Thromboxane Synthetase Research Articles

Progress in Xenogeneic Lung Transplantation Using Multi-Transgenic Donor Pigs and Targeted Supportive Drug Treatments

Purpose Significant progress in genetic engineering has enabled the generation of knock-out pigs that additionally express multiple human “transgenes” chosen to address various known xenogeneic rejection pathways. We evaluated which transgene combinations are associated with prevention of lung xenograft injury in a rigorous life-supporting pig-to-baboon lung xenograft model. Methods GTKO.hCD46 porcine donor organs with up to 4 additional genetic modifications, including hCD55, hTBM, hEPCR, hTFPI, hCD47, hCD39, hHO-1, HLA-E, A20 and humanized vWF were used in 48 left single lung transplants into baboons. A rationally designed “platform drug regimen” consisted of steroids, sC1Inh, thromboxane synthase inhibitor, histamine receptor blockers, and anti-GPIb Fab. Desmopressin (DDAVP) was given to the donor animals prior to lung procurement, to deplete pig endothelial VWF. Immunosuppression consisted of aCD20, ATG, MMF, aCD40, coupled with anti-IL6R moAb and/or Alpha-1 Antitrypsin. Xenograft function was assessed intermittently by transplant blood flow measurements and radiographs. Results Xenogeneic lungs with 6 genetic modifications (6-GE) transplanted into baboons survived for up to 8d (hCD55.hEPCR.hTBM.hCD39) and 9d (hEPCR.hTBM.hCD47.HO-1), vs <12hrs for most 3- or 4-GE lungs. Several other donor transgene-combinations resulted in 47d survival. Lungs of GTKO.hCD46.hCD55.hEPCR.hCD47.hTFPI and a few 3- or 4-GE phenotypes (eg including HLA-E and hvWF) consistently exhibited life-supporting (LS) lung function for 24-30h, with relatively normal macro- and microscopic lung appearance until 2-3 d. Lung xenograft failure was usually associated with rebounding anti-pig antibody titer and loss of lung vascular barrier function leading to alveolar flooding and consolidation, consistent with “delayed xenograft rejection”. Accumulated evidence suggests that, in addition to anti-non-Gal antibody, recipient NK cells (HLA-E) and donor macrophage activation (thromboxane) each play important roles to drive the residual inflammation. Conclusion Combining multi-transgenic donor organs with mechanism-directed drug treatments significantly prolongs life-supportive lung xenograft function and recipient survival. Aggregation of existing targeted genetic modifications, along with antibody depletion and mechanism-based drug additions appear likely to successfully control known pathogenic pathways, and further advance lung xenotransplantation towards clinical application. United Therapeutics SRA. NIH U19A1090959.

Pharmacokinetic–pharmacodynamic modeling to study the anti-dysmenorrhea effect of Guizhi Fuling capsule on primary dysmenorrhea rats

BackgroundPrimary dysmenorrhea (PDM) is one of the most common gynaecological disorders among women, which seriously affects women's life quality due to its high incidence rate. Guizhi Fuling capsule (GZFLC), a well-known traditional Chinese medical prescription, has been widely used to treat gynecological blood stasis syndromes such as PDM. However, its mechanisms of action and combination were still unknown. PurposeThe aim of this study was to develop a pharmacokinetic–pharmacodynamic (PK-PD) model to assess time-concentration-effect relationships for anti-dysmenorrhea effect of GZFLC and provide better understanding for mechanisms of action and combination of GZFLC. Study design and methodsThe PDM rats model was induced by oxytocin exposure following estradiol benzoate pretreatment. Gallic acid (GA), amygdalin (AMY), albiflorin (ALB), prunasin (PA) and cinnamic acid (CA) were evaluated as bioactive ingredients for investigating PK processes. GA, AMY, ALB and PA exhibited appropriate PK parameters and were selected as the PK markers to map the anti-dysmenorrhea effect of GZFLC. A PK-PD model was established on the basis of GA, AMY, ALB and PA plasma concentrations vs. the values of two ratios (PGE2/PGF2α and 6-Keto-PGF1α/TXB2), by a two-compartment PK model with a simple Emax model to explain the time delay between the drug plasma concentrations of PK markers and the anti-dysmenorrhea effect. ResultsThe PDM rat model has been successfully established. Compared with the normal treated group, the bioactive ingredients in PDM treated group exhibited significant changing trends of PK behaviors, such as better absorption and distribution, slower elimination and delays in reaching the maximum concentration (Tmax). The analysis of PK-PD parameters indicated that the active metabolites and prototypes of bioactive ingredients in GZFLC were inclined to regulate the activity of prostacyclin synthetase and thromboxane synthetase to control the production of TXA2 and PGI2 so as to treat PDM. As the main effective medicinal materials for the treatment of PDM in GZFLC prescription Persicae Semen, Moutan Cortex and Paeonia lactiflora Pall, Persicae Semen played the most important role, while the role of Paeonia lactiflora Pall was the weakest. ConclusionThe PK-PD model results provided scientific basis for clarifying compatibility mechanisms of GZFLC prescription and a better understanding for biosynthetic mechanisms of four prostaglandins (PGE2, PGF2α, 6-Keto-PGF1α and TXB2) in the treatment of PDM by GZFLC. Investigations on the relationship between the effects and the bioactive ingredients are of benefit to explore the mechanisms of action and combination for traditional Chinese medical prescriptions (TCP) and facilitate the development of future clinical applications of TCP.

