Search for non-lactam inhibitors of mtb ß-lactamase led to its open shape in apo state: new concept for antibiotic design.

Mtb ß-lactamase (BlaC) is extremely efficient in hydrolyzing ß-lactam antibiotics which renders/leads to protection and/or resistance to this bug. There is a compelling need to develop new non-lactam inhibitors which can bind and inhibit BlaC, but cannot be hydrolyzed, thus neutralizing this survival mechanism of Mtb. Using the crystal structure of BlaC we screened 750000 purchasable compounds from ZINC Database for their theoretical affinity to the enzyme's active site. 32 of the best hits of the compounds having tetra-, tri- and thiadi-azole moiety were tested in vitro, and 4 efficiently inhibited the enzymatic activity of recombinant BlaC. Characterization of the shape of BlaC-/+ inhibitors by small angle X-ray scattering (SAXS) brought forth that BlaC adopts: (1) an open shape (radius of gyration of 2.3 nm compared to 1.9 nm of crystal structures) in solution; (2) closed shape similar to observed crystal structure(s) in presence of effective inhibitor; and (3) a closed shape which opens up when a hydrolysable inhibitor is present in solution. New BlaC inhibitors were: 1-(4-(pyridin-3-yl)-thiazol-2-ylamino)-2-(7,8,9-triaza-bicyclo[4.3.0]nona-1(6),2,4,8-tetraen-7-yl)-ethanone; 8-butyl-3-((5-(pyridin-2-yl)-4H-1,2,4-triazol-3-ylamino)-formyl)-8-aza-bicyclo[4.3.0]nona-1(6),2,4-triene-7,9-dione; 1-(3-((5-(5-bromo-thiophen-2-yl)-1,3,4-oxadiazol-2-yl)-methoxy)-phenyl)-1H-1,2,3,4-tetraazole; and 1-(2,3-dimethyl-phenylamino)-2-(2-(1-(2-methoxy-5-methyl-phenyl)-1H-1,2,3,4-tetraazol-5-ylsulfanyl)-acetylamino)-ethanone. The open-close shape of BlaC questions the physiological significance of the closed shape known for BlaC-/+ inhibitors and paves new path for structure aided design of novel inhibitors.

Caerulomycin A inhibits Th2 cell activity: a possible role in the management of asthma.

We have recently demonstrated that Caerulomycin A induces regulatory T cells differentiation by suppressing Th1 cells activity. The role of regulatory T cells is well established in suppressing the function of Th2 cells. Th2 cells are known to inflict the induction of the activation of asthma. Consequently, in the present study, we monitored the influence of Caerulomycin A in inhibiting the activity of Th2 cells and its impact in recuperating asthma symptoms. Interestingly, we observed that Caerulomycin A significantly suppressed the differentiation of Th2 cells, as evidenced by downregulation in the GATA-3 expression. Further, decline in the levels of IL-4, IL-5 and IL-13 cytokines and IgE was noted in the animals suffering from asthma. Furthermore, we noticed substantial suppression in the inflammatory response and number of eosinophils in the lungs. In essence, this study signifies an important therapeutic role of Caerulomycin A in asthma.