Norman P. Jensen

Novel Saccharomyces cerevisiae Screen Identifies WR99210 Analogues That Inhibit Mycobacterium tuberculosis Dihydrofolate Reductase

ABSTRACT The ongoing selection of multidrug-resistant strains of Mycobacterium tuberculosis has markedly reduced the effectiveness of the standard treatment regimens. Thus, there is an urgent need for new drugs that are potent inhibitors of M. tuberculosis, that exhibit favorable resistance profiles, and that are well tolerated by patients. One promising drug target for treatment of mycobacterial infections is dihydrofolate reductase (DHFR; EC 1.5.1.3), a key enzyme in folate utilization. DHFR is an important drug target in many pathogens, but it has not been exploited in the search for drugs effective against M. tuberculosis. The triazine DHFR inhibitor WR99210 has been shown to be effective against other mycobacteria. We show here that WR99210 is also a potent inhibitor of M. tuberculosis and Mycobacterium bovis BCG growth in vitro and that resistance to WR99210 occurred less frequently than resistance to either rifampin or isoniazid. Screening of drugs with M. tuberculosis cultures is slow and requires biosafety level 3 facilities and procedures. We have developed an alternative strategy: initial screening in an engineered strain of the budding yeast Saccharomyces cerevisiae that is dependent on the M. tuberculosis DHFR for its growth. Using this system, we have screened 19 compounds related to WR99210 and found that 7 of these related compounds are also potent inhibitors of the M. tuberculosis DHFR. These studies suggest that compounds of this class are excellent potential leads for further development of drugs effective against M. tuberculosis.

Inhibition of the release of prostaglandins, leukotrienes and lysosomal acid hydrolases from macrophages by selective inhibitors of lecithin biosynthesis

The release of the inflammatory mediators, prostaglandins (PGs), leukotrienes (LT) and lysosomal acid hydrolases (LAH), by macrophages is stimulated by endocytic stimuli such as zymosan. This process can be interfered with by specific inhibitors of phosphatidylcholine (PC) biosynthesis. The diphenylsulfone dapsone and three analogs selectively inhibited [14C]choline incorporation into PC but had varied effects on inhibition of mediator release by macrophages. Dapsone inhibited the release of PGs, LT and LAH, whereas the three closely related structural analogs inhibited LAH release only, with little or no effect on PG production.

Biochemical and biological activities of 2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol (L-651,896), a novel topical anti-inflammatory agent

The biochemical and biological profile of a topical anti-inflammatory agent, 2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol (L-651,896 inhibited the 5-lipoxygenase of rat basophilic leukemia cells with an IC50 of 0.1 microM and leukotriene synthesis by human PMN and mouse macrophages with IC50 values of 0.4 and 0.1 microM respectively. L-651,896 also inhibited prostaglandin E2 synthesis by mouse peritoneal macrophages (IC50 = 1.1 microM). This compound inhibited ram seminal vesicle cyclooxygenase activity at considerably higher concentrations, and this effect was directly related to substrate concentration. When applied topically to the mouse ear, L-651,896 lowered elevated levels of leukotrienes associated with arachidonic acid-induced skin inflammation and delayed hypersensitivity induced by oxazolone. However, while L-651,896 inhibited the increased vascular permeability induced by arachidonic acid, it had no effect on the edema associated with the immune-based response to oxazolone in the same tissue. Thus, it is possible that leukotrienes may play a role in some but not all inflammatory responses.