Protective Effect Of Sitagliptin Research Articles

Protective Effects of Sitagliptin on Streptozotocin-Induced Hepatic Injury in Diabetic Rats: A Possible Mechanisms.

Diabetes is a ubiquitous disease that causes several complications. It is associated with insulin resistance, which affects the metabolism of proteins, carbohydrates, and fats and triggers liver diseases such as fatty liver disease, steatohepatitis, fibrosis, and cirrhosis. Despite the effectiveness of Sitagliptin (ST) as an antidiabetic drug, its role in diabetes-induced liver injury is yet to be fully investigated. Therefore, this study aims to investigate the effect of ST on hepatic oxidative injury, inflammation, apoptosis, and the mTOR/NF-κB/NLRP3 signaling pathway in streptozotocin (STZ)-induced liver injury. Rats were allocated into four groups: two nondiabetic groups, control rats and ST rats (100 mg/kg), and two diabetic groups induced by STZ, and they received either normal saline or ST for 90 days. Diabetic rats showed significant hyperglycemia, hyperlipidemia, and elevation in liver enzymes. After STZ induction, the results revealed remarkable increases in hepatic oxidative stress, inflammation, and hepatocyte degeneration. In addition, STZ upregulated the immunoreactivity of NF-κB/p65, NLRP3, and mTOR but downregulated IKB-α in liver tissue. The use of ST mitigated metabolic and hepatic changes induced by STZ; it also reduced oxidative stress, inflammation, and hepatocyte degeneration. The normal expression of NF-κB/p65, NLRP3, mTOR, and IKB-α were restored with ST treatment. Based on that, our study revealed for the first time the hepatoprotective effect of ST that is mediated by controlling inflammation, oxidative stress, and mTOR/NF-κB/NLRP3 signaling.

Sitagliptin mitigates hypoxia/reoxygenation (H/R)-induced injury in cardiomyocytes by mediating sirtuin 3 (SIRT3) and autophagy

ABSTRACT Potential ischemia/reperfusion (I/R) injuries are commonly induced during treatment of cardiovascular diseases, such as acute myocardial infarction (AMI). It is reported that oxidative stress and over-autophagy in cardiomyocytes are involved in the pathogenesis of I/R injury. Sitagliptin is an effective inhibitor of dipeptidyl peptidase 4 (DPP-4) for the treatment of diabetes, which is recently reported to regulate oxidative stress and autophagy. The present study is designed to explore the function of Sitagliptin on I/R injury. Hypoxia/reoxygenation (H/R) condition was used to simulate the I/R injury on cardiomyocytes. We found that the declined cell viability and elevated expression level of creatine kinase myocardial band (CK-MB) were observed in the H/R group, accompanied by the increased mitochondrial reactive oxygen species (ROS), elevated cellular malondialdehyde (MDA) level, and mitochondrial dysfunction. After Sitagliptin treatment, the damages in H9c2 cardiomyocytes, oxidative stress, and mitochondrial dysfunction were significantly alleviated. In addition, the overactivated autophagy and mitophagy in H/R-challenged cardiomyocytes were dramatically mitigated by Sitagliptin, accompanied by the upregulation of SIRT3. Lastly, the protective effect of Sitagliptin on H/R-induced mitophagy, autophagy, and damages in cardiomyocytes was dramatically abolished by the knockdown of SIRT3. Taken together, our data reveal that Sitagliptin ameliorated the H/R-induced injury in cardiomyocytes by mediating sirtuin 3 (SIRT3) and autophagy.

The Effect of Sitagliptin on Inflammatory Mediators in the Ovary of Rat with Polycystic Ovary Syndrome

