Protein Kinase C Isoforms Distinctly Regulate Propofol-induced Endothelium-dependent and Endothelium-independent Vasodilation:

Altered levels of phospholipases C, diacylglycerols, endocannabinoids, and N-acylethanolamines in patients with hereditary angioedema due to FXII mutation

BACKGROUND

Hereditary angioedema (HAE) is a rare genetic disorder characterized by local, self-limiting edema due to temporary increase in vascular permeability. HAE with normal C1 esterase inhibitor (C1INH) activity includes the form with mutations in the F12 gene encoding for coagulation factor XII (FXII-HAE) causing an overproduction of bradykinin (BK) leading to angioedema attack. BK binding to B2 receptors (BK2R) leads to an activation of phospholipase C (PLC) and subsequent generation of second messengers: diacylglycerols (DAGs) and possibly the endocannabinoids (eCBs), 2-arachidonoylglycerol (2-AG) and anandamide (AEA), and eCB-related N-acylethanolamines [palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)]. To date, there are no data on the role of these lipid mediators in FXII-HAE.

METHODS

Here, we analyzed plasma levels of PLC, DAGs, and eCBs in 40 patients with FXII-HAE and 40 sex- and age-matched healthy individuals.

RESULTS

Plasma PLC activity was increased in FXII-HAE patients compared to controls. Concentrations of DAG 18:1-20:4, a lipid second messenger produced by PLC, were higher in FXII-HAE compared to controls, and positively correlated with PLC activity and cleaved high molecular kininogen (cHK). Also the concentrations of the DAG metabolite, 2-AG were altered in FXII-HAE. AEA and OEA were decreased in FXII-HAE patients compared to controls; by contrast, PEA, was increased. The levels of all tested mediators did not differ between symptomatic and asymptomatic patients. Moreover, C1INH-HAE patients had elevated plasma levels of PLC, which correlated with cHK, but the levels of DAGs and eCBs were the same as controls.

CONCLUSIONS

BK overproduction and BKR2 activation are linked to alteration of PLCs and their metabolites in patients with FXII-HAE. Our results may pave way to investigations on the functions of these mediators in the pathophysiology of FXII-HAE, and provide new potential biomarkers and therapeutic targets.

C2CD4B Evokes Oxidative Stress and Vascular Dysfunction via a PI3K/Akt/PKCα-Signaling Pathway

High glucose-induced endothelial dysfunction is an important pathological feature of diabetic vasculopathy. While genome-wide studies have identified an association between type 2 diabetes mellitus (T2DM) and increased expression of a C2 calcium-dependent domain containing 4B (C2CD4B), no study has yet explored the possible direct effect of C2CD4B on vascular function. Vascular reactivity studies were conducted using a pressure myograph, and nitric oxide and oxidative stress were assessed through difluorofluorescein diacetate and dihydroethidium, respectively. We demonstrate that high glucose upregulated both mRNA and protein expression of C2CD4B in mice mesenteric arteries in a time-dependent manner. Notably, the inhibition of C2CD4B expression by genetic knockdown efficiently prevented hyperglycemia-induced oxidative stress, endothelial dysfunction, and loss of nitric oxide (NO) bioavailability. Recombinant C2CD4B evoked endothelial dysfunction of mice mesenteric arteries, an effect associated with increased reactive oxygen species (ROS) and decreased NO production. In isolated human umbilical vein endothelial cells (HUVECs), C2CD4B increased phosphorylation of endothelial nitric oxide synthase (eNOS) at the inhibitory site Thr495 and reduced eNOS dimerization. Pharmacological inhibitors of phosphoinositide 3-kinase (PI3K), Akt, and PKCα effectively attenuated oxidative stress, NO reduction, impairment of endothelial function, and eNOS uncoupling induced by C2CD4B. These data demonstrate, for the first time, that C2CD4B exerts a direct effect on vascular endothelium via a phosphoinositide 3-kinase (PI3K)/Akt/PKCα-signaling pathway, providing a new perspective on C2CD4B as a promising therapeutic target for the prevention of oxidative stress in diabetes-induced endothelial dysfunction.