L‐arginine Supplementation and Thromboxane Synthase Inhibition Reverse Cerebral Ischemia in Murine Cerebral Malaria by Plasmodium berghei ANKA

Cerebral malaria (CM) is one of the most severe and lethal complications of Plasmodium falciparum infection. The mainstay treatment for CM is intravenous artesunate, nevertheless 15–20% of the patients receiving this drug still die. Vascular dysfunction, with vasoconstriction, leads to decreased cerebral blood flow, ischemia, tissue hypoxia and death in CM. Nitric oxide (NO) and arachidonic acid metabolites are important regulators of physiological cerebral blood flow through their vasodilator or vasoconstrictive properties. The objective of this study was to determine the effects of L‐arginine supplementation and pharmacological inhibition of thromboxane A2 (TXA2) synthesis on the reversal of ischemia in experimental cerebral malaria (ECM). C57BL/6 mice infected with Plasmodium berghei ANKA (PbA) and showing clinical signs of ECM were treated subcutaneously with the NO precursor L‐arginine (50mg/kg) and/or the thromboxane synthase inhibitor ozagrel (100mg/kg). Cerebral blood flow was measured by Laser Speckle Contrast Imaging (LSCI). The adjuvant effect of L‐arginine in combination with artesunate on survival of mice with late‐stage ECM was evaluated. Animals that developed ECM showed a significant decrease (25%) in cerebral blood flow compared to non‐infected control animals. L‐arginine induced a marked increase (22.5%) in cerebral blood flow in mice with ECM one hour after administration. The administration of ozagrel, which prevents the generation of the vasoconstrictor metabolite TXA2, also led to increased (16.5%) cerebral blood flow in animals with ECM, and this was consistent with decreased levels of brain TXA2 in ozagrel‐treated compared to saline‐treated animals. The combination of ozagrel and L‐arginine showed no synergistic effect on cerebral blood flow. Treatment of animals with late‐stage ECM with artesunate plus L‐arginine increased survival compared to artesunate plus saline. Conclusion: L‐arginine and ozagrel increase cerebral blood flow, and L‐arginine increase survival in mice with cerebral malaria and show potential as adjuvant therapy for this malaria complication.Support or Funding InformationCAPES, FAPERJ, IOC‐FiocruzThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Uridine Adenosine Tetraphosphate-Induced Coronary Relaxation Is Blunted in Swine With Pressure Overload: A Role for Vasoconstrictor Prostanoids

