Anti-inflammatory activity of Lychnophora passerina, Asteraceae (Brazilian "Arnica")

ETHNOPHARMACOLOGICAL RELEVANCE

Lychnophora passerina (Asteraceae), popularly known as "arnica," is used to treat inflammation, pain, rheumatism, contusions, bruises and insect bites in Brazilian traditional medicine.

MATERIALS AND METHODS

The anti-inflammatory activity of crude ethanolic extract of aerial parts of L. passerina and its ethyl acetate and methanolic fractions had their abilities to modulate the production of NO, TNF-α and IL-10 inflammatory mediators in LPS/IFN-γ-stimulated J774.A1 macrophages evaluated. Moreover, the crude ethanolic extract and derived fractions were also in vivo assayed by carrageenan-induced paw oedema in mice.

RESULTS

In vitro assays showed remarkable anti-inflammatory activity of L. passerina crude ethanolic extract (EE) and its ethyl acetate (A) and methanolic (M) fractions, through the inhibition of production of NO and TNF-α inflammatory mediators and induction of production of IL-10 anti-inflammatory cytokine. In vivo assays showed anti-inflammatory activity for EE 10% ointment, similar to the standard drug diclofenac gel. The A and M fraction ointments 20% presented anti-inflammatory activity.

CONCLUSION

The results obtained showed that possible anti-inflammatory effects of EE and its A and M fractions may be attributed to inhibition pro-inflammatory cytokines production, TNF-α and NO and to increased IL-10 production. EE, A and M ointments showed topical in vivo anti-inflammatory activity. The in vivo anti-inflammatory activity of EE of L. passerina may be related to synergistic effects of different substances in the crude extract. Therefore, traditional use of aerial parts of L. passerina in the inflammatory conditions could be beneficial to treat topical inflammatory conditions, as evidenced by the present study.

Nitric oxide-mediated immune complex-induced prostaglandin E(2) production by peripheral blood mononuclear cells of humans infected with Schistosoma mansoni

Granuloma reaction around Schistosoma mansoni eggs is the prominent lesion in human schistosomiasis. Studies have suggested the involvement of a series of suppressive mechanisms in the control of this reaction. Using an in vitro model of granuloma formation, we have shown that immune complexes (IC) isolated from sera of chronic intestinal schistosomiasis patients were able to reduce granulomatous reaction developed against soluble egg antigen-conjugated polyacrylamide beads. In this system, the role of the l-arginine-nitric oxide (NO) pathway in the formation of prostaglandin E(2) (PGE(2)) by human peripheral blood mononuclear cells (PBMC) of patients infected with schistosomiasis was investigated using IC. Preincubation of PBMC with IC produced a significant increase of both nitrite and PGE(2) levels in the cell supernatant. This effect was inhibited by coincubation of cells with Nomega-nitro-l-arginine methyl ester (L-NAME), a NO synthase inhibitor, showing that the release of PGE(2) subsequent to IC stimulation was driven by NO. The inhibitory effect of L-NAME on PGE(2) release by IC-treated PBMC was reversed by sodium nitroprusside, a known NO donor. Our results indicate that NO could be an important second signal for the stimulation of PGE(2) production induced by IC in PBMC from human schistosomiasis patients.

Down modulation of MHC surface molecules on B cells by suppressive immune complexes obtained from chronic intestinal schistosomiasis patients

Granulomatous inflammation around parasite eggs is the prominent lesion in human schistosomiasis. Studies have suggested the involvement of a series of suppressive mechanisms in the control of this reaction, such as macrophages, cytokines, idiotypic interactions and immune complexes (IC). The studies examine the role of IC obtained from chronic intestinal schistosomiasis patients (ISP) in the reactivity of peripheral blood mononuclear cells (PBMC). The results have shown that these immune complexes are able to suppress cell reactivity by inducing an increase in the production of soluble mediators such as prostaglandins and IL-10. To gain a better understanding of how this suppression occurs the present study examines the phenotypic pattern of PBMC after immune complex treatment in cell proliferation assays. These data show that cultures including immune complex present a higher percentage of B lymphocytes in which a lower expression of a MHC-class II gene product, HLA-DR was detected. This altered expression of the HLA-DR molecule on B lymphocytes after IC treatment suggests a novel mechanism for the suppression observed, that is, IC might decrease the antigen-presenting function of B lymphocytes.

