Change of plasma leukotriene C4 during myocardial ischemia in humans

The role of lipid-based signalling in wound healing and senescence

Lipid-based signalling modulates several cellular processes and intercellular communication during wound healing and tissue regeneration. Bioactive lipids include but are not limited to the diverse group of eicosanoids, phospholipids, and extracellular vesicles and mediate the attraction of immune cells, initiation of inflammatory responses, and their resolution. In aged individuals, wound healing and tissue regeneration are greatly impaired, resulting in a delayed healing process and non-healing wounds. Senescent cells accumulate with age in vivo, preferably at sites implicated in age-associated pathologies and their elimination was shown to alleviate many age-associated diseases and disorders. In contrast to these findings, the transient presence of senescent cells in the process of wound healing exerts beneficial effects and limits fibrosis. Hence, clearance of senescent cells during wound healing was repeatedly shown to delay wound closure in vivo. Recent findings established a dysregulated synthesis of eicosanoids, phospholipids and extracellular vesicles as part of the senescent phenotype. This intriguing connection between cellular senescence, lipid-based signalling, and the process of wound healing and tissue regeneration prompts us to compile the current knowledge in this review and propose future directions for investigation.

The leukotrienes: immune-modulating lipid mediators of disease

The leukotrienes are important lipid mediators with immune modulatory and proinflammatory properties. Classical bioactions of leukotrienes include chemotaxis, endothelial adherence, and activation of leukocytes, chemokine production, as well as contraction of smooth muscles in the microcirculation and respiratory tract. When formed in excess, these compounds play a pathogenic role in several acute and chronic inflammatory diseases, such as asthma, rheumatoid arthritis, and inflammatory bowel disease. An increasing number of diseases have been linked to inflammation implicating the leukotrienes as potential mediators. For example, recent investigations using genetic, morphological, and biochemical approaches have pointed to the involvement of leukotrienes in cardiovascular diseases including atherosclerosis, myocardial infarction, stroke, and abdominal aortic aneurysm. Moreover, new insights have changed our previous notion of leukotrienes as mediators of inflammatory reactions to molecules that can fine-tune the innate and adaptive immune response. Here, we review the most recent understanding of the leukotriene cascade with emphasis on recently identified roles in immune reactions and pathophysiology.

Pharmacological characterization of the first potent and selective antagonist at the cysteinyl leukotriene 2 (CysLT(2)) receptor

BACKGROUND AND PURPOSE

Cysteinyl leukotrienes (CysLTs) have been implicated in the pathophysiology of inflammatory and cardiovascular disorders. Their actions are mediated by CysLT(1) and CysLT(2) receptors. Here we report the discovery of 3-({[(1S,3S)-3-carboxycyclohexyl]amino}carbonyl)-4-(3-{4-[4-(cyclo-hexyloxy)butoxy]phenyl}propoxy) benzoic acid (HAMI3379), the first potent and selective CysLT(2) receptor antagonist.

EXPERIMENTAL APPROACH

Pharmacological characterization of HAMI3379 was performed using stably transfected CysLT(1) and CysLT(2) receptor cell lines, and isolated, Langendorff-perfused, guinea pig hearts.

KEY RESULTS

In a CysLT(2) receptor reporter cell line, HAMI3379 antagonized leukotriene D(4)- (LTD(4)-) and leukotriene C(4)- (LTC(4)-) induced intracellular calcium mobilization with IC(50) values of 3.8 nM and 4.4 nM respectively. In contrast, HAMI3379 exhibited very low potency on a recombinant CysLT(1) receptor cell line (IC(50) > 10 000 nM). In addition, HAMI3379 did not exhibit any agonistic activity on both CysLT receptor cell lines. In binding studies using membranes from the CysLT(2) and CysLT(1) receptor cell lines, HAMI3379 inhibited [(3)H]-LTD(4) binding with IC(50) values of 38 nM and >10 000 nM respectively. In isolated Langendorff-perfused guinea pig hearts HAMI3379 concentration-dependently inhibited and reversed the LTC(4)-induced perfusion pressure increase and contractility decrease. The selective CysLT(1) receptor antagonist zafirlukast was found to be inactive in this experimental setting.

