Inhibiting the CB1 receptor in CIH-induced animal model alleviates colon injury.

Obstructive sleep apnea (OSA) can lead to intestinal injury, endotoxemia, and disturbance of intestinal flora. Additionally, as a crucial component of the endocannabinoid system, some studies have demonstrated that cannabinoid 1 (CB1) receptors are closely linked to the multiple organ dysfunction triggered by OSA. However, the role of the CB1 receptor in alleviating OSA-induced colon injury remains unclear. Here, through the construction of the OSA classic model, we found that the colon tissue of chronic intermittent hypoxia (CIH)-induced mice exhibited an overexpression of the CB1 receptor. The results of hematoxylin-eosin staining and transmission electron microscopy revealed that inhibition of the CB1 receptor could decrease the gap between the mucosa and muscularis mucosae, alleviate mitochondrial swelling, reduce microvilli shedding, and promote the recovery of tight junctions of CIH-induced mice. Furthermore, CB1 receptor inhibition reduced the levels of metabolic endotoxemia and inflammatory responses, exhibiting significant protective effects on the colon injury caused by CIH. At the molecular level, through western blotting and real-time polymerase chain reaction techniques, we found that inhibiting the CB1 receptor can significantly increase the expression of ZO-1 and Occludin proteins, which are closely related to the maintenance of intestinal mucosal barrier function. Through 16S rRNA high-throughput sequencing and short-chain fatty acid (SCFA) determination, we found that inhibition of the CB1 receptor increased the diversity of the microbial flora and controlled the makeup of intestinal flora. Moreover, butyric acid concentration and the amount of SCFA-producing bacteria, such as Ruminococcaceae and Lachnospiraceae, were both markedly elevated by CB1 receptor inhibition. The results of the spearman correlation study indicated that Lachnospiraceae showed a positive association with both ZO-1 and Occludin but was negatively correlated with the colon CB1 receptor, IL-1ß, and TNF-α. According to this study, we found that inhibiting CB1 receptor can improve CIH-induced colon injury by regulating gut microbiota, reducing mucosal damage and promoting tight junction recovery. KEY POINTS: •CIH leads to overexpression of CB1 receptor in colon tissue. •CIH causes intestinal flora disorder, intestinal mucosal damage, and disruption of tight junctions. •Inhibition of CB1 receptor can alleviate the colon injury caused by CIH through regulating the gut microbiota, reducing mucosal injury, and promoting tight junction recovery.

A systematic review of guidelines for dual antiplatelet therapy in coronary artery bypass graft.

BACKGROUND: In most situations, many patients undergoing coronary artery bypass graft (CABG) are on dual antiplatelet therapy (DAPT), which is also required after CABG. The adjustment of antiplatelet strategy remains controversial. In this study, we systematically review current guidelines, seeking consensus and controversies to facilitate clinical practice. METHODS AND RESULTS: Guidelines are searched in PubMed, Embase, ECRI Guidelines Trust and websites of guidelines organizations and professional society. Guidelines with recommendations of DAPT for patients undergo CABG are included. Two reviewers appraised guidelines with the Appraisal of Guidelines for Research and Evaluation II (AGREE II). Relevant recommendations are extracted and summarized. A total of 14 guidelines meeting inclusion criteria are selected, with average AGREE II scores from 44% to 86%. Most guidelines score high in domains other than 'applicability'. Many guidelines are not detailed enough in reporting considerations behind recommendations. Current guidelines are consistent on the management of antiplatelet strategy before elective CABG and using DAPT after surgery for preventing graft vessel occlusion. Evidence is still lacking in urgent CABG and resumption of the previous DAPT after surgery. CONCLUSIONS: Current guidelines on DAPT in CABG are generally satisfying. Suspending P2Y12 inhibitors while aspirin continued before elective CABG is recommended, as well as 12 months of DAPT following CABG. More evidence is needed to guide antiplatelet therapy in urgent CABG and to prove the benefits of resuming previous DAPT.