Background and Aims: Polycystic ovary syndrome (PCOS) is an endocrine and metabolic disease in females of reproductive age and is a significant infertility cause. Inflammation plays a crucial role in the pathogenesis of PCOS. The present study evaluated whether sitagliptin, dipeptidyl peptidase-4 inhibitor, attenuates inflammatory markers C-reactive protein (CRP), interleukin(IL)-6, tumor necrosis factor-α (TNF-α), IL-1β, and transforming growth factor-β (TGF-β) in a rat model of PCOS.
 Materials and Methods: Twenty-two female adult Wistar rats were randomly divided into four groups: control, PCOS model, PCOS+sitagliptin (25 mg/kg), and PCOS+sitagliptin (50 mg/kg). PCOS was induced by injection of estradiol valerate, intraperitoneally. Sitagliptin was gavaged daily for 30 days to both groups of animals. After the treatment period, blood and ovaries tissue were collected to analyze inflammatory parameters.
 Results: The mRNA levels of IL-6, IL-1β, TGF-β, and TNF-α in the PCOS model group were markedly elevated compared with the control group (p<0.01). These parameters' mRNA levels were reduced in the sitagliptin treatment groups compared with the PCOS group (p<0.01). Also, the serum concentration of CRP in the PCOS group was more than the control. This increase significantly decreased in groups treated with sitagliptin compared with the PCOS group.
 Conclusion: The presented study suggested that the protective effects of sitagliptin on PCOS may be due to its inhibitory effect on expression and inflammatory markers' levels.

Sitagliptin attenuates endothelial dysfunction independent of its blood glucose controlling effect

Although the contributions of sitagliptin to endothelial dysfunction in diabetes mellitus were previously reported, the mechanisms still undefined. Autophagy plays an important role in the development of diabetes mellitus, but its role in diabetic macrovascular complications is unclear. This study aims to observe the effect of sitagliptin on macrovascular endothelium in diabetes and explore the role of autophagy in this process. Diabetic rats were induced through administration of high-fat diet and intraperitoneal injection of streptozotocin. Then diabetic rats were treated with or without sitagliptin for 12 weeks. Endothelial damage and autophagy were measured. Human umbilical vein endothelial cells were cultured either in normal glucose or in high glucose medium and intervened with different concentrations of sitagliptin. Rapamycin was used to induce autophagy. Cell viability, apoptosis and autophagy were detected. The expressions of proteins in c-Jun N-terminal kinase (JNK)-Bcl-2-Beclin-1 pathway were measured. Sitagliptin attenuated injuries of endothelium in vivo and in vitro. The expression of microtubuleassociated protein 1 light chain 3 II (LC3II) and beclin-1 were increased in aortas of diabetic rats and cells cultured with high-glucose, while sitagliptin inhibited the over-expression of LC3II and beclin-1. In vitro pre-treatment with sitagliptin decreased rapamycin-induced autophagy. However, after pretreatment with rapamycin, the protective effect of sitagliptin on endothelial cells was abolished. Further studies revealed sitagliptin increased the expression of Bcl-2, while inhibited the expression of JNK in vivo. Sitagliptin attenuates injuries of vascular endothelial cells caused by high glucose through inhibiting over-activated autophagy. JNK-Bcl-2-Beclin-1 pathway may be involved in this process.

Protective effect of sitagliptin and whole-body γ-irradiation in diabetes-induced cardiac injury.

Diabetes mellitus is associated with an increased risk of cardiac complications; this study aimed to investigate effect of sitagliptin (SITA) alone or combined with γ-irradiation on diabetes-associated cardiac injury. Rats were treated with SITA (100mg/kg per day; p.o.) for 2weeks followed by a single dose of whole-body γ-irradiation (3Gy). Solitary administration of SITA or combined treatment with γ-irradiation succeeded to ameliorate the increase in serum levels of glucose, total cholesterol, triglycerides, creatine kinase-MB, and malondialdehyde, coupled by increased insulin and reduced glutathione levels. Their cardioprotective potential was confirmed through attenuating the apoptotic signaling by mitigating Bcl-2-associated X protein, caspase-3, and apoptosis-inducing factor expression, while augmenting the anti-apoptotic factors, B cell lymphoma-2 (Bcl-2), and heat shock protein 70 (HSP-70) in left ventricular tissue homogenates. These findings were supported histopathologically. In conclusion, treatment with SITA alone or combined with γ-irradiation may prove beneficial in diabetes-accompanied cardiac insult. This could be due to the crosstalk between the antioxidant, anti-apoptotic, and restoration of body's defense capacities.

Sitagliptin-Dependent Differences in the Intensity of Oxidative Stress in Rat Livers Subjected to Ischemia and Reperfusion.