General anaesthesia-related complications of gut motility with a focus on cholinergic mechanisms, TRP channels and visceral pain

General anesthesia produces multiple side effects. Notably, it temporarily impairs gastrointestinal motility following surgery and causes the so-called postoperative ileus (POI), a multifactorial and complex condition that develops secondary to neuromuscular failure and mainly affects the small intestine. There are currently limited medication options for POI, reflecting a lack of comprehensive understanding of the mechanisms involved in this complex condition. Notably, although acetylcholine is one of the major neurotransmitters initiating excitation-contraction coupling in the gut, cholinergic stimulation by prokinetic drugs is not very efficient in case of POI. Acetylcholine when released from excitatory motoneurones of the enteric nervous system binds to and activates M2 and M3 types of muscarinic receptors in smooth muscle myocytes. Downstream of these G protein-coupled receptors, muscarinic cation TRPC4 channels act as the major focal point of receptor-mediated signal integration, causing membrane depolarisation accompanied by action potential discharge and calcium influx via L-type Ca²⁺ channels for myocyte contraction. We have recently found that both inhalation (isoflurane) and intravenous (ketamine) anesthetics significantly inhibit this muscarinic cation current (termed mI _CAT) in ileal myocytes, even when G proteins are activated directly by intracellular GTPγS, i.e., bypassing muscarinic receptors. Here we aim to summarize Transient Receptor Potential channels and calcium signalling-related aspects of the cholinergic mechanisms in the gut and visceral pain, discuss exactly how these may be negatively impacted by general anaesthetics, while proposing the receptor-operated TRPC4 channel as a novel molecular target for the treatment of POI.

A phase I trial of LXS196, a protein kinase C (PKC) inhibitor, for metastatic uveal melanoma

BACKGROUND

Up to 50% of patients with uveal melanoma develop metastases (MUM) with a poor prognosis and median overall survival of approximately 1 year.

METHODS

This phase I study evaluated the safety, tolerability, pharmacokinetics, pharmacodynamics and efficacy of the oral protein kinase C inhibitor LXS196 in 68 patients with MUM (NCT02601378). Patients received LXS196 doses ranging from 100-1000 mg once daily (QD; n = 38) and 200-400 mg twice daily (BID; n = 30).

RESULTS

First cycle dose-limiting toxicities (DLTs) were observed in 7/38 (18.4%) QD and 2/17 (11.8%) BID patients. Hypotension was the most common DLT, occurring at doses ≥500 mg/day, and manageable with LXS196 interruption and dose reduction. Median duration of exposure to LXS196 was 3.71 months (range: 1.81-15.28) for QD and 4.6 months (range: 0.33-58.32) for BID dosing. Clinical activity was observed in 6/66 (9.1%) evaluable patients achieving response (CR/PR), with a median duration of response of 10.15 months (range: 2.99-41.95); 45/66 had stable disease (SD) per RECIST v1.1. At 300 mg BID, the recommended dose for expansion, 2/18 (11.1%) evaluable patients achieved PR and 12/18 (66.7%) had SD.

CONCLUSION

These results suggest manageable toxicity and encouraging clinical activity of single-agent LXS196 in patients with MUM.

TRPA1 Polymorphisms Modify the Hypotensive Responses to Propofol with No Change in Nitrite or Nitrate Levels

Anesthesia with propofol is frequently associated with hypotension. The TRPA1 gene contributes to the vasodilator effect of propofol. Hypotension is crucial for anesthesiologists because it is deleterious in the perioperative period. We tested whether the TRPA1 gene polymorphisms or haplotypes interfere with the hypotensive responses to propofol. PCR-determined genotypes and haplotype frequencies were estimated. Nitrite, nitrates, and NOx levels were measured. Propofol induced a more expressive lowering of the blood pressure (BP) without changing nitrite or nitrate levels in patients carrying CG+GG genotypes for the rs16937976 TRPA1 polymorphism and AG+AA genotypes for the rs13218757 TRPA1 polymorphism. The CGA haplotype presented the most remarkable drop in BP. Heart rate values were not impacted. The present exploratory analysis suggests that TRPA1 genotypes and haplotypes influence the hypotensive responses to propofol. The mechanisms involved are probably other than those related to NO bioavailability. With better genetic knowledge, planning anesthesia with fewer side effects may be possible.

Vascular Functional Effect Mechanisms of Elabela in Rat Thoracic Aorta

BACKGROUND

Elabela is a recently discovered peptide hormone. The present study aims to investigate the vasorelaxant effect mechanisms of elabela in the rat thoracic aorta.

