Papaverine Prevents Vasospasm by Regulation of Myosin Light Chain Phosphorylation and Actin Polymerization in Human Saphenous Vein

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

Is Prolonged Use of Antibiotic Prophylaxis and Postoperative Antithrombotic and Antispasmodic Treatments Necessary After Digit Replantation or Revascularization?

BACKGROUND

Ensuring the patency of repaired vessels is pivotal in improving the success rate of digit replantation. There is no consensus on how to best approach postoperative treatment for digit replantation. The influence of postoperative treatment on the risk of failure of revascularization or replantation remains unclear.

QUESTIONS/PURPOSES

(1) Is there an increased risk of postoperative infection with early discontinuation of antibiotic prophylaxis? (2) How are anxiety and depression affected by a treatment protocol consisting of prolonged antibiotic prophylaxis and administration of antithrombotic and antispasmodic drugs and by the failure of a revascularization or replantation procedure? (3) Are there differences in the risk of revascularization or replantation failure based on the number of anastomosed arteries and veins? (4) What factors are associated with failure of revascularization or replantation?

METHODS

This retrospective study was conducted between July 1, 2018, and March 31, 2022. Initially, 1045 patients were identified. One hundred two patients chose revision of amputation. In all, 556 were excluded because of contraindications. We included all patients in whom the anatomic structures of the amputated part of the digit were well preserved, and those with an ischemia time for the amputated part that did not exceed 6 hours. Patients in good health without any other serious associated injuries or systemic diseases and those without a history of smoking were eligible for inclusion. The patients underwent procedures that were performed or supervised by one of four study surgeons. Patients were treated with antibiotic prophylaxis (1 week); patients treated with antithrombotic and antispasmodic drugs were categorized into the prolonged antibiotic prophylaxis group. The remaining patients treated with antibiotic prophylaxis for less than 48 hours and no antithrombotic and no antispasmodic drugs were categorized into the nonprolonged antibiotic prophylaxis group. Postoperative follow-up was for a minimum of 1 month. Based on the inclusion criteria, 387 participants with 465 digits were selected for an analysis of postoperative infection. Twenty-five participants with a postoperative infection (six digits) and other complications (19 digits) were excluded from the next stage of the study, in which we assessed factors associated with the risk of failure of revascularization or replantation. A total of 362 participants with 440 digits were examined, including the postoperative survival rate, variation in Hospital Anxiety and Depression Scale scores, the association between the survival rate and Hospital Anxiety and Depression Scale scores, and the survival rate based on the number of anastomosed vessels. Postoperative infection was defined as swelling, erythema, pain, purulent discharge, or a positive bacterial culture result. Patients were followed for 1 month. The differences in anxiety and depression scores between the two treatment groups and the differences in anxiety and depression scores based on failure of revascularization or replantation were determined. The difference in the risk of revascularization or replantation failure based on the number of anastomosed arteries and veins was assessed. Except for statistically significant variables (injury type and procedure), we thought that the number of arteries, number of veins, Tamai level, treatment protocol, and surgeons would be important. A multivariable logistic regression analysis was used to perform an adjusted analysis of risk factors such as postoperative protocol, injury type, procedure, number of arteries, number of veins, Tamai level, and surgeon.