Purpose Ischemia/reperfusion (IR) is the main cause of liver damage after transplantation. We evaluated the effect of sitagliptin (STG) on oxidative stress parameters in the rat liver under IR. Methods Rats were treated with STG (5 mg/kg) (S and SIR) or saline solution (C and CIR). Livers from CIR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). During reperfusion, aminotransferases (ALT and AST) were determined in blood samples. Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), paraoxonase-1 (PON1), glutathione peroxidase (GPx), and the mRNA expression of SOD1 were determined in liver homogenates after reperfusion. Different regions of livers were also histologically evaluated. Results The PON1 activity was higher, and the TBARS level was lower in SIR than in CIR. There was an inverse relationship between TBARS and PON1 levels in the whole cohort. The GPx activity was lower in ischemic than in nonischemic groups regardless of the STG treatment. In SIR, the SOD1 activity was higher compared to that in CIR. In S, the expression of SOD1 mRNA was the highest of all examined groups and positively correlated with the SOD1 activity in the whole animal cohort. During IR aminotransferases, the activity in the drug-treated group was lower in all examined points of time. In drug-treated groups, the percentage of steatosis was higher than that in nontreated groups regardless of IR. Conclusions The protective effect of STG on the rat liver, especially its antioxidant properties, was revealed under IR conditions.

Sitagliptin prevents isoproterenol-induced myocardial infarction in rats by modulating nitric oxide synthase enzymes

Ischemic heart disease is a common cause of mortality worldwide. Sitagliptin is a new anti-diabetic drug acting as dipeptidyl peptidase-4 (DPP-4) inhibitor. The study investigated the ability of sitagliptin to prevent pathological changes of isoproterenol- (ISO-) induced myocardial injury in rats. The role of nitric oxide (NO) was also reported. Rats were assorted into six groups (n = 7) and treated for 12 days. Group 1: normal control, received normal saline. Group 2, sitagliptin control, received sitagliptin (10 mg/kg, orally). Group 3, ISO group, received isoproterenol (ISO) (100 mg/kg, i.p.). Group 4, sitagliptin + ISO, co-treated with sitagliptin plus ISO. Group 5, L-NNA + ISO, co-treated with L-NG-nitro arginine (L-NNA) (25 mg/kg, orally) plus ISO. Group 6, sitagliptin + L-NNA + ISO, co-treated with sitagliptin plus ISO plus L-NNA. Blood glucose, serum creatine kinase-MB (CK-MB, and cardiac tissue parameters of oxidative stress parameters and NO, along with histopathological examination, and immunohistochemical study of inducible NO synthase (iNOS) expression were done. The results showed that sitagliptin caused a significant reduction in CK-MB, and attenuated histopathological damage-induced by ISO. Its effect was associated with a significant decrease in oxidative stress parameters, NO contents as well as by a significant decrease in the expression of iNOS in cardiac tissue. The protective effect of sitagliptin was abrogated by coadministartion of L-NNA, a selective inhibitor of both endothelial NOS (eNOS) and neuronal NOS (nNOS). In conclusion, sitagliptin ameliorates ISO-induced myocardial injury via antioxidant effects and modulation of NOS enzymes.

Influence of Dipeptidyl Peptidase-IV Inhibitor Sitagliptin on Extracellular Signal-Regulated Kinases 1/2 Signaling in Rats with Diabetic Nephropathy

The protective effects of sitagliptin on the kidneys of rats with diabetic nephropathy (DN) and its influence on extracellular signal-regulated kinases 1/2 (ERK1/2) signaling were investigated. Male Wistar rats (n = 40) were randomly assigned to normal control, DN, low-dose sitagliptin intervention (ST1), or high-dose sitagliptin intervention (ST2) groups. Animals were euthanized after a 16-week treatment, and blood glucose (BG), glycosylated hemoglobin (HbA1c), urinary albumin excretion rate (AER), serum creatinine (Scr), creatinine clearance rate (Ccr), active glucagon-like peptide-1 (GLP-1) levels, kidney hypertrophy index, and renal pathohistology were determined. Immunohistochemical methods and real-time polymerase chain reaction (PCR) were used to detect protein and mRNA expression of podocalyxin, ERK1/2, GLP-1 receptor (GLP-1R) and transforming growth factor-β (TGF-β). After 16 weeks, BG, AER, Scr, HbA1c and the kidney hypertrophy index were all significantly decreased (p < 0.05) in ST1 and ST2 groups, while Ccr and active GLP-1 levels were increased (p < 0.05), with changes more pronounced in ST2 (p < 0.05). Glomerular pathological lesions were also improved following sitagliptin treatment, especially in ST2. Immunohistochemical and real-time PCR revealed that protein and mRNA expression levels of podocalyxin and GLP-1R were increased significantly in ST1 and ST2, while expression of ERK1/2 and TGF-β was decreased (p < 0.05). Sitagliptin therefore delayed DN progression, possibly via the inhibition of ERK1/2 signaling and promotion of the interaction between GLP-1 and the GLP-1R.

