Concanamycin F

The investigation of V-ATPases as potential therapeutic drug targets and hence of their specific inhibitors is a promising approach in osteoporosis and cancer treatment because the occurrence of these diseases is interrelated to the function of the V-ATPase. Apicularen belongs to the novel inhibitor family of the benzolactone enamides, which are highly potent but feature the unique characteristic of not inhibiting V-ATPases from fungal sources. In this study we specify, for the first time, the binding site of apicularen within the membrane spanning V(O) complex. By photoaffinity labeling using derivatives of apicularen and of the plecomacrolides bafilomycin and concanamycin, each coupled to (14)C-labeled 4-(3-trifluoromethyldiazirin-3-yl)benzoic acid, we verified that apicularen binds at the interface of the V(O) subunits a and c. The binding site is in the vicinity to those of the plecomacrolides and of the archazolids, a third family of V-ATPase inhibitors. Expression of subunit c homologues from Homo sapiens and Manduca sexta, both species sensitive to benzolactone enamides, in a Saccharomyces cerevisiae strain lacking the corresponding intrinsic gene did not transfer this sensitivity to yeast. Therefore, the binding site of benzolactone enamides cannot be formed exclusively by subunit c. Apparently, subunit a substantially contributes to the binding of the benzolactone enamides.

Pterostilbene (PTE) is broadly found in berries and has antioxidant and anti-inflammatory properties. To examine the effect of PTE on acute liver injury, mice were administrated PTE prior to concanavalin A (ConA). The mice were divided into the following groups: (i) vehicle control, (ii) ConA alone, (iii) ConA with PTE at 10 mg kg-1 (PTE low dose, PTL), and (iv) ConA with PTE at 40 mg kg-1 (PTE high dose, PTH). After the ConA challenge, the mice showed prompt induction of intrahepatic IFN-γ and TNF-α, followed by tissue factor (TF), which aggravated the fibrin deposition and massive liver necrosis. However, these effects were significantly counteracted by the PTE pretreatment. Furthermore, PTE reversed the phosphorylation of ConA-induced intrahepatic inflammatory kinases including JNK, ERK1/2, p38 and p65. Interestingly, PTE did not directly act on the hepatocytes, but inhibited intrahepatic macrophage accumulation and TF generation by inhibiting the activation of inflammatory p38 MAPK. These results suggest a promising avenue for the exploration of pterostilbene in improving acute liver injury.

Multinucleated giant cells (MGC) are characteristic cells in granulomatous disorders such as paracoccidioidomycosis (PCM) and also are formed in vitro from peripheral blood mononuclear cells by several stimuli. In this study, the authors investigated in vitro formation of MGC derived from monocytes of healthy individuals, stimulated with Paracoccidioides brasiliensis antigen (PbAg), compared with other stimuli such as IFN-gamma and supernatant of Con-A-stimulated peripheral blood mononuclear cells (CM-ConA). Besides, the fungicidal activity of monocytes and monocyte-derived MGC challenged with P. brasiliensis were compared, at a ratio of one fungus per 50 monocytes. Results demonstrated that PbAg, IFN-gamma, and CM-ConA stimuli were able to induce MGC generation, with fusion indices significantly higher than control cultures. Striking results were observed when MGC induced by PbAg and IFN-gamma presented higher fungicidal activity than monocytes, submitted to the same stimuli, showing a better capacity of these cells to kill P. brasiliensis. In summary, the results suggest that PbAg is able to induce MGC generation, and these cells presented higher fungicidal activity against P. brasiliensis than monocytes.