RESULTS

Postoperative infection did not appear to increase without prolonged use of antibiotic prophylaxis beyond 48 hours (1% [3 of 327] versus 2% [3 of 138]; OR 2.4 [95% confidence interval (CI) 0.5 to 12.0]; p = 0.37). Intervention with antithrombotic and antispasmodic therapy increased the Hospital Anxiety and Depression Scale scores for anxiety (11.2 ± 3.0 versus 6.7 ± 2.9, mean difference 4.5 [95% CI 4.0 to 5.2]; p < 0.01) and depression (7.9 ± 3.2 versus 5.2 ± 2.7, mean difference 2.7 [95% CI 2.1 to 3.4]; p < 0.01). In the analysis based on the failure of revascularization or replantation, the Hospital Anxiety and Depression Scale scores for anxiety (11.4 ± 4.4 versus 9.7 ± 3.5, mean difference 1.7 [95% CI 0.6 to 2.8]; p < 0.01) and depression (8.5 ± 4.6 versus 7.0 ± 3.1, mean difference 1.5 [95% CI 0.5 to 2.5]; p < 0.01) were higher in the failed revascularization or replantation group than in the successful revascularization or replantation group. There was no increase in the artery-related risk of failure (one versus two anastomosed arteries: 91% versus 89%, OR 1.3 [95% CI 0.6 to 2.6]; p = 0.53). For patients with anastomosed veins, a similar outcome was observed for the two vein-related risk of failure (two versus one anastomosed vein: 90% versus 89%, OR 1.0 [95% CI 0.2 to 3.8]; p = 0.95) and three vein-related risk of failure (three versus one vein anastomosed: 96% versus 89%, OR 0.4 [95% CI 0.1 to 2.4]; p = 0.29). Factors associated with failure of revascularization or replantation included the mechanism of injury (crush: OR 4.2 [95% CI 1.6 to 11.2]; p < 0.01, avulsion: OR 10.2 [95% CI 3.4 to 30.7]; p < 0.01). Revascularization had a lower risk of failure than replantation (OR 0.4 [95% CI 0.2 to 1.0]; p = 0.04). Treatment with a protocol of prolonged antibiotics, antithrombotics, and antispasmodics was not associated with a lower risk of failure (OR 1.2 [95% CI 0.6 to 2.3]; p = 0.63).

CONCLUSION

With proper wound debridement and patency of repaired vessels, prolonged use of antibiotic prophylaxis and regular antithrombotic and antispasmodic treatment may not be necessary for successful digit replantation. However, it may be associated with higher Hospital Anxiety and Depression Scale scores. Postoperative mental status is associated with digit survival. Well-repaired vessels, instead of the number of anastomosed vessels, could be critical to survival and decrease the influence of risk factors. Further research on consensus guidelines that compare postoperative treatment and the surgeon's level of expertise after digit replantation should be conducted at multiple institutions.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Phosphodiesterase type 10A inhibitor attenuates lung fibrosis by targeting myofibroblast activation

Pulmonary fibrosis (PF) is a fatal and irreversible respiratory disease accompanied by excessive fibroblast activation. Previous studies have suggested that cAMP signaling pathway and cGMP-PKG signaling pathway are continuously down-regulated in lung fibrosis, whereas PDE10A has a specifically expression in fibroblasts/myofibroblasts in lung fibrosis. In this study, we demonstrated that overexpression of PDE10A induces myofibroblast differentiation, and papaverine, as a PDE10A inhibitor used for vasodilation, inhibits myofibroblast differentiation in human fibroblasts, Meanwhile, papaverine alleviated bleomycin-induced pulmonary fibrosis and amiodarone-induced oxidative stress, papaverine downregulated VASP/β-catenin pathway to reduce the myofibroblast differentiation. Our results first demonstrated that papaverine inhibits TGFβ1-induced myofibroblast differentiation and lung fibrosis by VASP/β-catenin pathway.

The effects of botulinum toxin A and papaverine on human saphenous vein and internal mammary artery grafts: an in vitro study

INTRODUCTION

Autologous saphenous vein (SV) and internal mammary artery (IMA) are used as bypass conduits during coronary artery bypass graft surgery. Vasospasm of the arterial and venous grafts may constitute a significant clinical problem. Pretreatment with a vasodilator drug of the graft ex vivo or intraluminal injection before implantation may be used for spasm prophylaxis. This in vitro study was designed to assess the vasoactive effects and time-dependent changes of botulinum toxin A (BTX-A) and papaverine pretreatment on vasospasm of human SV and IMA grafts. Also, histomorphology of the vessels was assessed.