Plasma levels of the vasoactive substance uridine adenosine tetraphosphate (Up4A) are elevated in hypertensive patients and Up4A-induced vascular contraction is exacerbated in various arteries isolated from hypertensive animals, suggesting a potential role of Up4A in development of hypertension. We previously demonstrated that Up4A produced potent and partially endothelium-dependent relaxation in the porcine coronary microvasculature. Since pressure-overload is accompanied by structural abnormalities in the coronary microvasculature as well as by endothelial dysfunction, we hypothesized that pressure-overload blunts the coronary vasodilator response to Up4A, and that the involvement of purinergic receptors and endothelium-derived factors is altered. The effects of Up4A were investigated using wire-myography in isolated coronary small arteries from Sham-operated swine and swine with prolonged (8 weeks) pressure overload of the left ventricle induced by aortic banding (AoB). Expression of purinergic receptors and endothelium-derived factors was assessed in isolated coronary small arteries using real-time PCR. Up4A (10-9 to 10-5 M) failed to produce contraction in isolated coronary small arteries from either Sham or AoB swine, but produced relaxation in preconstricted arteries, which was significantly blunted in AoB compared to Sham. Blockade of purinergic P1, and P2 receptors attenuated Up4A-induced coronary relaxation more, while the effect of P2X1-blockade was similar and the effects of A2A- and P2Y1-blockade were reduced in AoB as compared to Sham. mRNA expression of neither A1, A2, A3, nor P2X1, P2X7, P2Y1, P2Y2, nor P2Y6-receptors was altered in AoB as compared to Sham, while P2Y12 expression was higher in AoB. eNOS inhibition attenuated Up4A-induced coronary relaxation in both Sham and AoB. Additional blockade of cyclooxygenase enhanced Up4A-induced coronary relaxation in AoB but not Sham swine, suggesting the involvement of vasoconstrictor prostanoids. In endothelium-denuded coronary small arteries from normal swine, thromboxane synthase (TxS) inhibition enhanced relaxation to Up4A compared to endothelium-intact arteries, to a similar extent as P2Y12 inhibition, while the combination inhibition of P2Y12 and TxS had no additional effect. In conclusion, Up4A-induced coronary relaxation is blunted in swine with AoB, which appears to be due to the production of a vasoconstrictor prostanoid, likely thromboxane A2.

LIGAND-BINDING AND CATALYTIC PROPERTIES OF RECOMBINANT HUMAN THROMBOXANE SYNTHASE

To study the spectrum of modulators of the human thromboxane synthase activity, the interaction of recombinant protein with various low-molecular weight ligands was analyzed. It was shown that thromboxane synthase interacts with a number of fatty acids and their derivatives (potential substrates or concurrent inhibitors), being a target for nonselective inhibition by imidazole and triazole derivatives used in medical practice and agriculture. Thus, another mechanism of action of endocrine-disrupting chemicals (EDC) was established. For the first time, the reduction of heme iron of thromboxane synthase by cytochrome P450 reductase was shown. This interaction accompanied by a partial inhibitory effect on the enzyme suppresses the formation of reaction by-products 12-hydroxyheptadecatenoic acid (12-HHT) and malonic dialdehyde (MDA). It is likely that this mechanism can participate in the regulation of the enzyme activity in vivo.

Increased Levels of Txa₂ Induced by Dengue Virus Infection in IgM Positive Individuals Is Related to the Mild Symptoms of Dengue.

The inflammatory process plays a major role in the prognosis of dengue. In this context, the eicosanoids may have considerable influence on the regulation of the Dengue virus-induced inflammatory process. To quantify the molecules involved in the cyclooxygenase and lipoxygenase pathways during Dengue virus infection, plasma levels of thromboxane A2, prostaglandin E2 and leukotriene B4; mRNA levels of thromboxane A2 synthase, prostaglandin E2 synthase, leukotriene A4 hydrolase, cyclooxygenase-2 and 5-lipoxygenase; and the levels of lipid bodies in peripheral blood leukocytes collected from IgM-positive and IgM-negative volunteers with mild dengue, and non-infected volunteers, were evaluated. Dengue virus infection increases the levels of thromboxane A2 in IgM-positive individuals as well as the amount of lipid bodies in monocytes in IgM-negative individuals. We suggest that increased levels of thromboxane A2 in IgM-positive individuals plays a protective role against the development of severe symptoms of dengue, such as vascular leakage.

9-(4'-dimethylaminophenyl)-2,6,7-trihydroxy-xanthene-3-one is a Potentially Novel Antiplatelet Drug which Antagonizes the Effect of Thromboxane A2.