Alleviation of renal mitochondrial dysfunction and apoptosis underlies the protective effect of sitagliptin in gentamicin-induced nephrotoxicity.

This study aimed to investigate the potential protective effect of sitagliptin on gentamicin-induced nephrotoxicity and to elucidate the underlying mechanism. Wistar rats were allocated as follows: Gentamicin group: received gentamicin intraperitoneally (100 mg/kg/day); Gentamicin plus sitagliptin group: received simultaneous gentamicin and sitagliptin (30 mg/kg/day orally); Sitagliptin group: received only sitagliptin; and received saline. Blood urea nitrogen (BUN), serum creatinine, urine protein levels and histopathology of kidney tissues were evaluated. The activity of mitochondrial enzyme complexes reflects the mitochondrial function. Oxidative stress biomarkers and immunohistochemical studies for apoptotic markers caspase-3 and bax were evaluated. Gentamicin causes significant elevation of BUN, serum creatinine and urine proteins. Oxidative stress was revealed by decreased superoxide dismutase activity and catalase activity, glutathione depletion and increased malondialdehyde. Significant decrease in mitochondrial NADH dehydrogenase, succinate dehydrogenase, cytochrome c oxidase and mitochondrial redox activity indicates mitochondrial dysfunction, along with significant elevation in renal caspase-3 and bax. The aforementioned markers and the histological injury in renal tubules were significantly reversed upon sitagliptin treatment. These findings suggest that sitagliptin treatment attenuates renal dysfunction and structural damage through the reduction of oxidative stress, mitochondrial dysfunction and apoptosis in the kidney.

Protective effect of sitagliptin against renal ischemia reperfusion injury in rats

This study was designed to investigate the protective effects of sitagliptin on renal damage induced by renal ischemia reperfusion (I/R) in rats. For this, rats were randomly divided into four groups (n = 8): (1) sham group, in which the rats only underwent right nephrectomy; (2) right nephrectomy and left kidney ischemia (1 h) and reperfusion (24 h) group (I/R); (3) 5 mg/kg sitagliptin administrated group, per-oral once a day for two weeks; (4) 5 mg/kg sitagliptin administrated group, per-oral once a day for two weeks before left kidney I/R (n = 8). Sitagliptin-treated rats that underwent renal I/R demonstrated significant decrease in the serum urea nitrogen and creatinine and also, lipid peroxidation, total oxidant status and malondialdehyde level in the renal tissue when compared to the renal I/R group. Additionally, reduced glutathione, glutathione peroxidase, superoxide dismutase, catalase and total antioxidative capacity were significantly increased after renal I/R in sitagliptin-treated rats. Our histopathological findings were in accordance with these biochemical results. In sum, in the current study all of our results indicated that sitagliptin treatment ameliorated renal damage induced by renal I/R in rats.

Abstract 11558: Sitagliptin Attenuated Brain Damage and Cognitive Impairment in Mice With Chronic Cerebral Hypo-Perfusion Through Suppressing Oxidative Stress and Inflammatory Reaction

