Lysophosphatidic acid (LPA) has been shown to be immunomodulatory in vitro, including causing chemotaxsis, increasing T-cell and macrophage survival (1), causing platelet aggregation (2) and enhancing wound healing (3). Circulating LPA is produced by platelets and red blood cells, however, a majority of LPA is produced by catalytic action on other lipid species, especially lysophospholipase D acting on lysophosphatidylcholine. LPA binds to specific G-protein-coupled receptors belonging to the endothelial differentiation gene (Edg) subfamily, LPA1 LPA2 LPA3. Receptor activation results in signal transduction via Ras-MAP kinase, Rho/Rac, phospholipase C and inhibition of adenylyl cyclase (4). A forth membrane bound receptor not belonging to the Edg subfamily has been reported, although its biological significance has not been fully established (5). LPA is also abundant in cytoplasm and has recently been reported to be a ligand for PPAR-γ, although not PPAR-α or PPAR-δ (6, 7).
Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. PPARs regulate gene transcription by the formation of heterodimers with retinoid X receptors and binding to specific PPAR response elements. This results in activation or suppression of the target genes. Ligands for PPAR-γ have been shown to have anti-inflammatory properties both in vivo and in vitro (8, 9). Notably, ligands for PPAR-γ have previously been shown to protect against the multiple organ injury associated with endotoxemia (10, 11), administration of Gram-positive and Gram-negative cell wall fragments (12), polymicrobial sepsis (13), zymosan induced shock (14) and hemorrhagic shock (15). The role of PPAR-γ in regulating inflammatory responses and potential therapeutic approaches for PPAR-γ ligands in sepsis, inflammation and ischemia/reperfusion injury has recently been reviewed (16). As mentioned above, LPA has been reported to activate PPAR-γ. Specifically, it has been reported that (unsaturated) LPA 18:1 competes with radiolabeled PPAR-γ ligands for binding to PPAR-γ, however, (saturated) LPA 18:0 was less effective at competing for PPAR-γ (6). Also activation of PPAR-γ by various LPA species has been reported to be dependant on acyl chain saturation. Specifically, unsaturated LPA (LPA 18:1, LPA 18:2, LPA 18:3 and LPA 20:4) significantly activated PPAR-γ, however saturated LPA (LPA 16:0, LPA 18:0 and LPA 20:0) did not activate PPAR-γ (7). The specific PPAR-γ antagonist GW9662 has also been shown to attenuate PPAR-γ activation by unsaturated LPA both in vitro and in vivo (7).
Interestingly, LPA has been shown to be protective in animal models of inflammation, including renal ischemia-reperfusion (17), wound healing (18) and colitis (19), and there is evidence that ligands of PPAR-γ are also beneficial in these conditions (20). Thus, LPA may provide a novel therapeutic opportunity for reducing the multiple organ injury associated with endotoxemia as i) LPA has been previously shown to be protective in animal models of inflammation (17-19) and ii) saturated species of LPA are ligands for PPAR-γ (6, 7) and that other ligands for PPAR-γ have previously been shown to be beneficial in animal models of inflammation (10, 12-14).
Hence, this study was undertaken to investigate the effects of both (saturated) LPA 18:0 and (unsaturated) LPA 18:1 (Fig. 1 on i) the hemodynamic alterations, ii) the liver injury, iii) the neuromuscular injury and iv) the alterations in plasma IL-1β and IL-6 levels caused by severe acute endotoxemia in the rat. We have also investigated whether activation of LPA of either i) LPA G-protein-coupled receptors or ii) PPAR-γ mediates any of the observed effects using the specific antagonists Ki16425 and GW9662 (2-choloro-nitrobenzanilide), respectively.