MATERIAL AND METHODS

SV and IMA segments were suspended in organ baths, and isometric contraction responses to 2 different concentrations of 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1) were recorded after incubation with 2 different concentrations of BTX-A and papaverine at 2 time points (0 h and 2 h).

RESULTS

The results revealed the following: 1) incubation with BTX-A and papaverine relaxes both SV and IMA rings contracted with 5-HT and ET-1; 2) the duration of the relaxant effect of BTX-A lasts longer than papaverine; and 3) no apparent histomorphological changes were observed in the grafts under light microscopy.

CONCLUSIONS

This study demonstrates that in human SV and IMA grafts, pretreatment with both BTX-A and papaverine are safe and have a potent inhibitory effect depending on the vessel and vasoconstrictor agent. The long-lasting vasodilatory effect of BTX-A on vascular smooth muscle may provide promising results in the prevention of venous and arterial graft spasm.

Extravasation of Concentrated Potassium Chloride: A Case Report

Background

The extravasation of potassium chloride will cause serious harm, especially if it is not diagnosed or treated promptly. Objective:to report the clinical course of a patient who was suffering a potassium extravasation and to discuss steps that can be done to decrease the chances of this event from occurring in other patients.

Methods

After discontinuation of infusion device and withdrawal of intravenous catheter, wet packing with magnesium sulfate and local injection of papaverine and lidocaine were applied.

Results

After 11 days, the extravasation injury had recovered.

Conclusions

To avoid a repeat of such an adverse event, proper sites for administering, accurate dilution of potassium chloride solutions, close observation, and increased awareness of trained personnel of extravasation dangers are vital. Once extravasation occurs, timely wet application with magnesium sulfate and local injection of papaverine and lidocaine may have been useful in producing a favorable recovery.

Articular Chondrocyte Phenotype Regulation through the Cytoskeleton and the Signaling Processes That Originate from or Converge on the Cytoskeleton: Towards a Novel Understanding of the Intersection between Actin Dynamics and Chondrogenic Function

Numerous studies have assembled a complex picture, in which extracellular stimuli and intracellular signaling pathways modulate the chondrocyte phenotype. Because many diseases are mechanobiology-related, this review asked to what extent phenotype regulators control chondrocyte function through the cytoskeleton and cytoskeleton-regulating signaling processes. Such information would generate leverage for advanced articular cartilage repair. Serial passaging, pro-inflammatory cytokine signaling (TNF-α, IL-1α, IL-1β, IL-6, and IL-8), growth factors (TGF-α), and osteoarthritis not only induce dedifferentiation but also converge on RhoA/ROCK/Rac1/mDia1/mDia2/Cdc42 to promote actin polymerization/crosslinking for stress fiber (SF) formation. SF formation takes center stage in phenotype control, as both SF formation and SOX9 phosphorylation for COL2 expression are ROCK activity-dependent. Explaining how it is molecularly possible that dedifferentiation induces low COL2 expression but high SF formation, this review theorized that, in chondrocyte SOX9, phosphorylation by ROCK might effectively be sidelined in favor of other SF-promoting ROCK substrates, based on a differential ROCK affinity. In turn, actin depolymerization for redifferentiation would “free-up” ROCK to increase COL2 expression. Moreover, the actin cytoskeleton regulates COL1 expression, modulates COL2/aggrecan fragment generation, and mediates a fibrogenic/catabolic expression profile, highlighting that actin dynamics-regulating processes decisively control the chondrocyte phenotype. This suggests modulating the balance between actin polymerization/depolymerization for therapeutically controlling the chondrocyte phenotype.