Background: Sitagliptin, a new anti-diabetic drug that inhibits dipeptidyl peptidase (DPP)-4 enzyme activity, has been reported to possess neuroprotective property. We tested the protective effect of sitagliptin against chronic cerebral hypoperfusion (CHP) in mice after bilateral carotid artery stenosis (BCAS). Methods: Thirty C57BL/6 mice were divided into three groups: Sham control (SC) (n=10), CHP (n=10), CHP-sitagliptin (orally 600mg/kg/day) (n=10). Working memory was assessed with novel-object recognition test. Magnetic resonance imaging (MRI) was performed at day 0 and day 90 after BCAS procedure prior to sacrifice. Results: Immunohistochemical (IHC) staining showed significantly enhanced microglia activation, astrocytosis, and demyelinating change of white matter in CHP group than in SC but the changes were significantly suppressed after sitagliptin treatment (all p&lt;0.01). The mRNA expressions of inflammatory (TNF-α, MCP-1and MMP-2) and apoptotic (Bax) biomarkers showed an identical pattern, whereas the anti-inflammatory (IL-10) and anti-apoptotic (Bcl-2) biomarkers showed an opposite pattern compared to that of IHC among all groups (all p&lt;0.01). The protein expressions of oxidative stress (NOX-I, NOX-II, nitrotyrosin, oxidized protein), inflammatory (NF-κB, TNF-α and MMP-2), apoptotic (mitochondrial Bax, cleaved PARP), and DNA-damage (γ-H2AX) markers showed an identical pattern, while expression pattern of anti-apoptotic marker (Bcl-2) was opposite to that of IHC (all p&lt;0.01). Glycogen-like peptide-1 receptor protein expression progressively increased from SC to CHP-sitagliptin (p&lt;0.01). The short-term working-memory loss and cortical-matter reduction on MRI-T2 showed a pattern identical to that of IHC in all groups (all p&lt;0.01). Conclusion: Sitagliptin protected against cognitive impairment and brain damage in a murine CHP model. Key words: chronic cerebral hypoperfusion, sitagliptin, oxidative stress inflammation

The dipeptidyl peptidase-4 inhibitor sitagliptin protects against dyslipidemia-related kidney injury in Apolipoprotein E knockout mice.

The goal of this study was to investigate the possible protective effects of sitagliptin against dyslipidemia-related kidney injury in apolipoprotein E knockout (apoE−/−) mice. Eight-week-old male apoE−/− mice were randomized to receive either a high fat diet (HFD, apoE−/− group) or HFD mixed with sitagliptin (sita + apoE−/− group) for 16 weeks. A control group of age- and gender-matched C57BL/6J mice were fed a HFD. The apoE−/− group exhibited increases in body weight and serum lipid levels in addition to high-density lipoprotein, and increases in 24-h urinary 8-hydroxy-2-deoxyguanosine and albuminuria excretion. Decreased insulin sensitivity was also observed in the apoE−/− group. These mice additionally contained enlargements of the glomerular mesangial matrix area, lipid deposition area, and renal interstitium collagen area. The apoE−/− group also demonstrated down-regulation of phosphorylated AMP-activated protein kinase (AMPK), increases in renal mRNA expression of transforming growth factor-beta 1 (TGF-β1) and fibronectin (FN), and increased protein expression of Akt, TGF-β1, FN and p38/ERK mitogen-activated protein kinase (MAPK). Sitagliptin treatment successfully ameliorated all the deleterious effects of dyslipidemia tested. To our knowledge, this is the first time that sitagliptin has been shown to reverse the renal dysfunction and structural damage induced by dyslipidemia in apoE−/− mice. Our results suggest that the renoprotective mechanism of sitagliptin may be due to a reduction in Akt levels, a restoration of AMPK activity, and inhibition of TGF-β1, FN, and p38/ERK MAPK signaling pathways.

Renoprotective effect of sitagliptin against hypertensive nephropathy induced by chronic administration of L-NAME in rats: Role of GLP-1 and GLP-1 receptor

The present study was undertaken to assess the possible protective effects of sitagliptin, a dipeptidyl peptidase 4-inhibitor (DPP4), against Nω-nitro-L-arginine methyl ester (L-NAME) induced hypertensive nephropathy in rats. Hypertension was induced in adult rats by administration of L-NAME for 6 weeks. Rats were treated with sitagliptin (10mg/kg/day or 30mg/kg/day) for six weeks. Chronic L-NAME administration resulted in depletion of serum nitric oxide (NO) associated with elevation in the mean arterial pressure. When compared with the control group; serum urea, serum creatinine, albuminuria, urinary N-acetyl-ß-d-glucosaminidase (NAG) level and renal tissue malondialdhyde (MDA) content were significantly elevated, while creatinine clearance, serum level of glucagon like peptide-1 (GLP-1) as well as renal tissue superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were signifcantly decreased in L-NAME treated group. Renal expression of mRNA for eNOS and GLP-1 receptors were reduced in the L-NAME treated group as compared with the control group. Treatment with sitagliptin (10mg/kg or 30mg/kg) successfully ameliorated the deleterious effects of L-NAME on the all tested parameters. Our study indicates a novel protective effect of sitagliptin against L-NAME induced hypertensive nephropathy. An effect which is mediated through, increasing serum level of GLP-1, upregulation of GLP-1 receptors, which in turn, lead to induction of expression eNOS, increased serum NO level, tandem with decreased lipid perodixation and restore the antioxidant defense mechanisms. It is worth mentioning that the effects produced by sitaglipin (30mg/kg) were superior to the effects obtained by the lower dose.