MATERIALS AND METHODS
Surgical procedure and quantification of organ injury/dysfunction
This study was carried out on 118 male Wistar rats (Charles River, Kent, UK) weighing 230-320g, receiving a standard diet and water ad libitum. The investigation was performed in accordance with the Home Office Guidance on the Operation of the Animals (Scientific Procedures) Act 1986, published by HMSO, London. All animals were anaesthetized with thiopentone sodium (Intraval®, 120 mg/kg, i.p.), and anesthesia was maintained by supplementary injections of thiopentone sodium (approximately 1-2 mg/kg/h i.v.) as required. The general surgical procedures were performed as previously described (21). Briefly, a tracheostomy was performed to maintain airway patency and facilitate spontaneous breathing and polyethylene catheters were positioned in the carotid artery, for mean arterial pressure (MAP) and heart rate (HR) monitoring, jugular vein, for administration of drugs, vehicles and/or saline, and bladder to prevent post renal failure. Upon completion of the surgical procedure, MAP and HR were allowed to stabilize for 20 min. 6 h after administration of LPS, 1.5 ml of blood was collected from the carotid into a serum gel S/1.3 tube (Sarstedt, Germany) from a catheter placed in the carotid artery, and plasma values for indices of liver (22) and neuromuscular injury (23) were examined as previously described.
A dose of 1 mg/kg LPA has been previously shown to prevent renal ischemia-reperfusion injury and was therefore included in this study. GW9662 has previously been reported to antagonize PPAR-γ in the nanomolar range (24) and doses of 0.3-1 mg/kg have been shown reduce organ protection afforded by PPAR-γ ligands in this animal model (10). Thus, a dose of 1 mg/kg was used in this study. Animals were assigned to 15 different groups (Table 1):
- Sham Control. Rats received vehicle for LPS (1 ml/kg saline i.v.), 10% DMSO (vehicle for Ki16425 and GW9662, 1 ml/kg i.v.) and 2% BSA in PBS (vehicle for LPA, 1 ml/kg i.v., n = 11).
- Sham 18:0. Rats received vehicle for LPS (1 ml/kg saline i.v.), 10% DMSO (vehicle for Ki16425 and GW9662, 1 ml/kg i.v.) and were treated with LPA 18:0 (1 mg/kg i.v., n = 7).
- Sham 18:1. Rats received vehicle for LPS (1 ml/kg saline i.v.), 10% DMSO (vehicle for Ki16425 and GW9662, 1 ml/kg i.v.) and were treated with LPA 18:1 (1 mg/kg i.v., n = 5).
- Sham Ki16425. Rats received vehicle for LPS (1 ml/kg saline i.v.) and 2% BSA in PBS (vehicle for LPA, 1 ml/kg i.v.) and were treated with Ki16425 (0.5 mg/kg i.v., n-5).
- Sham GW9662. Rats received vehicle for LPS (1 ml/kg saline i.v.) and 2% BSA in PBS (vehicle for LPA, 1 ml/kg i.v.) and were treated with GW9662 (1 mg/kg i.v., n = 4).
- LPS Control. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received the vehicle for vehicle for Ki16425 and GW9662 (1 ml/kg i.v. 10 % DMSO) and 1 h after LPS received vehicle for LPA (1 ml/kg i.v. 2% BSA in PBS, n = 12).
- LPS + Ki16425. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later were treated with Ki16425 (0.5 mg/kg i.v.) and 1 h after LPS received vehicle for LPA (1 ml/kg i.v. 2% BSA in PBS, n = 5).
- LPS + GW9662. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later were treated with GW9662 (1 mg/kg i.v.) and 1 h after LPS received vehicle for LPA (1 ml/kg i.v. 2% BSA in PBS, n = 7).
- LPS + 18:0. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received the vehicle for vehicle for Ki16425 and GW9662 (1 ml/kg i.v. 10 % DMSO) and 1 h after LPS received LPA 18:0 (1 mg/kg i.v., n = 9).
- LPS + Ki16425 + 18:0. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received Ki16425 (0.5 mg/kg i.v.) and 1 h after LPS received LPA 18:0 (1 mg/kg i.v., n = 8).
- LPS + GW9662 + 18:0. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received GW9662 (1 mg/kg i.v.) and 1 h after LPS received LPA 18:0 (1 mg/kg i.v., n = 9).
- LPS + 18:1. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received the vehicle for vehicle for Ki16425 and GW9662 (1 ml/kg i.v. 10 % DMSO) and 1 h after LPS received LPA 18:1 (1 mg/kg i.v., m = 9).
- LPS + Ki16425 + 18:1. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received Ki16425 (0.5 mg/kg i.v.) and 1 h after LPS received LPA 18:1 (1 mg/kg i.v., n = 9).