METHODS

The vascular rings obtained from the thoracic aortas of the male Wistar Albino rats were placed in the isolated tissue bath system. Resting tension was set to 1 gram. After the equilibration period, the vessel rings were contracted with phenylephrine or potassium chloride. Once a stable contraction was achieved, elabela-32 was applied cumulatively (10^-9 - 10^-6 molar) to the vascular rings. The experimental protocol was repeated in the presence of specific signaling pathway inhibitors or potassium channel blockers to determine the effect mechanisms of elabela.

RESULTS

Elabela showed a significant vasorelaxant effect in a concentration-dependent manner (p < 0.001). The vasorelaxant effect level of elabela was significantly reduced by the apelin receptor antagonist F13A, cyclooxygenase inhibitor indomethacin, adenosine monophosphate-activated protein kinase inhibitor dorsomorphin, protein kinase C inhibitor bisindolmaleimide, large-conductance calcium-activated potassium channel blocker iberiotoxin, and intermediate-conductance calcium-activated potassium channel blocker TRAM-34 (p < 0.001). However, the vasorelaxant effect level of elabela was not significantly affected by the endothelial nitric oxide synthase inhibitor nitro-L-arginine methyl ester and mitogen-activated protein kinase inhibitor U0126.

CONCLUSIONS

Elabela exhibits a prominent vasodilator effect in rat thoracic aorta. Apelin receptor, prostanoids, adenosine monophosphate-activated protein kinase, protein kinase C, and calcium-activated potassium channels are involved in the vasorelaxant effect mechanisms of elabela.

Gene-gene interactions in the protein kinase C/endothelial nitric oxide synthase axis impact the hypotensive effects of propofol

Anaesthesia with propofol is frequently associated with hypotension, which is at least partially attributable to increased nitric oxide (NO) formation derived from the activation of protein kinase C (PKC)/endothelial NO synthase (NOS3) axis. In this cross-sectional study, we tested whether PRKCA (which encodes PKCα) polymorphisms, or haplotypes, and interactions among PRKCA and NOS3 polymorphisms affect the hypotensive responses to propofol. We collected venous blood samples from 164 patients before and 10 min after propofol administration. Genotypes were determined by PCR and haplotype frequencies were estimated. Nitrite and NO_x (nitrites+nitrates) levels were measured by using an ozone-based chemiluminescence assay and the Griess reaction, respectively. We used multifactor dimensionality reduction to test interactions among PRKCA and NOS3 polymorphisms. Propofol promoted enhanced blood pressure-lowering effects and increased nitrite levels in subjects carrying GA + AA genotypes for the rs16960228 and TC + CC genotypes for the rs1010544 PRKCA polymorphisms, and the CCG haplotype. Moreover, genotypes for the rs1010544 PRKCA polymorphism were associated with higher or lower blood pressure decreases in response to propofol depending on the genotypes for the rs2070744 NOS3 polymorphism. Our findings suggest that PRKCA genotypes and haplotypes impact the hypotensive responses to propofol, possibly by modifying NO bioavailability, and that PRKCA-NOS3 interactions modify the blood pressure-lowering effects of propofol.

Arginase II polymorphisms modify the hypotensive responses to propofol by affecting nitric oxide bioavailability

PURPOSE

Propofol anesthesia is usually accompanied by hypotensive responses, which are at least in part mediated by nitric oxide (NO). Arginase I (ARG1) and arginase II (ARG2) compete with NO synthases for their common substrate L-arginine, therefore influencing the NO formation. We examined here whether ARG1 and ARG2 genotypes and haplotypes affect the changes in blood pressure and NO bioavailability in response to propofol.

METHODS

Venous blood samples were collected from 167 patients at baseline and after 10 min of anesthesia with propofol. Genotypes were determined by polymerase chain reaction. Nitrite concentrations were measured by using an ozone-based chemiluminescence assay, while NO_x (nitrites + nitrates) levels were determined by using the Griess reaction.

RESULTS

We found that patients carrying the AG + GG genotypes for the rs3742879 polymorphism in ARG2 gene and the ARG2 GC haplotype show lower increases in nitrite levels and lower decreases in blood pressure after propofol anesthesia. On the other hand, subjects carrying the variant genotypes for the rs10483801 polymorphism in ARG2 gene show more intense decreases in blood pressure (CA genotype) and/or higher increases in nitrite levels (CA and AA genotypes) in response to propofol.

CONCLUSION

Our results suggest that ARG2 variants affect the hypotensive responses to propofol, possibly by modifying NO bioavailability.