Currently, used oral antiplatelet drugs are both limited and associated with the risk of treatment failure/resistance. Research in this area is hence highly desired. A series of xanthene-3-ones derivatives, we had synthesized, showed us that these derivatives had antiplatelet activity. As far as we know, no research on the effects of xanthen-3-ones in this area has been done. The aim was to study the antiplatelet potential of a series of synthesised 9-phenylxanthene- 3-ones and to find the ideal structural feature(s) for antiplatelet potential and determine the mechanism of action. The compounds were synthesized from 1,2,4-triacetoxybenzene and various benzaldehydes. The reaction proceeded smoothly under acidic alcoholic conditions, furnishing the desired products in good yields. The compounds were first screened in whole human blood where platelet aggregation was induced by arachidonic acid. Further analysis was targeted at search of the mechanism of action. Initial screening showed that a majority of the synthesized derivatives had substantial antiplatelet potential. None of the compounds were able to block cyclooxygenase 1 or thromboxane synthase. The mechanism appeared to be based on antagonism of thromboxane effects. The most potent compound 9-(4'-dimethylaminophenyl)-2,6,7-trihydroxy-xanthene-3-one had better potential to block collagen induced platelet aggregation than clinically used acetylsalicylic acid. The last mentioned derivative is promising for further in vivo testing.

ApoL1 renal risk variants induce aberrant THP-1 monocyte differentiation and increase eicosanoid production via enhanced expression of cyclooxygenase-2.

Apolipoprotein L1 ( ApoL1) genetic variants are strongly associated with kidney diseases. We investigated the role of ApoL1 variants in monocyte differentiation and eicosanoid production in macrophages, as activated tissue macrophages in kidney might contribute to kidney injury. In human monocyte THP-1 cells, transient overexpression of ApoL1 (G0, G1, G2) by transfection resulted in a 5- to 11-fold increase in CD14 and CD68 gene expression, similar to that seen with phorbol-12-myristate acetate treatment. All ApoL1 variants caused monocytes to differentiate into atypical M1 macrophages with marked increase in M1 markers CD80, TNF, IL1B, and IL6 and modest increase in the M2 marker CD163 compared with control cells. ApoL1-G1 transfection induced additional CD206 and TGFB1 expression, and ApoL1-G2 transfection induced additional CD204 and TGFB1 expression. Gene expression of prostaglandin E2 (PGE2) synthase and thromboxane synthase and both gene and protein expression of cyclooxygenase-2 (COX-2) were increased by ApoL1-G1 and -G2 variants compared with -G0 transfection. Higher levels of PGE2 and thromboxane B2, a stable metabolite of thromboxane A2, and transforming growth factor (TGF)-β1 were released into the supernatant of cultured THP-1 cells transfected with ApoL1-G1 and -G2, but not -G0. The increase in PGE2, thromboxane B2, and TGF-β1 was inhibited by COX-2-specific inhibitor CAY10404 but not by COX-1-specific inhibitor SC-560. These results demonstrate a novel role of ApoL1 variants in the regulation of monocyte differentiation and eicosanoid metabolism, which could modify the immune response and promote inflammatory signaling within the local targeted organs and tissues including the kidney.

Inhibitory effects of thromboxane A2 generation by ginsenoside Ro due to attenuation of cytosolic phospholipase A2 phosphorylation and arachidonic acid release

BackgroundThromboxane A2 (TXA2) induces platelet aggregation and promotes thrombus formation. Although ginsenoside Ro (G-Ro) from Panax ginseng is known to exhibit a Ca2+-antagonistic antiplatelet effect, whether it inhibits Ca2+-dependent cytosolic phospholipase A2 (cPLA2α) activity to prevent the release of arachidonic acid (AA), a TXA2 precursor, is unknown. In this study, we attempted to identify the mechanism underlying G-Ro-mediated TXA2 inhibition. MethodsWe investigated whether G-Ro attenuates TXA2 production and its associated molecules, such as cyclooxygenase-1 (COX-1), TXA2 synthase (TXAS), cPLA2α, mitogen-activated protein kinases, and AA. To assay COX-1 and TXAS, we used microsomal fraction of platelets. ResultsG-Ro reduced TXA2 production by inhibiting AA release. It acted by decreasing the phosphorylation of cPLA2α, p38-mitogen-activated protein kinase, and c-Jun N-terminal kinase1, rather than by inhibiting COX-1 and TXAS in thrombin-activated human platelets. ConclusionG-Ro inhibits AA release to attenuate TXA2 production, which may counteract TXA2-associated thrombosis.