- LPS + GW9662 + 18:1. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later received GW9662 (1 mg/kg i.v.) and 1 h after LPS received LPA 18:1 (1 mg/kg i.v., n = 9).
- LPS + Ki16425 + GW9662 + 18:1. Rats received LPS (6 mg/kg i.v. over 10 min), 30 min later were co-administered with Ki16425 (0.5 mg/kg i.v.) and GW9662 (1 mg/kg i.v.) and 1 h after LPS received LPA 18:1 (1 mg/kg i.v., n = 9).
Plasma IL-1β measurements
Carotid blood was taken 6 h after LPS administration and centrifuged at 10,000 RPM. Plasma samples were frozen and stored at −80°C until analyzed as previously described (25). Following the manufactures protocol, sandwich ELISAs from R&D Systems (Minneapolis, USA) were performed to determine the plasma levels of IL-1β and IL-16. Samples were analyzed using a microplate reader set to 450 nm and corrected at a wavelength of 540 nm. All samples were analyzed in duplicate.
LPA suspensions were prepared in PBS containing 2% BSA and ultra-sonnicated for 15 seconds. Ki16425 and all other materials were purchased from Sigma-Aldrich Company Ltd. (Poole, UK), unless otherwise stated. LPA 18:0 (1-stearoyl-2-hydroxy-sn-glycero-3-phosphate) and LPA 18:1 (1-Oleoyl-2-Hydroxy-sn-Glycero-3-Phosphate) were purchased from Avanti Polar Lipids (Alabaster, Alabama, USA). GW9662 was purchased from Axxora (UK) Ltd (Nottingham, UK). Thiopentone sodium (Intraval Sodium®) was purchased from Rhône Mérieux Ltd. (Harlow, UK). Non-pyrogenic saline (0.9% NaCl) was acquired from Baxter Healthcare Ltd. (Thetford, UK). PBS was attained from Invitrogen (Paisley, UK).
All data are presented as means ± SEM of n observations, where n represents the number of animals or blood samples studied. For repeated hemodynamic measurements a two-way analysis of variance (ANOVA) was performed followed by a Bonferroni post test. Data without repeated measurements (multiple organ injury and cytokines analysis) was analyzed by one-way ANOVA, followed by a Bonferroni post hoc test for multiple comparisons. A P value of less than 0.05 was considered statistically significant.
Effects of LPA on the circulatory failure associated with endotoxemia
Prior to LPS administration, mean baseline values for MAP (Table 2) and HR (data not shown) were similar in all experimental groups. Values ranged from 116 ± 4 to 132 ± 4 mm Hg and 397 ± 7 to 443 ± 8 beats per minute (bpm), respectively. Compared to Sham Controls, animals administered with either Ki16425, GW9662, LPA 18:0 or LPA 18:1 alone exhibited similar hemodynamics (P > 0.05).
When compared to Sham-operated rats, administration of LPS (6 mg/kg) resulted in a significant, biphasic fall in MAP from 132 ± 4 (baseline) to 85 ± 3 mm Hg at 6 h after injection of LPS. Administration of either LPA 18:0 or LPA 18:1 did not affect the fall in MAP caused by endotoxin at any time point (P > 0.05).
When compared to Sham-operated animals, endotoxemia for 6 h resulted in a significant increase in HR from 401 ± 10 (baseline) to 482 ± 10 beats per min (data not shown). This tachycardia was not affected by either LPA 18:0 or LPA 18:1 (P > 0.05). Administration of Ki16425 or GW9662 without LPA had no effect on the biphasic fall in MAP or tachycardia resulting from endotoxemia in any experimental group (P > 0.05).
Effects of LPA on the organ injury caused by endotoxemia
When compared to Sham-operated controls, endotoxemia for 6 h resulted in significant increases in serum levels of aspartate aminotransferase (AST, Fig. 2) and alanine aminotransferase (ALT, Fig. 3), both markers of liver injury, and creatine kinase (CK, Fig. 4), a marker of neuromuscular injury (P < 0.05).