Protective effects of sitagliptin on myocardial injury and cardiac function in an ischemia/reperfusion rat model

The purpose of this study is to investigate the effects and the underlying mechanisms of sitagliptin pretreatment on myocardial injury and cardiac function in myocardial ischemia/reperfusion (I/R) rat model. The rat model of myocardial I/R was constructed by coronary occlusion. Rats were pretreated with sitagliptin (300mg/kg/day) for 2 weeks, and then subjected to 30min ischemia and 2h reperfusion. The release of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB), cardiac function and cardiomyocyte apoptosis were evaluated. The levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in heart and glucagon-like peptide-1 (GLP-1) level in plasma were measured. Western blot analysis was performed to detect the target proteins of sitagliptin. Our results showed that sitagliptin pretreatment decreased LDH and CK-MB release, and MDA level in I/R rats. More importantly, we revealed for the first time that sitagliptin pretreatment decreased cardiomyocyte apoptosis while increased the levels of GSH-Px and SOD in heart. Sitagliptin also increased GLP-1 level and enhanced cardiac function in I/R rats. Furthermore, sitagliptin pretreatment up-regulated Aktserine473 and Badserine136 phosphorylation, reduced the ratio of Bax/Bcl-2, and decreased expression levels of cleaved caspase-3 and caspase-3. Interestingly, the above observed effects of sitagliptin were all abolished when co-administered with GLP-1 receptor antagonist exendin-(9-39) or PI3K inhibitor LY294002. Taken together, our data indicate that sitagliptin pretreatment could reduce myocardial injury and improve cardiac function in I/R rats by reducing apoptosis and oxidative damage. The underlying mechanism might be the activation of PI3K/Akt signaling pathway by GLP-1/GLP-1 receptor.

The myocardial infarct size-limiting effect of sitagliptin is PKA-dependent, whereas the protective effect of pioglitazone is partially dependent on PKA

Pioglitazone (PIO) and glucagon-like peptide-1 (GLP-1) analogs limit infarct size (IS) in experimental models. The effects of the dipeptidyl-peptidase-IV inhibitors, which increase the endogenous levels of GLP-1, on myocardial protection, are unknown. We studied whether sitagliptin (SIT) and PIO have additive effects on IS limitation in the mouse. Mice received 3-day or 14-day oral SIT (300 mg.kg(-1).day(-1)), PIO (5 mg.kg(-1).day(-1)), SIT + PIO, or vehicle. In addition, mice received intravenous H-89 [20 mg/kg, a protein kinase A (PKA) inhibitor] or vehicle 1 h before ischemia. Rats underwent 30 min myocardial ischemia and 4 h reperfusion. SIT, PIO, and SIT + PIO for 3 days significantly reduced IS (24.3 +/- 2.7, 23.0 +/- 0.8, and 14.7 +/- 0.9%) compared with controls (46.2 +/- 2.8%). H-89 completely blocked the effect of SIT and partially blocked the PIO effect. SIT, but not PIO, increased cAMP levels. PKA activity was increased by PIO and to a greater extent by SIT. PIO, but not SIT, increased cytosolic phospholipase A(2) and cyclooxygenase-2 activity. Accordingly, 6-keto-PGF(1alpha) and 15-deoxy-PGJ(2) increased by PIO but not SIT. In contrast, SIT, and to a lesser extent PIO, increased 15-epi-lipoxin A(4) levels. H-89 completely blocked the effect of SIT and PIO on 15-epi-lipoxin A(4) levels. PIO, and to a greater extent SIT, increased endothelial nitric oxide synthase and cAMP response element-binding protein phosphorylation, an effect that was blocked by H-89. With a 14-day pretreatment experiment, IS was 46.4 +/- 1.0% in the control group, 16.9 +/- 0.6% in SIT (P < 0.001), 19.1 +/- 1.1% in PIO (P = 0.014), and 12.9 +/- 0.7% in SIT + PIO (P < 0.001). We found that SIT and PIO limit IS using different pathways. The protective effect of SIT is via cAMP-dependent PKA activation, whereas PIO mediates its effects via both PKA-dependent and -independent pathways.