Baccharis dracunculifolia DC (Asteraceae) selectively modulates the effector functions of human neutrophils.

OBJECTIVES: To examine whether the hydroalcoholic extract from Baccharis dracunculifolia leaves (BdE) modulates the human neutrophil oxidative metabolism, degranulation, phagocytosis and microbial killing capacity. METHODS: In-vitro assays based on chemiluminescence, spectrophotometry, flow cytometry and polarimetry were used, as well as docking calculations. KEY FINDINGS: At concentrations that effectively suppressed the neutrophil oxidative metabolism elicited by soluble and particulate stimuli (<10 µg/ml), without clear signs of cytotoxicity, BdE (1) inhibited NADPH oxidase and myeloperoxidase activity; (2) scavenged H2 O2 and HOCl; (3) weakly inhibited phagocytosis; and (4) did not affect neutrophil degranulation and microbial killing capacity, the expression levels of TLR2, TLR4, FcγRIIa, FcγRIIIb and CR3 and the activity of elastase and lysozyme. Caffeic acid, one of the major B. dracunculifolia secondary metabolites, did not inhibit phagocytosis but interfered in the myeloperoxidase-H2 O2 -HOCl system by scavenging H2 O2 and HOCl, and interacting with the catalytic residues His-95, Arg-239 and Gln-91. CONCLUSIONS: BdE selectively modulates the effector functions of human neutrophils, inhibits the activity of key enzymes and scavenges physiological oxidant species. Caffeic acid contributes to lower the levels of oxidant species. Our findings help to unravel the mechanisms by which these natural products exert immunomodulatory action towards neutrophils.

Cross-reactivity and inhibition myotoxic effects induced by Bothrops snake venoms using specific polyclonal anti-BnSP7 antibodies.

Polyclonal antibodies raised in Balb-c mice against BnSP-7, a Lys-49 phospholipase A2, were used to measure cross reactivity against other snake venoms. Using ELISA, these antibodies were able to recognize PLA2s isoforms present in venoms of botropic snakes at 1:6400, 1:3200 and 1:100 ratios (w/w). These antibodies highly recognized proteins of low molecular weight (∼14,000) from crude snake venom Bp and Bm by Western Blotting. PLA2 these venoms, by alignment of primary structures demonstrated high identity with BnSP-7 PLA2, especially in the C-terminal region. However, the crude snake venom Bd and Bj, showed low recognition. The PLA2 activity of Bothrops pauloensis, Bothrops moojeni venoms or BpPLA2-TXI was inhibited significantly when anti-BnSP-7 antibodies were incubated at 1:10 and 1:20 ratios (venoms or toxin:anti-BnSP-7, w/w), respectively. The myotoxic effect induced by the same venoms was also reduced significantly at 1:1, 1:10 and 1:20 ratios, by decreased creatine kinase levels. The anti-PLA2 polyclonal antibodies effectively recognized PLA2s from Bothrops pauloensis and Bothrops moojeni venoms, and neutralized specific catalytic and myotoxic activity.