When compared to LPS controls, treatment of animals with LPA 18:0 1 h after LPS administration caused a significant reduction in the serum levels of AST (Fig. 2A), ALT (Fig. 3A) and CK (Fig. 4A) (P < 0.05). When compared to animals administered with LPS and treated with LPA 18:0, infusion of the specific LPA receptor antagonist Ki16425 significantly attenuated the organ protection provided by LPA 18:0 (P < 0.05). However, administration of the specific PPAR-γ receptor antagonist, GW9662, had no effect on the organ protection afforded by LPA 18:0.
Interestingly, when compared to LPS controls, treatment of animals with LPA 18:1 1 h after LPS administration caused a significant reduction in the serum levels of AST (Fig. 2B), ALT (Fig. 3B) and CK (Fig. 4B) (P < 0.05). However, when animals were infused with either the specific LPA receptor antagonist, Ki16425, or the specific PPAR-γ receptor antagonist, GW9662, this protective effect was reduced. Furthermore, when compared to animals receiving LPS and LPA 18:1 alone, co-administration with both Ki16425 and GW9662 significantly attenuated the organ protective effects of LPA 18:1 (P < 0.05).
When compared to Sham-operated controls, animals receiving either Ki16425, GW9662 or LPA18:0 or LPA 18:1 without causing endotoxemia, showed similar serum levels of the AST, ALT and CK (data not shown, P > 0.05). Animals receiving LPS and receptor antagonists without LPA showed similar organ injury to LPS controls (Table 3, P > 0.05).
Effects of LPA 18:0 on the increased circulating levels of IL-1β and IL-6 associated with endotoxemia
Endotoxemia resulted in a significant rise in circulating IL-1β and IL-6 levels 6 h after LPS administration when compared to Sham Control animals (Fig. 5, P < 0.05). When compared to LPS controls, administration of LPA 18:0 significantly reduced plasma IL-1β levels (Fig. 5A, P < 0.05). Serum from endotoxemic animals receiving both LPA 18:0 and Ki16425 showed attenuation of LPA 18:0 induced IL-1β reduction, which were not significantly different from animals receiving LPS alone (P > 0.05). Inhibition of PPAR-γ by GW9662 did not attenuate the reduction in circulating levels of IL-1β afforded by LPA 18:0. When compared to animals receiving LPS alone, LPA 18:0 reduced circulating levels of IL-6, although this was not significant (Fig. 5B, P > 0.05).
We demonstrate here that acute severe endotoxemia resulted in liver injury, as measured by serum AST and ALT levels, and neuromuscular injury, as measured by serum CK levels. Furthermore, endotoxemia resulted in circulatory failure (hypotension and tachycardia) and increased circulating levels of IL-1β and IL-6.
Previously LPA has been reported to be protective in animal models of renal ischemia-reperfusion (17), wound healing (18) and colitis (19). Here we demonstrate for the first time that administration of either saturated (18:0) or unsaturated (18:1) LPA significantly attenuated the liver and neuromuscular injury caused by acute severe endotoxemia in the rat. Notably, this protective effect was observed when administration of LPA occurred 1 h after administration of LPS. It has been suggested that many therapeutic approaches for septic shock have failed in clinical trials due to the utilization of prophylactic treatment regimes in experimental settings, rather than therapeutic administration (after the onset of shock and inflammation). Thus our findings, that LPA given after the induction of endotoxemia protects the liver and neuromuscular tissue against the associated injury, interestingly suggests a broader window for the therapeutic use of LPA against the systemic inflammatory response.
LPA has been reported to activate both specific G-protein-coupled receptors and PPAR-γ (6, 7). Importantly, the activation of PPAR-γ has been shown to be dependent on the saturation of the acyl chain. Specifically, it was reported that the (unsaturated) LPA 18:1 competes with radiolabeled PPAR-γ ligands (rosiglitazone and azelaic phosphatidylcholine) for binding to PPAR-γ, however, (saturated) LPA 18:0 was less effective at competing for PPAR-γ (6). Zhang and colleagues have shown that activation of PPAR-γ by various LPA species was dependant on acyl chain saturation, with unsaturated LPA (LPA 18:1, LPA 18:2, LPA 18:3 and LPA 20:4) significantly activating PPAR-γ and saturated LPA (LPA 16:0, LPA 18:0 and LPA 20:0) showing no PPAR-γ dependent effect (7). Previously, we and others have shown ligands for PPAR-γ to be protective in animal models of endotoxemia (10, 11), systemic inflammation caused by Gram-positive and Gram-negative bacterial cell wall components (12), polymicrobial sepsis (13), zymosan induced shock (14) and hemorrhagic shock (15). Thus, using specific receptor antagonists for LPA G-protein-coupled receptors (LPA1-3, Ki16425) and PPAR-γ (GW9662), we investigated the possible role of these receptors in the organ protection afforded by both LPA 18:0 and LPA 18:1.