Regulator of calcineurin 1 modulates vascular contractility and stiffness through the upregulation of COX-2-derived prostanoids

Cyclooxygenase-2 (COX-2) derived-prostanoids participate in the altered vascular function and mechanical properties in cardiovascular diseases. We investigated whether regulator of calcineurin 1 (Rcan1) participates in vascular contractility and stiffness through the regulation of COX-2. For this, wild type (Rcan1+/+) and Rcan1-deficient (Rcan1−/−) mice untreated or treated with the COX-2 inhibitor rofecoxib were used. Vascular function and structure were analysed by myography. COX-2 and phospo-p65 expression were studied by western blotting and immunohistochemistry and TXA2 production by ELISA. We found that Rcan1 deficiency increases COX-2 and IL-6 expression and NF-κB activation in arteries and vascular smooth muscle cells (VSMC). Adenoviral-mediated re-expression of Rcan1.4 in Rcan1−/− VSMC normalized COX-2 expression. Phenylephrine-induced vasoconstrictor responses were greater in aorta from Rcan1−/− compared to Rcan1+/+ mice. This increased response were diminished by etoricoxib, furegrelate, SQ 29548, cyclosporine A and parthenolide, inhibitors of COX-2, TXA2 synthase, TP receptors, calcineurin and NF-κB, respectively. Endothelial removal and NOS inhibition increased phenylephrine responses only in Rcan1+/+ mice. TXA2 levels were greater in Rcan1−/− mice. In small mesenteric arteries, vascular function and structure were similar in both groups of mice; however, vessels from Rcan1−/− mice displayed an increase in vascular stiffness that was diminished by rofecoxib. In conclusion, our results suggest that Rcan1 might act as endogenous negative modulator of COX-2 expression and activity by inhibiting calcineurin and NF-kB pathways to maintain normal contractility and vascular stiffness in aorta and small mesenteric arteries, respectively. Our results uncover a new role for Rcan1 in vascular contractility and mechanical properties.

Associations between thromboxane A synthase 1 gene polymorphisms and the risk of ischemic stroke in a Chinese Han population.

Thromboxane A synthase 1 (TBXAS1) catalyses the synthesis of thromboxane A2 (TXA2), which plays an important role in the pathogenesis of ischemic stroke. Thus, the TBXAS1 gene was investigated as a candidate gene involved in the formation of atherosclerosis. This case-control study collected peripheral blood specimens and clinical data of 370 ischemic stroke patients and 340 healthy controls in the Northern Chinese Han population from October 2010 to May 2011. Two TBXAS1 single-nucleotide polymorphisms, rs2267682 and rs10487667, were analyzed using a SNaPshot Multiplex sequencing assay to explore the relationships between the single-nucleotide polymorphisms in TBXAS1 and ischemic stroke. The TT genotype frequency and T allele frequency of rs2267682 in the patients with ischemic stroke were significantly higher than those in the controls (P < 0.01 and P = 0.02). Furthermore, compared with the GG + GT genotype, the TT rs2267682 genotype was associated with increased risk of ischemic stroke (odds ratio (OR) = 1.80, 95% confidence interval (CI): 1.16-2.79, P < 0.01). Multivariate logistic analysis with adjustments for confounding factors revealed that rs2267682 was still associated with ischemic stroke (OR = 1.94, 95% CI : 1.13-3.33, P = 0.02). The frequency of the T-G haplotype in the patients was significantly higher than that in the controls according haplotype analysis (OR = 1.49, 95% CI: 1.10-2.00, P < 0.01). These data reveal that the rs2267682 TBXAS1 polymorphism is associated with ischemic stroke. The TT genotype of TBXAS1 and T allele of rs2267682 increase susceptibility to ischemic stroke in this Northern Chinese Han population. The protocol has been registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559).