TRIAL REGISTRATION

NCT02442232.

Intermittent Hypoxia Augments Pulmonary Vasoconstrictor Reactivity through PKCβ/Mitochondrial Oxidant Signaling

Pulmonary vasoconstriction resulting from intermittent hypoxia (IH) contributes to pulmonary hypertension (pHTN) in patients with sleep apnea (SA), although the mechanisms involved remain poorly understood. Based on prior studies in patients with SA and animal models of SA, the objective of this study was to evaluate the role of PKCβ and mitochondrial reactive oxygen species (mitoROS) in mediating enhanced pulmonary vasoconstrictor reactivity after IH. We hypothesized that PKCβ mediates vasoconstriction through interaction with the scaffolding protein PICK1 (protein interacting with C kinase 1), activation of mitochondrial ATP-sensitive potassium channels (mitoK_ATP), and stimulated production of mitoROS. We further hypothesized that this signaling axis mediates enhanced vasoconstriction and pHTN after IH. Rats were exposed to IH or sham conditions (7 h/d, 4 wk). Chronic oral administration of the antioxidant Tempol or the PKCβ inhibitor LY-333531 abolished IH-induced increases in right ventricular systolic pressure and right ventricular hypertrophy. Furthermore, scavengers of O₂^- or mitoROS prevented enhanced PKCβ-dependent vasoconstrictor reactivity to endothelin-1 in pulmonary arteries from IH rats. In addition, this PKCβ/mitoROS signaling pathway could be stimulated by the PKC activator PMA in pulmonary arteries from control rats, and in both rat and human pulmonary arterial smooth muscle cells. These responses to PMA were attenuated by inhibition of mitoK_ATP or PICK1. Subcellular fractionation and proximity ligation assays further demonstrated that PKCβ acutely translocates to mitochondria upon stimulation and associates with PICK1. We conclude that a PKCβ/mitoROS signaling axis contributes to enhanced vasoconstriction and pHTN after IH. Furthermore, PKCβ mediates pulmonary vasoconstriction through interaction with PICK1, activation of mitoK_ATP, and subsequent mitoROS generation.

Transcriptome Analysis Reveals That Alfalfa Promotes Rumen Development Through Enhanced Metabolic Processes and Calcium Transduction in Hu Lambs

A healthy gut is very important for young animal development. The rumen of ruminants expands in size with the colonization of microbiota by 2 months of age. This process is promoted by alfalfa intervention. To elucidate the mechanism of this promotion, we performed transcriptomic analyses using a cohort of 23 lambs to evaluate the effects of starter diets plus alfalfa on the development of the rumen wall from the pre- to the postweaning period. The quantitative PCR analyses were used to validate selected genes that were differentially expressed in the transcriptome mapping. We found that several metabolic processes associated with rumen tissue development were affected by solid feed intake, with genes linked to the calcium signaling transduction pathway and the metabolism of pteridine-containing compounds and homocysteine metabolic process being upregulated in the group with alfalfa intervention. The results suggest that the pteridine-containing compounds and calcium signaling are targets for precise regulation of rumen development.

Propofol-induced vasodilation of mesenteric arterioles via BKCa channel and gap junction

The present study aimed to investigate the role of propofol in mediating the vasomotor activity of the mesenteric arteriole (MA) of Sprague Dawley (SD) rats, and to elucidate the underlying mechanisms. The pressure myograph technique was used to examine the effect of different concentrations of propofol on the relaxation of blood vessels in the 2–3 mm MA segments freshly separated from the SD rats. The whole-cell patch-clamp technique was applied to observe the outward current of single vascular smooth muscle cells (VSMCs) obtained from the MAs of the SD rats. Furthermore, immunofluorescence was utilized to assess the expression of connexin (Cx) in the MAs of SD rats. The results indicated the following: i) Propofol relaxed the MA of SD rats in a concentration-dependent manner from 1×10⁻⁷ to 3×10⁻⁴ mol/l; ii) in the acutely dissociated VSMCs, propofol (1×10⁻⁷ to 3×10⁻⁴ mol/l) enhanced the outward current of VSMCs in a concentration-dependent manner; iii) the enhanced outward currents induced by propofol (1×10⁻⁵ mol/l) may be reversed by tetraethylammonium (TEA; 1 mmol/l), a calcium-activated K⁺ channel inhibitor; iv) the effect of propofol on the relaxation of the vasculature wAS reduced after perfusion with 1 mmol/l TEA; v) Cx40, Cx43 and Cx45 were expressed on the MA; 6) 18β-glycyrrhetintic acid and 2-aminoethoxydiphenyl borate, two types of gap junction blocker, inhibited the propofol-induced relaxation. The present study provides evidence that propofol relaxes the MA, which may be associated with its effect of enhancing the channel current of large-conductance calcium voltage-activated potassium channels, contributing to the K⁺ outflow and leading to VSMC hyperpolarization; the gap junction may facilitate the hyperpolarization, which may lead to vascular synchronized relaxation and thereby reduce the blood pressure.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Endothelial nitric oxide synthase polymorphisms affect the changes in blood pressure and nitric oxide bioavailability induced by propofol