We found that the organ protection (liver and neuromuscular) provided by LPA 18:0 was associated with LPA G-protein-coupled receptor but not PPAR-γ activation. Conversely, the organ protection provided by LPA 18:1 was associated with both G-protein-coupled receptor activation and, importantly, PPAR-γ activation. In animals receiving both LPS and LPA 18:1, co-administration of Ki16425 and GW9662 resulted in a significant attenuation of the protection afforded by LPA 18:1. Thus, LPA 18:1 reduces organ injury associated with endotoxemia by activating two distinct pathways. Interestingly, Ki16425 and GW9662 did not increase the injury in animals subjected to LPS alone, indicating that endogenous LPA provides no protection in this model of acute severe endotoxemia. We have previously shown that endogenous ligands for PPAR-γ are protective in a model of hemorrhagic shock but not in this model of endotoxemia (10, 15).
Interestingly, the fall in blood pressure caused by LPS was not prevented by either saturated or unsaturated LPA. This is not entirely surprising, as many agents which do not affect the fall in blood pressure in these models do reduce organ injury (26), while others which do attenuate the fall in blood pressure may not (27). Thus, there is no strict correlation between hemodynamic effects and outcome in this model. Furthermore, we have recently reported that the co-administration of LPS and PepG, which does not cause a fall in MAP, does cause a significant degree of organ injury/dysfunction as well as systemic inflammation (28). Also, there is clinical evidence that an improvement in blood pressure alone does not necessarily prevent organ dysfunction and injury. For instance, Le Doux and colleagues have shown that increasing MAP from 65 to 85 mm Hg with norepinephrine does not significantly affect systemic oxygen metabolism, skin microcirculatory blood flow, urine output or splanchnic perfusion in patients with septic shock (29). Thus, we believe that the observed beneficial effects of LPA are not due to a hemodynamic effect.
What then are the possible mechanism(s) by which LPA attenuates the inflammatory response and as a result protects the organs against injury? We have shown that the rise in plasma levels of IL-1β associated with endotoxemia is attenuated with LPA 18:0, indicating a possible anti-inflammatory role for LPA 18:0 in endotoxemia. This beneficial effect was blocked by Ki16425, indicating that LPA 18:0 either directly or indirectly (by reducing tissue injury or other pathways prior to IL-1β activation) attenuates the pro-inflammatory response. We have also shown that LPA 18.0 attenuates the rise in circulating levels of IL-6 associated with endotoxemia, although this was not significant. Also, previous investigation into renal ischemia-reperfusion injury has reported that LPA reduces renal apoptosis as well as release of TNF-α, neutrophil influx and complement activation (17), thus providing further possible protective mechanisms.
Limitations of the Study: Despite these findings, the identity/identities of the LPA receptors activated by LPA in this model remains elusive due to the non-selectivity of current antagonists, with Ki16425 antagonizing all LPA G-protein-coupled receptors (30). LPA1 and LPA2 have been shown to be involved in T cell proliferation and migration, respectively, and both receptors protect against T cell and macrophage apoptosis (31). The role of a putative nuclear LPA receptor showing immunomodulatory functions also remains to be established (32). Obviously, further investigation of the anti-inflammatory mechanism(s) of LPA is warranted, including the receptor subsets involved. Additionally, in this model of endotoxemia we have not provided direct evidence of PPAR-γ activation by unsaturated LPA. However, we and others have previously shown that i) ligands for PPAR-γ are protective in models of systemic inflammation (10-13, 15), ii) GW9662 has been shown to specifically antagonize PPAR-γ activation both in vitro and in vivo (7, 10, 15, 24) and iii) unsaturated LPA has previously been shown to activate PPAR-γ both in vitro and in vivo (6, 7).