CONCLUSIONS AND IMPLICATIONS

HAMI3379 was identified as a potent and selective CysLT(2) receptor antagonist, which was devoid of CysLT receptor agonism. Using this compound, we showed that the cardiac effects of CysLTs are predominantly mediated by the CysLT(2) receptor.

Sulfido-peptide leukotrienes in coronary heart disease - relationship with disease instability and myocardial ischaemia

BACKGROUND

Urinary excretion of leukotriene (LT) E(4) is an index of LTC(4) biosynthesis and platelet-neutrophil interactions, which may occur in coronary heart disease and contribute to myocardial ischaemia. Enhanced LTC(4) biosynthesis may be a consequence of myocardial ischaemia or be linked to its pathogenetic substrate.

METHODS AND RESULTS

Overnight urine collections were obtained from 17 patients with chronic stable angina, three patients with Prinzmetal's angina, 16 patients with non ST-elevation acute coronary syndromes (NSTE-ACS) and six patients with acute ST-elevation myocardial infarction (STEMI). LTE(4) excretion was measured by enzyme immunoassay after HPLC separation. Compared with healthy controls (51.1 +/- 21.3 pg mg(-1) creatinine, mean +/- SD, n = 11) and with non-coronary cardiac controls (36.6 +/- 9.8 pg mg(-1) creatinine, n = 9), LTE(4) excretion was unchanged in stable angina (40.5 +/- 25.8 pg mg(-1) creatinine), but significantly (P < 0.01) increased in NSTE-ACS (122.7 +/- 137.2 pg mg(-1) creatinine) and STEMI (213.4 +/- 172.4 pg mg(-1) creatinine). In these patients, LTE(4) excretion rapidly dropped after day 1, consistent with effective coronary reperfusion. In patients with NSTE-ACS, the increase in LTE(4) excretion was entirely restricted to patients with recent (< 48 h) spontaneous anginal episodes. Myocardial ischaemia elicited by a positive exercise stress test was not accompanied by any detectable increase in LTE(4) excretion, while a significant (P < 0.01) increase was detected after a single-vessel percutaneous coronary interventions (PCI) procedure (n = 10), as compared with diagnostic angiography (n = 9).

CONCLUSIONS

In coronary heart disease, increased LTC(4) biosynthesis is restricted to ACS and not linked to myocardial ischaemia per se, but likely to the occurrence of plaque disruption.

The 5-lipoxygenase/leukotriene pathway in preclinical models of cardiovascular disease

Leukotrienes (LTs) derived from 5-lipoxygenase (5-LO) activity are most widely known for their actions during acute inflammation and asthma. 5-LO/LT pathway involvement in cardiovascular disease (CVD) pathogenesis has come to the forefront based on provocative human genetic/population and animal studies leading to the hypothesis that this pathway promotes atherosclerosis, abdominal aortic aneurysm, and myocardial infarction/reperfusion injury via increased leucocyte chemotaxis, vascular inflammation and enhanced permeability, and subsequent tissue/matrix degeneration. A series of pre-clinical studies have tested this hypothesis by means of genetic or pharmacological inhibition of either the LT biosynthesis axis (5-LO, 5-LO-activating protein, LTA(4) hydrolase, LTC(4) synthase) or the cognate LT receptors. Here, we summarize, compare, and analyse these animal studies and relate their findings to human disease pathogenesis. We draw a complex picture of 5-LO/LT participation in cardiovascular disorders, which is further complicated by marked differences between species. Moreover, we discuss how the cytokine footprint of the respective pathological conditions determines the expression level and hence, the contribution of components of the pathway to the overall disease state. Current knowledge implies a role for 5-LO and LTs during the early/acute phase of CVD, but our understanding of a putative 5-LO/LT involvement in more advanced stages of CVD is limited, thereby preventing simple extrapolation of findings from animal studies to humans.

