 11) was similar to that in healthy controls (n = 16); furthermore, cell proliferation was alike in the presence of either 5% AB-serum or autologous serum. By contrast, while the AMECLR in healthy controls (n = 9) resembled that in psoriatics employing epidermal cells from univolved skin, epidermal cells from lesional sites (n = 10) induced a significantly higher proliferation of autologous T cells in the AMECLR (P less than 0.01). We conclude that the in vitro stimulation of T cells by non-T mononuclear leukocytes is normal in psoriasis and is not regulated by autologous serum. Lesional psoriatic epidermal cells, however, are more active in stimulating autologous T cell proliferation than cells from univolved psoriatic or normal epidermis.