In conclusion, our results show for the first time that both saturated and unsaturated LPA, given in a therapeutic regime, protects against endotoxin induced organ injury and the rise in circulating IL-1β levels. Mechanistically, this protection is dependant on acyl chain saturation, with saturated LPA activating only specific G-protein-coupled receptors but unsaturated LPA activates both G-protein-coupled receptors and PPAR-γ. We propose that LPA may be a useful strategy in the therapy of organ injury in diseases associated with shock of various aetiologies.
OM was funded by the Medical Research Council. MC was financially supported by the Helsingin Sanomat Centennial Foundation.
1. Graler MH, Goetzl EJ: Lysophospholipids and their G protein-coupled receptors in inflammation and immunity. Biochim Biophys Acta
2. Gueguen G, Gaige B, Grevy JM, Rogalle P, Bellan J, Wilson M, Klaebe A, Pont F, Simon MF, Chap H: Structure-activity analysis of the effects of lysophosphatidic acid on platelet aggregation. Biochemistry
3. Balazs L, Okolicany J, Ferrebee M, Tolley B, Tigyi G: Topical application of the phospholipid growth factor lysophosphatidic acid promotes wound healing in vivo. Am J Physiol Regul Integr Comp Physiol
4. Moolenaar WH, van Meeteren LA, Giepmans BN: The ins and outs of lysophosphatidic acid signaling. Bioessays
5. Noguchi K, Ishii S, Shimizu T: Identification of P2y9/GPR23 as a novel G protein-coupled receptor for lysophosphatidic acid, structurally distant from the edg family. J Biol Chem
6. McIntyre TM, Pontsler AV, Silva AR, St Hilaire A, Xu Y, Hinshaw JC, Zimmerman GA, Hama K, Aoki J, Arai H, et al.: Identification of an intracellular receptor for lysophosphatidic acid (LPA): LPA is a transcellular PPARgamma agonist. Proc Natl Acad Sci U S A
7. Zhang C, Baker DL, Yasuda S, Makarova N, Balazs L, Johnson LR, Marathe GK, McIntyre TM, Xu Y, Prestwich GD, et al.: Lysophosphatidic acid induces neointima formation through PPARgamma activation. J Exp Med
8. Jiang C, Ting AT, Seed B: PPAR-Gamma agonists inhibit production of monocyte inflammatory cytokines. Nature
9. Asada K, Sasaki S, Suda T, Chida K, Nakamura H: Antiinflammatory roles of peroxisome proliferator-activated receptor gamma in human alveolar macrophages. Am J Respir Crit Care Med
10. Collin M, Patel NS, Dugo L, Thiemermann C: Role of peroxisome proliferator-activated receptor-gamma in the protection afforded by 15-deoxydelta12,14 prostaglandin J2 against the multiple organ failure caused by endotoxin. Crit Care Med
11. Kaplan JM, Cook JA, Hake PW, O'Connor M, Burroughs TJ, Zingarelli B: 15-Deoxy-Delta(12,14)-Prostaglandin J(2) (15D-PGJ(2)), a peroxisome proliferator activated receptor gamma ligand, reduces tissue leukosequestration and mortality in endotoxic shock. Shock
12. Dugo L, Collin M, Cuzzocrea S, Thiemermann C: 15d-Prostaglandin J2 reduces multiple organ failure caused by wall-fragment of gram-positive and gram-negative bacteria. Eur J Pharmacol
13. Zingarelli B, Sheehan M, Hake PW, O'Connor M, Denenberg A, Cook JA: Peroxisome proliferator activator receptor-gamma ligands, 15-Deoxy-Delta (12, 14)-Prostaglandin J2 and ciglitazone, reduce systemic inflammation in polymicrobial sepsis
by modulation of signal transduction pathways. J Immunol
14. Cuzzocrea S, Pisano B, Dugo L, Ianaro A, Patel NS, Di Paola R, Genovese T, Chatterjee PK, Fulia F, Cuzzocrea E, et al.: Rosiglitazone, a ligand of the peroxisome proliferator-activated receptor-gamma, reduces the development of nonseptic shock induced by zymosan in mice. Crit Care Med