ASPIRIN RESISTANCE AS A RISK MARKER FOR VENOUS THROMBOEMBOLIC COMPLICATIONS

The possible mechanisms for the development of aspirin resistance, platelet involvement in thrombus formation, inflammation and atherogenesisare presented. The presence of associations between aspirin resistance and the risk of thrombotic complications in people not using aspirin and the possibility of using aspirin resistance to assess the individual risk of thromboembolic complications in 492 patients (mean age 56.2 ± 0.9 years) with arterial hypertension I - Stage II and without ithas been researched. The parameters of platelet aggregation were studied in subgroups of patients different in the risk of developing venous thrombo-embolic complications by reaction to the cyclooxygenase blocker. It has been revealed that the conducted antiplatelet therapy is effective in 50-60 % of persons with cardiovascular diseases; ~ 40 % of patients show signs of relative resistance to antiplatelet agents. Resistance to therapeutic doses of antiplatelet agents is multifactorial, however, the presence of a shunt between thromboxane synthetase and lipoxygenase plays a role in it. It is likely that the influence of inflammation on the development of aspirin resistance through an increase in the synthesis of 12-NETU, thromboxane and leukotrienes. Aspirin resistance is a risk factor for the development of venous thrombotic complications, regardless of the use of antiaggregant therapy. It was established that the most accurate prediction of the result according to the severity of hemorheological disorders (distinguishing between moderate and severe disorders from the lungs) is provided by such indicators of platelet aggregation as the coefficient K ((ADF5 % - ADP 5 % + Asp) - 100 / ADF 5 %) (AUC 0.995) and ADP 5 % (AUC 0.713). Changes in platelet aggregation in response to aspirin in an in vitro test can be used to identify individuals with a high risk of thrombotic complications, and to assess individual risk (specificity 92.9-98.2 %, sensitivity 83.7-93 %).

Direct Molecular Fishing of New Protein Partners for Human Thromboxane Synthase

Thromboxane synthase (TBXAS1) catalyzes the isomerization reaction of prostaglandin H2 producing thromboxane A2, the autocrine and paracrine factor in many cell types. A high activity and metastability by these arachidonic acid derivatives suggests the existence of supramolecular structures that are involved in the regulation of the biosynthesis and directed translocation of thromboxane to the receptor. The objective of this study was to identify TBXAS1 protein partners from human liver tissue lysate using a complex approach based on the direct molecular fishing technique, LC-MS/MS protein identification, and protein-protein interaction validation by surface plasmon resonance (SPR). As a result, 12 potential TBXAS1 protein partners were identified, including the components regulating cytoskeleton organization (BBIP1 and ANKMY1), components of the coagulation cascade of human blood (SERPINA1, SERPINA3, APOH, FGA, and FN1), and the enzyme involved in the metabolism of xenobiotics and endogenous bioregulators (CYP2E1). SPR validation on the Biacore 3000 biosensor confirmed the effectiveness of the interaction between CYP2E1 (the enzyme that converts prostaglandin H2 to 12-HHT/thromboxane A2 proantagonist) and TBXAS1 (Kd = (4.3 0.4) 10-7 M). Importantly, the TBXAS1CYP2E1 complex formation increases fivefold in the presence of isatin (indole-2,3-dione, a low-molecular nonpeptide endogenous bioregulator, a product of CYP2E1). These results suggest that the interaction between these hemoproteins is important in the regulation of the biosynthesis of eicosanoids.

Homology Modeling and Molecular Dynamics Simulation Combined with X-ray Solution Scattering Defining Protein Structures of Thromboxane and Prostacyclin Synthases.

A combination of molecular dynamics (MD) simulations and X-ray scattering (SAXS) has emerged as the approach of choice for studying protein structures and dynamics in solution. This approach has potential applications for membrane proteins that neither are soluble nor form crystals easily. We explore the water-coupled dynamic structures of thromboxane synthase (TXAS) and prostacyclin synthase (PGIS) from scanning HPLC-SAXS measurements combined with MD ensemble analyses. Both proteins are heme-containing enzymes in the cytochrome P450 family, known as prostaglandin H2 (PGH2) isomerase, with counter-functions in regulation of platelet aggregation. Currently, the X-ray crystallographic structures of PGIS are available, but those for TXAS are not. The use of homology modeling of the TXAS structure with ns-μs explicit water solvation MD simulations allows much more accurate estimation of the configuration space with loop motion and origin of the protein behaviors in solution. In contrast to the stability of the conserved PGIS structure in solution, the pronounced TXAS flexibility has been revealed to have unstructured loop regions in connection with the characteristic P450 structural elements. The MD-derived and experimental-solution SAXS results are in excellent agreement. The significant protein internal motions, whole-molecule structures, and potential problems with protein folding, crystallization, and functionality are examined.