Arterial Network Geometric Characteristics and Regulation of Capillary Blood Flow in Hamster Skeletal Muscle Microcirculation

This study was aimed to characterize the geometric arrangement of hamster skeletal muscle arteriolar networks and to assess the in vivo rhythmic diameter changes of arterioles to clarify regulatory mechanisms of the capillary perfusion. The experimental study was carried out in male Syrian hamsters implanted with a plastic chamber in the dorsum skin under pentobarbital anesthesia. The skeletal muscle microvessels were visualized by fluorescence microscopy. The vessel diameters, lengths and the rhythmic diameter changes of arterioles were analyzed with computer-assisted techniques. The arterioles were classified according to a centripetal ordering scheme. In hamster skeletal muscle microvasculature the terminal branchings, differentiated in long and short terminal arteriolar trees (TATs), originated from anastomotic vessels, defined "arcading" arterioles. The long TATs presented different frequencies along the branching vessels; order 4 arterioles had frequencies lower than those observed in the order 3, 2, and 1 vessels. The short TAT order 3 arterioles, directly originating from "arcading" parent vessels, showed a frequency dominating all daughter arterioles. The amplitude of diameter variations in larger vessels was in the range 30-40% of mean diameter, while it was 80-100% in order 3, 2, and 1 vessels. Therefore, the complete constriction of arterioles, caused an intermittent capillary blood perfusion. L-arginine or papaverine infusion caused dilation of arterioles and transient disappearing of vasomotion waves and induced perfusion of all capillaries spreading from short and long TAT arrangements. Therefore, the capillary blood flow was modulated by changes in diameter of terminal arterioles penetrating within the skeletal muscle fibers, facilitating redistribution of blood flow according to the metabolic demands of tissues.

Relaxation matters: comparison of in-vitro vasodilatory role of botulinum toxin-A and papaverine in human radial artery grafts

Background

Radial artery (RA) is widely used in coronary artery bypass (CABG) surgery and the prevention of spasm is crucial for graft patency. Botulinum toxin A (BTX-A) and B are commonly used for aesthetic reasons and neuromuscular disorders. They are proven to raise blood flow and increase survival of ischemic skin flaps. In this study we evaluated and compared the vasodilator effects of BTX-A and papaverine on human RA grafts.

Methods

After resting 60 min in isolated organ baths, human RA grafts were examined. Contraction responses for different doses of serotonin (5-HT) and endothelin-1 (ET-1) were evaluated as a percent of maximum contraction response elicited by 80 mM potassium chloride (KCl). The inhibitory effects of BTX-A and papaverine on contraction responses taken at the 0th hour were compared with the 1st and 2nd hour responses. Inhibitory effects of BTX-A and papaverine against the contractile agent were evaluated by comparing the results of the first and last (0th and 2nd hour) application.

Results

In low concentrations, when we compared the effects of BTX-A (10^− 8 M) and papaverine (10^− 6 M) on 5-HT, papaverine was found to be more effective at both the 0th and 2nd hour (p < 0.05). Both BTX-A and papaverine inhibited the maximum contractile effect of ET-1 to the same extent at the 0th hour; but, the inhibitory effect of BTX-A was significantly stronger at the 2nd hour (p < 0.05).

In high concentrations, when we compared the effects of BTX-A (10^− 6 M) and papaverine (10^− 4 M) on 5-HT, papaverine showed stronger inhibition (p < 0.05), whereas both agents had similar action of inhibition on ET-1 mediated maximum contraction responses.

Conclusion

BTX-A inhibits both ET-1 and 5-HT induced contractions and its effectiveness does not decrease over time as observed with papaverine. This study is the first in the literature using human RA for prevention of vasospasm by BTX-A.

