Discovery and characterization of novel small-molecule inhibitors targeting nicotinamide phosphoribosyltransferase.

Nicotinamide phosphoribosyltransferase (NAMPT) is a promising anticancer target. Using high throughput screening system targeting NAMPT, we obtained a potent NAMPT inhibitor MS0 (China Patent ZL201110447488.9) with excellent in vitro activity (IC50 = 9.87 ± 1.15 nM) and anti-proliferative activity against multiple human cancer cell lines including stem-like cancer cells. Structure-activity relationship studies yielded several highly effective analogues. These inhibitors specifically bound NAMPT, rather than downstream NMNAT. We provided the first chemical case using cellular thermal shift assay to explain the difference between in vitro and cellular activity; MS7 showed best in vitro activity (IC50 = 0.93 ± 0.29 nM) but worst cellular activity due to poor target engagement in living cells. Site-directed mutagenesis studies identified important residues for NAMPT catalytic activity and inhibitor binding. The present findings contribute to deep understanding the action mode of NAMPT inhibitors and future development of NAMPT inhibitors as anticancer agents.

Chronic nicotine treatment enhances vascular smooth muscle relaxation in rats.

AIM: To investigate the effect of chronic nicotine treatment on vascular function and to identify the underlying mechanisms. METHODS: Adult rats were treated with nicotine (3 mg·kg(-1)·d(-1), sc) for 6 weeks. After the rats were sacrificed, aortic rings were prepared for detecting vascular reactivity, and thoracic aorta and periaortic fat samples were collected for histological and molecular biology studies. RESULTS: Chronic nicotine treatment significantly reduced periaortic fat, and specifically enhanced smooth muscle relaxation without altering the aortic adventitial fat and endothelium function. Pretreatment with the soluble guanylyl cyclase inhibitor ODQ (3 µmol/L) or PKG inhibitor Rp-8-Br-PET-cGMP (30 µmol/L) abolished the nicotine-induced enhancement of smooth muscle relaxation, whereas the cGMP analogue 8-Br-cGMP could mimic the nicotine-induced enhancement of smooth muscle relaxation. However, the chronic nicotine treatment did not alter PKG protein expression and activity in aortic media. CONCLUSION: Chronic nicotine treatment enhances vascular smooth muscle relaxation of rats via activation of PKG pathway.

Rapid inhibitory effect of glucocorticoids on airway smooth muscle contractions in guinea pigs.

The common disease asthma is characterized by the obstruction, inflammation and increased sensitivity of the airways. Glucocorticoids (GCs) are one of the most potent anti-inflammatory agents available for treating allergic disease. In this study, we report that the GC budesonide (BUD) can rapidly inhibit the histamine-induced contractions of airway smooth muscle in a process mediated by non-genomic mechanisms. The tracheas of albino Hartley guinea pigs were used. We measured the effects of BUD on the increased isometric tension of trachea segment rings and the shrinking of single airway smooth muscle cells (ASMCs) induced by histamine. With the application of each reagent, the changes in the isometric tension of the segment rings upon maximum contraction and at four time points were recorded. We found that BUD significantly suppressed the increase in isometric tension induced by histamine in guinea pigs within 15 min. We also observed that BUD can reduce the histamine-induced shrinking of single ASMCs in an even shorter time. Mifepristone (RU486) and actidione did not depress the inhibitory effect of BUD. The results preclude action via genomic-mediated responses that usually take several hours to occur. We conclude therefore that GCs have a rapid non-genomic inhibitory effect on guinea pig airway smooth muscle contractions, and provide a new way to investigate this non-genomic mechanism. Further study can provide theoretical evidence for the clinical application of GCs in asthma and other allergic diseases.

Two useful methods for evaluating antihypertensive drugs in conscious freely moving rats.

AIM: Computerized analysis of blood pressure in conscious freely moving rats is a sound technique for physiological and pharmacological studies. The present work, based on this technique, was designed to introduce two useful methods for the evaluation of antihypertensive drugs in conscious spontaneously hypertensive rat (SHR). They were the directly intragastric administration of drugs and modified probability sum test for evaluating the synergism of the combination of two drugs. METHODS AND RESULTS: (1) Directly intragastric administration was used in conscious rats. A catheter was inserted into stomach immediately after arterial catheter insertion. Three days after operation, blood pressure was recorded and drug might be given intragastrically via the gastric catheter. (2) Modified probability sum test was used to evaluate the synergism of two drugs. The formula was: q=P(A+B)/(PA+PB-PAxB). With this method, it was obtained: q=1.32 for the effects of the combination of atenolol and nitrendipine (20 mg/kg+10 mg/kg) on systolic blood pressure; q=1.41 for the effects of the combination of atenolol and amlodipine (10 mg/kg+1 mg/kg) on systolic blood pressure. CONCLUSION: The two methods introduced by the present work will be important and useful for antihypertensive drug evaluation in conscious freely moving rats.