Lung xenotransplantation.

This review describes the most recent progress in xeno lung transplantation (XLTx) to date. It describes the potential mechanisms of early xeno lung graft loss, as well as the latest therapeutic strategies to overcome them. Using ex-vivo perfusion models of porcine lungs with human blood, the use of genetically modified pig lungs along with novel pharmaceutical approaches has recently been studied. Strategies that have demonstrated improved lung survival include the knockout of known xenoantigens (GalTKO and N-glycolylneuraminic acid-KO), genes that regulate complement activation (hCD46 and hCD55), as well as the inflammation/coagulation cascade (human leukocyte antigen-E, human thrombomodulin, human endothelial protein C receptor, hCD47, hCD39, hCD73 and heme oxygenase-1). Furthermore, pharmacologic interventions including the depletion of pulmonary intravascular macrophages or von Willebrand factor, inhibition of thromboxane synthase and blockade of histamine receptors have also demonstrated protective effects on xeno lung grafts. Using in-vivo pig to nonhuman primate lung transplant models, these approaches have been shown to extend pulmonary xenograft survival to 5 days. The development of new multitransgenic GalTKO pigs has demonstrated prolongation of porcine xenograft survival; however, advancement in XLTx has remained frustratingly limited. Further intensive and innovative strategies including genetic manipulation of donors, as well as inflammation/coagulation dysregulation, are required to make XLTx a clinical possibility.

Прямой молекулярный фишинг новых белков-партнеров тромбоксансинтазы человека

Прямой молекулярный фишинг новых белков-партнеров тромбоксансинтазы человека

Прямой молекулярный фишинг новых белков-партнеров тромбоксансинтазы человека

Thromboxane synthase (TBXAS1) catalyzes the isomerization reaction of prostaglandin H2 producing thromboxane A2, the autocrine and paracrine factor in many cell types. A high activity and metastability by these arachidonic acid derivatives suggests the existence of supramolecular structures that are involved in the regulation of the biosynthesis and directed translocation of thromboxane to the receptor. The objective of this study was to identify TBXAS1 protein partners from human liver tissue lysate using a complex approach based on the direct molecular fishing technique, LC-MS/MS protein identification, and protein-protein interaction validation by surface plasmon resonance (SPR). As a result, 12 potential TBXAS1 protein partners were identified, including the components regulating cytoskeleton organization (BBIP1 and ANKMY1), components of the coagulation cascade of human blood (SERPINA1, SERPINA3, APOH, FGA, and FN1), and the enzyme involved in the metabolism of xenobiotics and endogenous bioregulators (CYP2E1). SPR validation on the Biacore 3000 biosensor confirmed the effectiveness of the interaction between CYP2E1 (the enzyme that converts prostaglandin H2 to 12-HHT/thromboxane A2 proantagonist) and TBXAS1 (Kd = (4.3 ± 0.4) × 10-7 M). Importantly, the TBXAS1•CYP2E1 complex formation increases fivefold in the presence of isatin (indole-2,3-dione, a low-molecular nonpeptide endogenous bioregulator, a product of CYP2E1). These results suggest that the interaction between these hemoproteins is important in the regulation of the biosynthesis of eicosanoids.

