Carmen Domínguez-Jiménez

Photoprotective properties of a hydrophilic extract of the fern Polypodium leucotomos on human skin cells

The effect of a hydrophilic extract of the fern Polypodium leucotomos (PLE) has been investigated in terms of photoprotection against UV-induced cell damage. PLE efficiently preserved human fibroblast survival and restored their proliferative capability when the cells were exposed to UVA light. This effect was specific and dose-dependent. Photoprotection was not restricted to fibroblasts, as demonstrated by its effect on survival and proliferation of the human keratinocyte cell line HaCat. Finally, treatment of the cells with PLE prevented UV-induced morphological changes in human fibroblasts, namely disorganisation of F-actin-based cytoskeletal structures, coalescence of the tubulin cytoskeleton and mislocalization of adhesion molecules such as cadherins and integrins. Our in vitro results demonstrate the photoprotective effect of PLE on human cells and support its use in the preventive treatment of sunburning and skin pathologies associated with UV-mediated damage.

Interleukin-15 and interferon-γ participate in the cross-talk between natural killer and monocytic cells required for tumour necrosis factor production

We have characterized the lymphocyte subset and the receptor molecules involved in inducing the secretion of TNF by monocytic cells in vitro. The TNF secreted by monocytic cells was measured when they were co-cultured with either resting or IL-15-stimulated lymphocytes, T cells, B cells or natural killer (NK) cells isolated from the peripheral blood of healthy subjects and from the synovial fluid from patients with inflammatory arthropathies. Co-culture with IL-15-activated peripheral blood or synovial fluid lymphocytes induced TNF production by monocytic cells within 24 hours, an effect that was mainly mediated by NK cells. In turn, monocytic cells induced CD69 expression and IFN-γ production in NK cells, an effect that was mediated mainly by β2 integrins and membrane-bound IL-15. Furthermore, IFN-γ increased the production of membrane-bound IL-15 in monocytic cells. Blockade of β2 integrins and membrane-bound IL-15 inhibited TNF production, whereas TNF synthesis increased in the presence of anti-CD48 and anti-CD244 (2B4) monoclonal antibodies. All these findings suggest that the cross-talk between NK cells and monocytes results in the sustained stimulation of TNF production. This phenomenon might be important in the pathogenesis of conditions such as rheumatoid arthritis in which the synthesis of TNF is enhanced.

Inhibition of TNF and IL-17 production by leflunomide involves the JAK/STAT pathway

Objective: To study the effects of different disease-modifying antirheumatic drugs (DMARD) on different events mediated by IL-15-activated lymphocytes. Methods: Peripheral blood lymphocytes (PBL) were isolated from healthy donors and activated with IL-15 after exposure to different DMARD: leflunomide, cyclosporin A, methotrexate, mycophenolic acid, FK-506, sulphasalazine and sodium aurothiomalate. The expression of different surface molecules on the PBL was then determined by flow cytometry. Cells were also co-cultured with the monocytic cell line THP-1 and the tumour necrosis factor (TNF) concentration in the supernatant was measured after 24 h using an immunoenzyme assay. The effect of the aforementioned drugs on IL-17 production by IL-15-activated PBL was also studied. Results: Treatment of PBL with leflunomide, cyclosporin A and FK-506 inhibited the IL-15-induced expression of both CD54 and CD69 by PBL, as well as TNF production in co-cultures of activated PBL and THP-1 cells. The downregulation of CD54 and CD69 in PBL was correlated with the inhibition of TNF production. Likewise, leflunomide, cyclosporin A and FK-506 all inhibited IL-17 production in IL-15-activated PBL. Interestingly, the effect of leflunomide was not reverted by the presence of uridine in the medium. In addition, leflunomide inhibited the phosphorylation of STAT6 in vitro. Conclusion: Inhibition of the JAK/STAT pathway may represent an additional effect of leflunomide in chronic polyarthritis because it impairs certain events that control proinflammatory TNF and IL-17 cytokine production.

Involvement of α3 integrin/tetraspanin complexes in the angiogenic response induced by angiotensin II

The effect of angiotensin II (Ang II) on endothelial cell (EC) function has important potential implications, both under physiological conditions and in the pathogenesis of different cardiovascular diseases. We studied the effect of Ang II on EC junctions and its possible functional consequences. We found that Ang II induced a remarkable change on human umbilical vein endothelial cells (HUVEC) in the distribution of α3β1 integrin and CD151, CD9 tetraspanins on cell membrane, with an important decrease of these molecular complexes at intercellular contacts. However, the morphology of EC, the integrins located at cell‐substratum contact areas, the components of adherens and tight‐junctions, as well as the barrier functions of EC monolayers, remained unchanged after Ang II exposure. The Ang II effect on α3β1 1/tetraspanins complexes was associated with a significant induction of angiotube formation by HUVEC in an in vitro model of capillary formation on Matrigel. The effect of Ang II was mediated through the angiotensin II receptor 1 AT1 receptor and was inhibited with antibodies specific for the α3 integrin chain, which indicates the critical role of this integrin in the angiogenic effect of Ang II. These results show that Ang II exerts a direct and very specific effect on EC lateral junctions that is selectively associated with the induction of angiogenesis by this peptide.

Prevention of αIIbβ3 activation by non-steroidal antiinflammatory drugs

We have studied the effect of non‐steroidal antiinflammatory drugs (NSAIDs) on αIIbβ3 integrin activation and platelet aggregation. NSAIDs such as meloxicam, piroxicam, indomethacin and aspirin, but not aceclofenac or diclofenac interfered with the activation state of αIIbβ3. NSAIDs that inhibited αIIbβ3 activation were also able both to partially inhibit platelet primary aggregation and to accelerate platelet deaggregation. These effects of NSAIDs were not dependent on cyclooxygenase inhibition. The results obtained indicate that some NSAIDs exert a specific action on αIIbβ3 activation, and provide an additional mechanism that accounts for their beneficial effects in diseases in which platelet activation is involved.