Propofol anesthesia is usually accompanied by hypotension, which is at least in part related to enhanced endothelial nitric oxide synthase (NOS3)-derived NO bioavailability. We examined here whether NOS3 polymorphisms (rs2070744, 4b/4a VNTR, rs3918226 and rs1799983) and haplotypes affect the changes in blood pressure and NO bioavailability induced by propofol. Venous blood samples were collected from 168 patients at baseline and after 10 min of anesthesia with propofol 2 mg/kg administered intravenously by bolus injection. Genotypes were determined by polymerase chain reaction and haplotype frequencies were estimated. Nitrite concentrations were measured by using an ozone-based chemiluminescence assay, while NOx (nitrites + nitrates) levels were determined by using the Griess reaction. We found that CT + TT genotypes for the rs3918226 polymorphism, the ba + aa genotypes for the 4b/4a VNTR and the CTbT haplotype were associated with lower decreases in blood pressure and lower increases in nitrite levels after propofol anesthesia. On the other hand, the TCbT and CCbT haplotypes were associated with more intense decreases in blood pressure and higher increases in nitrite levels in response to propofol. Our results suggest that NOS3 polymorphisms and haplotypes influence the hypotensive responses to propofol, possibly by affecting NO bioavailability.

Angiotensin converting enzyme inhibitors enhance the hypotensive effects of propofol by increasing nitric oxide production

Propofol anesthesia is usually accompanied by hypotension. Studies have shown that the hypotensive effects of propofol increase in patients treated with angiotensin-converting enzyme inhibitors (ACEi). Given that both propofol and ACEi affect nitric oxide (NO) signaling, the present study tested the hypothesis that ACEi treatment induces pronounced hypotensive responses to propofol by increasing NO bioavailability. In this study we evaluated 65 patients, divided into three groups: hypertensive patients chronically treated with ACEi (HT-ACEi; n = 21), hypertensive patients treated with other antihypertensive drugs instead of ACEi, such as angiotensin II receptor blockers, β-blockers or diuretics (HT; n = 21) and healthy normotensive subjects (NT; n = 23). Venous blood samples were collected at baseline and after 10min of anesthesia with propofol 2mg/kg administrated intravenously by bolus injection. Hemodynamic parameters were recorded at each blood sample collection. Nitrite levels were determined by using an ozone-based chemiluminescence assay, while NOx (nitrites+nitrates) levels were measured by using the Griess reaction. Additionally, experimental approaches were used to validate our clinical findings. Higher decreases in blood pressure after propofol anesthesia were observed in HT-ACEi group as compared with those found in NT and HT groups. Consistently, rats treated with the ACEi enalapril showed more intense hypotensive responses to propofol. The hypotensive effects of propofol were associated with increased NO production in both clinical and experimental approaches. Enhanced increases in nitrite levels after propofol anesthesia were observed in HT-ACEi patients compared with NT and HT groups. Accordingly, rats treated with enalapril showed increased vascular NO formation after propofol anesthesia compared with rats receiving vehicle. Our data show that ACEi enhance the hypotensive responses to propofol anesthesia and increase nitrite concentrations. These findings suggest that increased NO bioavailability may account for the enhanced hypotensive effects of propofol in ACEi-treated patients.

Propofol induces excessive vasodilation of aortic rings by inhibiting protein kinase Cβ2 and θ in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Exaggerated hypotension following administration of propofol is strongly predicted in patients with hypertension. Increased PKCs play a crucial role in regulating vascular tone. We studied whether propofol induces vasodilation by inhibiting increased PKC activity in spontaneously hypertensive rats (SHRs) and, if so, whether contractile Ca²⁺ sensitization pathways and filamentous-globular (F/G) actin dynamics were involved.