Common variants of four bilirubin metabolism genes and their association with serum bilirubin and coronary artery disease in Chinese Han population

OBJECTIVES

Studies have revealed an inverse relationship between serum total bilirubin (TBIL) levels and coronary artery disease (CAD). This study investigated the genetic variants of four bilirubin metabolism genes--heme oxygenase-1 (HMOX1), biliverdin reductase A (BLVRA), solute carrier organic anion transporter family member 1B1 (SLCO1B1), and uridine diphosphate glycosyltransferase 1A1 (UGT1A1)--in relation to TBIL levels and CAD.

METHODS AND RESULTS

Thirty-five common single nucleotide polymorphisms (SNPs) were genotyped in 2380 unrelated Han participants who underwent angiocardiography at hospitals in Shanghai, China. Only three genetic variants--rs4399719 (UGT1A1 T-2473G), rs887829 (UGT1A1 G-364A), and rs4148323 (UGT1A1 G211A)--were associated with TBIL levels (each P<0.001). Four significant associations with CAD were detected after controlling age and the false discovery rate at 15%: the recessive effect of SNP rs887829 (UGT1A1 G-364A) [age-adjusted odds ratio (OR): 0.24; 95% confidence interval (CI): 0.10-0.60; P=0.0014] and dominant effect of rs4149013 (SLCO1B1 A-12099G) (age-adjusted OR: 0.70; 95% CI: 0.55-0.91; P=0.0069) on male CAD, and the additive effects of rs2877262 (BLVRA G+1238/in6C) (age-adjusted OR: 0.73; 95% CI: 0.59-0.89; P=0.0021) and rs2690381 (BLVRA G+2613/in6A) (age-adjusted OR: 0.70; 95% CI: 0.56-0.86; P=0.0008) on female CAD. SNPs rs2877262 and rs2690381 were both in a linkage disequilibrium block within BLVRA with r greater than 0.750. Correspondingly, this block was identified to be associated with female CAD.

CONCLUSION

Our study provides genetic evidences for the difference in the impact of these four bilirubin metabolism genes on TBIL levels and CAD.

Inhibition of lipoxygenases and cyclooxygenases by linoleyl hydroxamic acid: comparative in vitro studies

In this first comparative in vitro study, linoleyl hydroxamic acid (LHA), a simple and stable derivative of linoleic acid, was tested as an inhibitor of several enzymes involved in arachidonic acid metabolism in mammals. The tested enzymes were human recombinant 5-lipoxygenase (h5-LO), porcine leukocyte 12-LO, rabbit reticulocyte 15-LO, ovine cyclooxygenases 1/2 (COX1/COX2), and human microsomal prostaglandin E synthase-1 (mPGES-1). Potato tuber and soybean lipoxygenases (ptLOX and sLOX, respectively) were studied for comparative purposes. LHA inhibited most of the tested enzymes with the exception of mPGES-1. The LHA inhibitory activity increased as follows: mPGES-1 (no inhibition)<<COX1 = COX2<h5-LO = sLOX = ptLOX<12-LO<<15-LO. The IC(50) values for COX1/COX2, h5-LO, 12-LO, and 15-LO were 60, 7, 0.6, and 0.02 muM, respectively. sLOX was the only tested enzyme that was capable of aerobic oxygenation of LHA, producing 13-hydroperoxy-LHA. The enzyme rapidly inactivated during the reaction. Therefore, LHA could be used as an effective LO/LOX inhibitor without affecting COX1/COX2 and mPGES-1. Possible implications of this observation include treating diseases and pathological states that are caused by (or lead to) hyperproduction of LO-derived metabolites, e.g., inflammation, cardiovascular disorders, cancer, asthma, allergies, psoriasis, and stroke.