Implications for understanding ischemic stroke as a sexually dimorphic disease: the role of pial collateral circulations

We investigated structural and functional differences in primary and pial collateral circulations in adult normotensive male and female Wistar rats. Male ( n = 10) and female ( n = 7) rats were subjected to middle cerebral artery (MCA) occlusion and changes in relative cerebral blood flow in MCA and pial collateral territories were measured by multisite laser-Doppler flowmetry. Rats were then transcardially perfused with a mixture of carbon black and latex, perfusion fixed, and imaged to compare primary and pial collateral structure between male ( n = 4) and female ( n = 3) rats, including lumen diameters and number. To study pial collateral function, leptomeningeal anastomoses (LMAs) were isolated and pressurized from male ( n = 7) and female ( n = 6) rats. Myogenic tone and reactivity to pressure, vascular function to pharmacological activator, or inhibitor of ion channels was measured and compared. There was no difference between relative cerebral blood flow in both MCA and pial collateral territories during occlusion and reperfusion between groups. Compared with male LMAs, female LMAs had similar myogenic tone (24.0 ± 7.3% vs. 16.0 ± 3.7%, P > 0.05) and reactivity to increased pressure and similar vascular responses to vasoconstrictive and vasodilatory stimuli. Additionally, compared with female LMAs, male LMAs had similar numbers (21 ± 1 vs. 20 ± 2, P > 0.05) and diameters (30.5 ± 2.0 vs. 26.2 ± 0.6 μm, P > 0.05), and no sex difference was detected in the diameter of arterial segments of circle of Willis. Together, our data establish no sex difference of cerebral collateral structure or function, suggesting that the reduced severity of stroke outcome in female rats is not likely due to differences in the cerebral collateral circulation. NEW & NOTEWORTHY Our work compared the function of leptomeningeal anastomoses between male and female adult normotensive rats with no sex difference found. We also confirmed no sex difference in primary and pial collateral structure in Wistar rats. Our findings suggest that the reduced severity of stroke in premenopausal women and reproductively intact female rodents is not likely due to improved primary and pial collateral circulations.

Arteriolar vasodilation involves actin depolymerization

It is generally assumed that relaxation of arteriolar vascular smooth muscle occurs through hyperpolarization of the cell membrane, reduction in intracellular Ca²⁺ concentration, and activation of myosin light chain phosphatase/inactivation of myosin light chain kinase. We hypothesized that vasodilation is related to depolymerization of F-actin. Cremaster muscles were dissected in rats under pentobarbital sodium anesthesia (50 mg/kg). First-order arterioles were dissected, cannulated on glass micropipettes, pressurized, and warmed to 34°C. Internal diameter was monitored with an electronic video caliper. The concentration of G-actin was determined in flash-frozen intact segments of arterioles by ultracentrifugation and Western blot analyses. Arterioles dilated by ~40% of initial diameter in response to pinacidil (1 × 10^-6 mM) and sodium nitroprusside (5 × 10^-5 mM). The G-actin-to-smooth muscle 22α ratio was 0.67 ± 0.09 in arterioles with myogenic tone and increased significantly to 1.32 ± 0.34 ( P < 0.01) when arterioles were dilated with pinacidil and 1.14 ± 0.18 ( P < 0.01) with sodium nitroprusside, indicating actin depolymerization. Compared with control vessels (49 ± 5%), the percentage of phosphorylated myosin light chain was significantly reduced by pinacidil (24 ± 2%, P < 0.01) but not sodium nitroprusside (42 ± 4%). These findings suggest that actin depolymerization is an important mechanism for vasodilation of resistance arterioles to external agonists. Furthermore, pinacidil produces smooth muscle relaxation via both decreases in myosin light chain phosphorylation and actin depolymerization, whereas sodium nitroprusside produces smooth muscle relaxation primarily via actin depolymerization. NEW & NOTEWORTHY This article adds to the accumulating evidence on the contribution of the actin cytoskeleton to the regulation of vascular smooth muscle tone in resistance arterioles. Actin depolymerization appears to be an important mechanism for vasodilation of resistance arterioles to pharmacological agonists. Dilation to the K⁺ channel opener pinacidil is produced by decreases in myosin light chain phosphorylation and actin depolymerization, whereas dilation to the nitric oxide donor sodium nitroprusside occurs primarily via actin depolymerization.