Optimized transformation of Streptomyces sp. ATCC 39366 producing leptomycin by electroporation.

Streptomyces sp. ATCC 39366 produces leptomycin derivatives. Leptomycin B, a potent and specific inhibitor against the export of nuclear proteins, is the main product; however, the introduction of DNA into this strain is almost impossible, which has impeded its further use. We developed a Streptomyces sp. ATCC 39366 transformation protocol to introduce foreign DNA via electroporation. Various conditions were examined, including treatments of the cell wall with weakening agents, electroporation parameters, and DNA content. We found that only plasmid DNA isolated from a dam (-) ET12567 strain resulted in successful transformation. The mycelium growing in a yeast-peptone-dextrose medium supplemented with 1% glycine at 28°C on a rotary shaker (220 rpm) was more dispersed than those without supplementation and prone to electroporation. The maximum transformation efficiency of 8×10(2) CFU/µg plasmid DNA was obtained at a field strength of 13 kV/cm with a time constant of 13 ms (25-µF capacitor; parallel resistance, 600 Ω) using 1-mm electrocuvettes. The results of the transformations of two other Streptomyces species indicated that the optimized conditions established in this study might only be applicable to Streptomyces sp. ATCC 39366. However, this is the first report of successful transformation of Streptomyces sp. ATCC 39366, and will facilitate the construction of a gene knockout mutant in Streptomyces sp. ATCC 39366 to produce series of new leptomycin derivatives.

Inactivation of recombinant human brain-type creatine kinase during denaturation by guanidine hydrochloride in a macromolecular crowding system.

In this study, we quantitatively examined the effects of the macromolecular crowding agents, polyethylene glycol 2000 (PEG 2000) and dextran 70, on guanidine hydrochloride (GdnHCl)-induced denaturation of recombinant human brain-type creatine kinase (rHBCK). Our results showed that both PEG 2000 and dextran 70 had a protective effect on the inactivation of rHBCK induced by 0.5 M GdnHCl at 25 °C. The presence of 200 g/L PEG 2000 resulted in the retention of 35.33 % of rHBCK activity after 4 h of inactivation, while no rHBCK activity was observed after denaturation in the absence of macromolecular crowding agents. The presence of PEG 2000 and dextran 70 at a concentration of 100 g/L could decelerate the k (2) value of the slow track to 21 and 33 %, respectively, in comparison to values obtained in the absence of crowding agents. Interestingly, inactivation of rHBCK in the presence of 200 g/L PEG 2000 followed first-order monophasic kinetics, with an apparent rate constant of 8 × 10(-5) s(-1). The intrinsic fluorescence results showed that PEG 2000 was better than dextran 70 at stabilizing rHBCK conformation. In addition, the results of the phase diagram indicate that more intermediates may be captured when rHBCK is denatured in a macromolecular crowding system. Mixed crowding agents did not produce better results than single crowding agents, but the protective effects of PEG 2000 on the inactivation and unfolding of rHBCK tended to increase as the ratio of PEG 2000 increased in the mixed crowding agent solution. Though it is not clear which crowding agents more accurately simulated the intracellular environment, this study could lead to a better understanding of protein unfolding in the intracellular environment.

Effects of osmolytes on human brain-type creatine kinase folding in dilute solutions and crowding systems.