Increased leukotriene c4 synthesis accompanied enhanced leukotriene c4 synthase expression and activities of ischemia-reperfusion-injured liver in rats

BACKGROUND

Hepatic ischemia-reperfusion (I/R) injury is an important clinical issue and relates to cysteinyl leukotrienes (LTs), the first committed synthesis step of which is that LTC4 synthesis enzymes including leukotriene C4 synthase (LTC4S), microsomal glutathione-S-transferase (mGST)2, and mGST3-catalyzed LTA4 and reduced glutathione (GSH), to generate LTC4. However, the mechanisms of LTC4 generation during hepatic I/R are far from being elucidated.

MATERIALS AND METHODS

Adult male Sprague Dawley rats were divided into two groups: sham group (control) and I/R group. Liver was subjected to 60 min of partial hepatic ischemia followed by 5 h of reperfusion; saline was administered intravenously. LTC4 content, the activities, and expressions of LTC4 synthesis enzymes were examined with reversed phase high-performance liquid chromatography, reverse transcriptase-polymerase chain reaction, immunoblot, and immunohistochemistry, respectively. Liver damage was assessed by serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) measurements and histological observation. The superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in liver tissue were used to evaluate lipid peroxidation, and oxidative stress was estimated by the reduced GSH level in liver tissue in the pathological process.

RESULTS

Compared with control, LTC4 content, the LTC4 synthesis enzymes' activities, and the mRNA and protein expressions of LTC4S were significantly increased, while the mRNA expressions of mGST2 and mGST3 were declined obviously in rat liver during I/R (P < 0.05); most hepatocytes and sinusoidal endothelial cells expressed intensively LTC4S in an I/R-sensitive manner. This was accompanied by the increase in serum ALT and AST levels together with liver tissue MDA content (P < 0.05), the decrease in liver tissue GSH level, and SOD activity (P < 0.05), as well as histological damage. There were no differences in the protein expression of mGST3 between control and I/R groups.

CONCLUSIONS

These results demonstrated that hepatic I/R injury up-regulated the mRNA and protein expressions of LTC4S in hepatocytes and sinusoidal endothelial cells and enhanced the activities of the LTC4 synthesis enzymes. It suggests that LTC4 accumulation after hepatic I/R can be caused partially by LTC4S expression up-regulation and the LTC4 synthesis enzymes' activities augment to which LTC4S rather than mGST2 or mGST3 may mainly contribute.

Modulation of aspirin-insensitive eicosanoid biosynthesis by 6-methylprednisolone in unstable angina

BACKGROUND

The evidence that inflammation plays a pivotal role in the pathophysiology of acute coronary syndromes prompted us to investigate the effects of glucocorticoid treatment on leukotriene (LT) C4 and thromboxane (TX) A2 biosynthesis in unstable angina.

METHODS AND RESULTS

Urinary LTE4 and 11-dehydro-TXB2 were significantly higher in 12 patients with unstable angina than in 12 patients with stable angina and 12 patients with nonischemic chest pain. Furthermore, we randomized the unstable angina patients to receive intravenous 6-methylprednisolone (6-MP; 1 mg/kg BID for 2 days) or matching placebo and collected 12 consecutive 6-hour urine samples before and during the infusions. LTE4 excretion showed a time-dependent decrease in the 6-MP group but did not decrease during placebo. Furthermore, during myocardial ischemia, LTE4 was significantly higher before 6-MP infusion than during steroid therapy. In contrast, 11-dehydro-TXB2 did not differ significantly during 6-MP versus placebo. Myocardial ischemia elicited by stress test in the stable angina patients was not accompanied by any change in LTE4 and 11-dehydro-TXB2, thus ruling out a role of ischemia per se in the induction of increased eicosanoid production.

CONCLUSIONS

Increased production of vasoactive LT and TX may occur in unstable angina despite conventional antithrombotic and antianginal treatment. Glucocorticoids can suppress LTC4 biosynthesis in the short term and may provide an interesting tool to explore the pathophysiological significance of inflammatory cell activation in this setting.