15. Abdelrahman M, Collin M, Thiemermann C: The peroxisome proliferator-activated receptor-gamma ligand 15-deoxydelta12,14 prostaglandin J2 reduces the organ injury in hemorrhagic shock. Shock
16. Zingarelli B, Cook JA: Peroxisome proliferator-activated receptor-gamma is a new therapeutic target in sepsis
and inflammation. Shock
17. de Vries B, Matthijsen RA, van Bijnen AA, Wolfs TG, Buurman WA: Lysophosphatidic acid prevents renal ischemia-reperfusion injury by inhibition of apoptosis and complement activation. Am J Pathol
18. Demoyer JS, Skalak TC, Durieux ME: Lysophosphatidic acid enhances healing of acute cutaneous wounds in the mouse. Wound Repair Regen
19. Sturm A, Zeeh J, Sudermann T, Rath H, Gerken G, Dignass AU: Lisofylline and lysophospholipids ameliorate experimental colitis in rats. Digestion
20. Sivarajah A, Chatterjee PK, Patel NS, Todorovic Z, Hattori Y, Brown PA, Stewart KN, Mota-Filipe H, Cuzzocrea S, Thiemermann C: Agonists of peroxisome-proliferator activated receptor-gamma reduce renal ischemia/reperfusion injury. Am J Nephrol
21. Millar CG, Thiemermann C: Carboxy-PTIO, a scavenger of nitric oxide, selectively inhibits the increase in medullary perfusion and improves renal function in endotoxemia. Shock
22. Hewett JA, Jean PA, Kunkel SL, Roth RA: Relationship between tumor necrosis factor-alpha and neutrophils in endotoxin-induced liver injury. Am J Physiol
23. Ruetten H, Southan GJ, Abate A, Thiemermann C: Attenuation of endotoxin-induced multiple organ dysfunction by 1-amino-2-hydroxy-guanidine, a potent inhibitor of inducible nitric oxide synthase. Br J Pharmacol
24. Leesnitzer LM, Parks DJ, Bledsoe RK, Cobb JE, Collins JL, Consler TG, Davis RG, Hull-Ryde EA, Lenhard JM, Patel L, et al.: Functional consequences of cysteine modification in the ligand binding sites of peroxisome proliferator activated receptors by GW9662
25. Dugo L, Abdelrahman M, Murch O, Mazzon E, Cuzzocrea S, Thiemermann C: Glycogen synthase kinase-3beta inhibitors protect against the organ injury and dysfunction caused by hemorrhage and resuscitation. Shock
26. Collin M, Anuar FB, Murch O, Bhatia M, Moore PK, Thiemermann C: Inhibition of endogenous hydrogen sulfide formation reduces the organ injury caused by endotoxemia. Br J Pharmacol
27. Wray GM, Millar CG, Hinds CJ, Thiemermann C: Selective inhibition of the activity of inducible nitric oxide synthase prevents the circulatory failure, but not the organ injury/dysfunction, caused by endotoxin. Shock
28. Dugo L, Collin M, Allen DA, Patel NS, Bauer I, Mervaala EM, Louhelainen M, Foster SJ, Yaqoob MM, Thiemermann C: GSK-3beta Inhibitors Attenuate the Organ Injury/Dysfunction Caused by Endotoxemia in the Rat. Crit Care Med
29. LeDoux D, Astiz ME, Carpati CM, Rackow EC: Effects of perfusion pressure on tissue perfusion in septic shock. Crit Care Med
30. Ohta H, Sato K, Murata N, Damirin A, Malchinkhuu E, Kon J, Kimura T, Tobo M, Yamazaki Y, Watanabe T, et al.: Ki16425
, a Subtype-selective antagonist for EDG-family lysophosphatidic acid receptors. Mol Pharmacol
31. Huang MC, Graeler M, Shankar G, Spencer J, Goetzl EJ: Lysophospholipid mediators of immunity and neoplasia. Biochim Biophys Acta
32. Gobeil F Jr, Bernier SG, Vazquez-Tello A, Brault S, Beauchamp MH, Quiniou C, Marrache AM, Checchin D, Sennlaub F, Hou X, Nader M, Bkaily G, Ribeiro-da-Silva A, Goetzl EJ, Chemtob S: Modulation of pro-inflammatory gene expression by nuclear lysophosphatidic acid receptor type-1. J Biol Chem