Mercury exposure induces proinflammatory enzymes in vascular fibroblasts

IntroductionPrevious studies show that mercury exposure increases cardiovascular risk, although the underlying cellular mechanisms have still not been fully studied. The aim of this project is to study, in vascular fibroblasts (VF), the effect of HgCl2 exposure on the expression of enzymes involved in the synthesis of prostanoids and reactive oxygen species (ROS). These molecules have been shown to participate in the inflammatory response associated with cardiovascular diseases. Material and methodsAdventitial VF cultures of Sprague-Dawley rat aortas, shown to be α-actin negative by immunofluorescence, were exposed to HgCl2 (0.05–5μg/mL) for 48h. mRNA and protein levels of cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase 1 (mPGES-1), thromboxane A2 synthase (TXAS), NADPH oxidase 1 (NOX-1), and 4 (NOX-4) where analyzed using qRT-PCR and western blot, respectively. NOX activity was determined by chemiluminescence. ResultsHgCl2 exposure increased COX-2, mPGES-1, TXAS, and NOX-1 expression and NOX activity, and decreased NOX-4 expression. The increase in NOX-1 and COX-2 expression was abolished by the treatment with inhibitors of COX-2 (10μM celecoxib) and NOX (300μM apocynin, 0.5μM ML-171). Conclusions1) HgCl2 increases the expression of pro-inflammatory enzymes involved in ROS and prostanoid synthesis in VF. 2) There is a reciprocal regulation between COX-2 and NOX-1 pathways. 3) These effects can contribute to explain the increase in cardiovascular risk associated to mercury.

Involvement of thromboxane A2 in interleukin-31-induced itch-associated response in mice.

Atopic dermatitis is a chronic and severe pruritic skin disease. Interlukin-31 (IL-31) has been recently demonstrated to be one of the key pruritogens in atopic dermatitis. However, the mechanisms underlying IL-31-induced itching remains unclear. In our previous study, we have shown that thromboxane (TX) A2 is involved in itch-associated responses in mice with atopy-like skin diseases. IL-31 was given intradermally into the rostral back of ICR mice and the hind-paw scratching to the injection site were counted. Expression of TX synthase and IL-31 receptors were analyzed using immunohistochemical staining or RT-PCR in mouse skin or primary cultures of mouse keratinocytes. The concentration of TXB2, a metabolite of TXA2, in the skin and the culture medium of primary cultures of mouse keratinocytes was measured using enzyme immunoassay. The concentration of intracellular Ca2+ ions in mouse keratinocytes was measured using the calcium imaging method. An intradermal injection of IL-31 elicited scratching, an itch-related response, in mice. The scratching was inhibited by TP TXA2 receptor antagonist DCHCH. The distribution of TX synthase and IL-31RA receptor was mainly epidermal keratinocytes in the skin. The primary cultures of keratinocytes expressed the mRNAs of TX synthase and IL-31 receptors. IL-31 increased the concentration of TXB2, which was inhibited by TX synthase inhibitor sodium ozagrel and EGTA, in the skin and the culture medium of primary cultures of keratinocytes. IL-31 increased the concentration of intracellular Ca2+ ions in mouse keratinocytes. It is suggested that IL-31 elicits itch-associated responses through TXA2 produced from keratinocytes.

N-glycolylneuraminic acid knockout reduces erythrocyte sequestration and thromboxane elaboration in an ex vivo pig-to-human xenoperfusion model.

Wild-type pigs express several carbohydrate moieties on their cell surfaces that differ from those expressed by humans. This difference in profile leads to pig tissue cell recognition of human blood cells causing sequestration, in addition to antibody-mediated xenograft injury. One such carbohydrate is N-glycolylneuraminic acid (Neu5Gc), a sialic acid molecule synthesized in pigs but not in humans. Here, we evaluate livers with and without Neu5Gc in an ex vivo liver xeno perfusion model. Livers from pigs with an α1,3-galactosyl transferase gene knockout (GalTKO) and transgenic for human membrane cofactor (hCD46) with (n=5) or without (n=7) an additional Neu5Gc gene knock out (Neu5GcKO) were perfused ex vivo with heparinized whole human blood. A drug regimen consisting of a histamine inhibitor, thromboxane synthase inhibitor, and a murine anti-human GPIb-blocking antibody fragment was given to half of the experiments in each group. Liver function tests (AST and ALT) were not significantly different between livers with and without the Neu5GcKO. GalTKO.hCD46.Neu5GcKO livers had less erythrocyte sequestration as evidenced by a higher mean hematocrit over time compared to GalTKO.hCD46 livers (P=.0003). The addition of Neu5GcKO did not ameliorate profound thrombocytopenia seen within the first 15minutes of perfusion. TXB2 was significantly less with the added drug regimen (P=.006) or the presence of Neu5GcKO (P=.017). The lack of Neu5Gc expression attenuated erythrocyte loss but did not prevent profound early onset thrombocytopenia or platelet activation, although TXB2 levels were decreased in the presence of Neu5GcKO.