Role of immune complexes from patients with different clinical forms of schistosomiasis in the modulation of in vitro granuloma research

Schistosomiasis is a disease whose pathology is strongly related to the granulomatous reaction formed around parasite eggs trapped in host tissues. Studies have shown that the chronic intestinal form (INT) of this infection is associated with a variety of immunoregulatory mechanisms which lead to a diminished granulomatous reaction. Using an in vitro model of granuloma reaction, we show that immune complexes (IC) isolated from sera of INT patients are able to reduce granulomatous reaction developed by peripheral blood mononuclear cells (PBMC) from acute (AC), INT and hepatosplenic (HE) patients to soluble egg antigen (SEA)-conjugated polyacrylamide beads (PB-SEA). This inhibitory activity is also observed in cell proliferation assay of PBMC from INT and HE patients stimulated with SEA and adult worm antigen (SWAP). Furthermore, IC isolated from sera of patients with different clinical forms of the disease are also able to suppress INT patients PBMC reactivity. Therefore, our results show that circulating IC present in sera of patients with different clinical forms of schistosomiasis may downregulate PBMC reactivity to parasite antigens resulting in a diminished granuloma reaction to parasite eggs.

Mice lacking the gamma interferon receptor have an impaired granulomatous reaction to Schistosoma mansoni infection

The egg-induced granulomatous reaction in Schistosoma mansoni-infected individuals develops within the portal system of the liver and is the major pathological finding in schistosomiasis. We have infected mice lacking the gamma interferon (IFN-gamma) receptor with S. mansoni larvae and studied the development of hepatic granulomas in these mutant mice in comparison to that in control wild-type mice. In the absence of IFN-gamma activity, a dramatic reduction in the size and architecture of the granuloma was observed. Granulomas from mutant mice were smaller than those from the control group and showed a significant reduction in the number of infiltrating inflammatory cells. Moreover, they appear to prematurely progress to the chronic phase of the reaction at a time when the control group still has acute inflammation. Our data suggests a pivotal role for IFN-gamma in the early events of the granulomatous reaction in vivo.

IL-10 plays a role in the modulation of human granulomatous hypersensitivity against Schistosoma mansoni eggs induced by immune complexes

It has been demonstrated that the chronic intestinal form of schistosomiasis is associated with the establishment and maintenance of a variety of immunoregulatory mechanisms that lead to a diminished granulomatous reaction to parasite eggs. Using an in vitro model of granuloma reaction we showed that immune complexes (IC) isolated from the sera of chronic intestinal schistosomiasis patients were able to reduce the granulomatous hypersensitivity (developed by peripheral blood mononuclear cells (PBMC) from schistosomiasis patients) to soluble egg antigen (SEA)-conjugated polyacrylamide beads (PB-SEA). This inhibitory activity, mediated by IC, was also observed in the proliferative response of PBMC stimulated with SEA and soluble worm antigen preparation (SWAP). Furthermore, we observed a decrease in TNF-alpha and an increase in IL-10 production by PBMC treated with IC in an in vitro granuloma reaction. This phenomenon was also seen in a cell proliferation assay when PBMC were treated with IC and stimulated with S. mansoni antigens. These results demonstrate that circulating IC may down-regulate PBMC reactivity to S. mansoni antigens by changing the cytokine pattern produced by these cells.

Granulomatous hypersensitivity to Schistosoma mansoni EGG antigens in human schistosomiasis. IV. A role for prostaglandin-induced inhibition of in vitro granuloma formation

The prostaglandins (PG) are known to regulate immune cell function(s) and participate in the progression of both acute and chronic inflammatory reactions. Using an in vitro model of Schistosoma mansoni egg-induced hypersensitivity granulomas, we have delineated the role of immune complexes (IC) in the induction and release of PG and their inhibitory effects on granuloma development. The hypersensitivity-type granuloma reaction to soluble egg antigen (SEA) was examined using a model of in vitro granuloma formation. Our results show that granuloma formation was dramatically suppressed by the addition to the granuloma cultures of IC, PGE1, PGE2, while PGF2 alpha had no significant effect. The inhibition of the PG function was achieved by the introduction of anti-PG antibodies that blocked suppression of granuloma formation. It appears in this model system that IC may inhibit the activity of granuloma formation by stimulating the monocyte-macrophage lineage to release inhibitory mediators. Our results suggest that the prostaglandins E series may be important in the generation and maintenance of suppression of the granulomatous inflammatory response to S. mansoni egg antigens.

In vitro granuloma modulation induced by immune complexes in human Schistosomiasis mansoni

Immune complexes (IC) were isolated from sera of six chronic schistosomiasis patients in order to study the regulatory mechanisms of granulomatous hypersensitivity to Schistosoma mansoni egg antigens in vitro. Purified blood mononuclear cells (PBMC) from patients (N = 14) with active schistosome infection when treated with a pool of isolated IC were able to inhibit granulomatous hypersensitivity as determined in an in vitro model of granuloma formation. The suppressive effect of IC on granuloma index varied from 33% to 73%. Analysis of the in vitro proliferation of PBMC from individuals infected with S. mansoni on blastogenesis assay (N = 7) showed that isolated IC were able to induce a suppression degree on cell proliferation from 31% to 93%. Significant inhibition of the in vitro granuloma reaction continued to be present after treatment of PBMC with supernatant from IC treated chronic patient cells. These results demonstrate that circulating IC may down-regulate granulomatous hypersensitivity to S. mansoni eggs in patients with chronic intestinal schistosomiasis.