The effects of osmolytes on the unfolding and refolding process of recombinant human brain-type creatine kinase (rHBCK) were comparatively, quantitatively studied in dilute solutions and macromolecular crowding systems (simulated by 100 g/L polyethylene glycol 2000), respectively. The results showed that the osmolytes, including glycerol, sucrose, dimethylsulfoxide, mannitol, inositol, and xylitol, could both protect the rHBCK from denaturation induced by 0.8 M GdnHCl and aid in the refolding of denatured-rHBCK in macromolecular crowding systems. When we examined the effects of sucrose and xylitol on the parameters of residual activity, reaction kinetics and intrinsic fluorescence of rHBCK during unfolding, it was found that the protecting effects of osmolytes in a macromolecular crowding system were more significant compared with those in a dilute solution, which resulted in more residual activities, protected the conformational changes and greatly decreased the rates of both the fast and slow tracks. Regarding the effects of glycerol, sucrose and mannitol on the denatured-rHBCK refolding parameters of refolding yield, reaction kinetics and aggregation, the results indicated that the osmolytes could alleviate the aggregation of rHBCK during refolding in both dilute solutions and macromolecular crowding systems, and the refolding yields and reaction rates under macromolecular crowding environment could be increased by the addition of osmolytes, though higher yields were obtained in the dilute solution. For further insight, osmolyte docking simulations and rHBCK denaturation were conducted successfully and confirmed our experimental results. The predictions based on the docking simulations suggested that the deactivation of guanidine may be blocked by osmolytes because they share common binding sites on rHBCK, and the higher number of interactions with rHBCK by osmolytes than guanidine may be one of the causes of rHBCK refolding. In brief, the additive effects of the exclusive volume effect from the macromolecular crowding system and the osmophobic effects from the osmolytes resulted in better performance of the osmolytes in a macromolecular crowding system, which also led to a better understanding of protein folding in the intracellular environment.

Effects of macromolecular crowding on refolding of recombinant human brain-type creatine kinase.

In this study, we quantitatively measured the effects of the macromolecular crowding agents, polyethylene glycol 2000 (PEG 2000), dextran 70, and calf thymus DNA (CT DNA), on the refolding and aggregation of recombinant human brain-type creatine kinase (rHBCK) denatured by guanidine hydrochloride (GdnHCl). The results showed that there is more aggregation in the presence of either a single crowding agent or in a mixture of crowding agents than in the absence of crowding agents, especially in the presence of a mixture containing CT DNA and PEG 2000 (or dextran 70). In the presence of high concentrations of PEG 2000 (100 g/L), dextran 70 (100 g/L), and CT DNA (15 g/L), the refolding yield remarkably decreased from 70% to 20%, 52% and 57%, respectively. A remarkable decrease in the refolding yield and rate with mixed crowding agent containing CT DNA and PEG 2000 (or dextran 70) was also observed. In comparison to refolding in the presence of 100 g/L PEG 2000, the refolding yields and rates improved in the presence of a mixture of PEG 2000 and dextran 70. We speculate that the crowding agents can favor both correct folding and misfolding/aggregation of denatured-rHBCK. Though it is not known what combination of crowding agents most accurately reflects the physiological environment within a cell, we believe our study could contribute to the understanding of protein folding and the factors that contribute to proper conformation and function in the intracellular environment.

The Effect of D-(-)-arabinose on Tyrosinase: An Integrated Study Using Computational Simulation and Inhibition Kinetics.

Tyrosinase is a ubiquitous enzyme with diverse physiologic roles related to pigment production. Tyrosinase inhibition has been well studied for cosmetic, medicinal, and agricultural purposes. We simulated the docking of tyrosinase and D-(-)-arabinose and found a binding energy of -4.5 kcal/mol for theup-formof D-(-)-arabinose and -4.4 kcal/mol for thedown-form of D-(-)-arabinose. The results of molecular dynamics simulation suggested that D-(-)-arabinose interacts mostly with HIS85, HIS259, and HIS263, which are believed to be in the active site. Our kinetic study showed that D-(-)-arabinose is a reversible, mixed-type inhibitor of tyrosinase (α-value = 6.11 ± 0.98, K(i) = 0.21 ± 0.19 M). Measurements of intrinsic fluorescence showed that D-(-)-arabinose induced obvious tertiary changes to tyrosinase (binding constant K = 1.58 ± 0.02 M(-1), binding number n = 1.49 ± 0.06). This strategy of predicting tyrosinase inhibition based on specific interactions of aldehyde and hydroxyl groups with the enzyme may prove useful for screening potential tyrosinase inhibitors.