EXPERIMENTAL APPROACH

Rings of thoracic aorta, denuded of endothelium, from normotensive Wistar-Kyoto (WKY) rats and SHR were prepared for functional studies. Expression and activity of PKCs in vascular smooth muscle (VSM) cells were determined by Western blot analysis and elisa respectively. Phosphorylation of the key proteins in PKC Ca²⁺ sensitization pathways was also examined. Actin polymerization was evaluated by differential centrifugation to probe G- and F-actin content.

KEY RESULTS

Basal expression and activity of PKCβ2 and PKCθ were increased in aortic VSMs of SHR, compared with those from WKY rats. Vasorelaxation of SHR aortas by propofol was markedly attenuated by LY333531 (a specific PKCβ inhibitor) or the PKCθ pseudo-substrate inhibitor. Furthermore, noradrenaline-enhanced phosphorylation, and the translocation of PKCβ2 and PKCθ, was inhibited by propofol, with decreased actin polymerization and PKCβ2-mediated Ca²⁺ sensitization pathway in SHR aortas.

CONCLUSION AND IMPLICATIONS

Propofol suppressed increased PKCβ2 and PKCθ activity, which was partly responsible for exaggerated vasodilation in SHR. This suppression results in inhibition of actin polymerization, as well as that of the PKCβ2- but not PKCθ-mediated, Ca²⁺ sensitization pathway. These data provide a novel explanation for the unwanted side effects of propofol.

Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders

Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.

Quinapril decreases antifibrinolytic and prooxidative potential of propofol in arterial thrombosis in hypertensive rats

Angiotensin converting enzyme inhibitors and propofol both exert hypotensive action and may affect hemostasis. We investigated the influence of quinapril and propofol on hemodynamics and hemostasis in renal-hypertensive rats with induced arterial thrombosis. Two-kidney, one clip hypertensive rats were treated with quinapril (3.0 mg/kg for 10 days), and then received propofol infusion (15 mg/kg/h) during ongoing arterial thrombosis. The hemodynamic and hemostatic parameters were assayed. Quinapril exerted a hypotensive effect increasing after propofol infusion. Quinapril showed an antithrombotic effect with the platelet adhesion reduction, fibrinolysis enhancement and oxidative stress reduction. Propofol did not influence thrombosis; however, it inhibited fibrinolysis and showed prooxidative action. The effect of propofol on fibrinolysis and oxidative stress was significantly lower in quinapril-pretreated rats. Mortality was increased among rats treated with both drugs together. Our study demonstrates that pretreatment with quinapril reduced the adverse effects of propofol on hemostasis. Unfortunately, co-administration of both drugs potentiated hypotension in rats, which corresponds to higher mortality.

Pseudomonas aeruginosa Activates PKC-Alpha to Invade Middle Ear Epithelial Cells

Otitis media (OM) is a group of complex inflammatory disorders affecting the middle ear which can be acute or chronic. Chronic suppurative otitis media (CSOM) is a form of chronic OM characterized by tympanic membrane perforation and discharge. Despite the significant impact of CSOM on human population, it is still an understudied and unexplored research area. CSOM is a leading cause of hearing loss and life-threatening central nervous system complications. Bacterial exposure especially Pseudomonas aeruginosa is the most common cause of CSOM. Our previous studies have demonstrated that P. aeruginosa invades human middle ear epithelial cells (HMEECs). However, molecular mechanisms leading to bacterial invasion of HMEECs are not known. The aim of this study is to characterize the role of PKC pathway in the ability of P. aeruginosa to colonize HMEECs. We observed that otopathogenic P. aeruginosa activates the PKC pathway, specifically phosphorylation of PKC-alpha (PKC-α) in HMEECs. The ability of otopathogenic P. aeruginosa to phosphorylate PKC-α depends on bacterial OprF expression. The activation of PKC-α was associated with actin condensation. Blocking the PKC pathway attenuated the ability of bacteria to invade HMEECs and subsequent actin condensation. This study, for the first time, demonstrates that the host PKC-α pathway is involved in invasion of HMEECs by P. aeruginosa and subsequently to cause OM. Characterizing the role of the host signaling pathway in the pathogenesis of CSOM will provide novel avenues to design effective treatment modalities against the disease.