Protein Kinase Cβ Isoform Inhibitors

Hydrogen sulfide donor GYY4137 attenuates vascular complications in mesenteric bed of streptozotocin-induced diabetic rats

Hydrogen sulfide (H₂S) has been reported to have beneficial effects in different pathological conditions.

OBJECTIVES

the effects of chronic treatment of diabetic rats with GYY4137 (slow releasing H₂S donor) or NaHS (fast releasing H₂S donor) on the reactivity of the mesenteric bed to vasoactive agonists and the changes in its downstream effectors, ERK1/2 and p38 MAP Kinase have been investigated. In addition, the levels of nitric oxide (NO) and H₂S in all groups were measured.

METHODS

diabetes was induced by a single intraperitoneal (ip) injection of streptozotocin (STZ; 55 mg/kg). Sprague Dawley (SD; n = 10-12/group) rats were randomly divided into six groups: control, STZ-induced diabetic rats, GYY4137-treated control, NaHS-treated control, GYY4137-treated diabetic, and NaHS-treated diabetic. After 28 days of treatment, rats were sacrificed and mesenteric beds were isolated for functional or biochemical studies. The vascular reactivity of the perfused mesenteric bed to norepinephrine, carbachol and sodium nitroprusside were determined by measurement of changes in perfusion pressure. Western blotting was performed to measure the protein expression of ERK1/2, p38, eNOS, and H₂S biosynthesizing enzymes cystathionine-β-synthase and cystathionine-γ-lyase. NO and H₂S levels were measured in all groups in isolated mesenteric tissues or plasma.

RESULTS

diabetes resulted in a significant increase in vasoconstrictor responses to norepinephrine (e.g., 129.6 ± 6.77 mmHg in diabetic vs 89.3 ± 8.48 mmHg in control at 10^-7 dose), and carbachol-induced vasodilation was significantly reduced in diabetic mesenteric bed (e.g., 68.9 ± 4.8 mmHg in diabetic vs 90.6 ± 2.2 mmHg in control at 10^-7 dose). Chronic treatment of the diabetic rats with GYY4137 resulted in a significant improvement in the response to norepinephrine (e.g., 86.66 ± 8.04 mmHg in GYY4137-treated diabetic vs 129.6 ± 6.77 mmHg in untreated diabetic at 10^-7 dose) or carbachol (e.g., 84.90 ± 2.48 mmHg in GYY4137-treated diabetic vs 68.9 ± 4.8 mmHg in untreated diabetic at 10^-7 dose). The biochemical studies showed a marked reduction of the protein expression of ERK and p38 and a significant upregulation of the expression of eNOS and H₂S synthesizing enzymes after chronic treatment with GYY4137. Plasma levels of NO and H₂S were significantly elevated after treatment with GYY4137. However, H₂S production in the mesenteric bed showed a marginal elevation in diabetic tissues compared to controls.

CONCLUSION

the results indicate that GYY4137 may be a novel therapeutic tool to prevent diabetes-associated vascular dysfunction.

Protein kinase C and cardiac dysfunction: a review

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure.

Localization and Interaction between Kinin B1 Receptor and NADPH Oxidase in the Vascular System of Diabetic Rats

Kinin B1 receptor (B1R) enhanced superoxide anion (O2•-) production in the vasculature of diabetic rats. This study investigates the induction and distribution of B1R in diabetic blood vessels and addresses the hypothesis that B1R is co-localized with NADPH oxidase (NOX1 and NOX2) and produces its activation via protein kinase C (PKC). Diabetes was induced in rats with streptozotocin (STZ 65 mg.kg⁻¹, i.p.). Two weeks later, the production of O2•- was measured in aorta rings in response to the B1R agonist (Sar[D-Phe⁸]-des-Arg⁹-BK, 20 μM) by the method of lucigenin-enhanced chemiluminescence. Various inhibitors were added (10 μM) to block PKC_total (Ro-31-8220), PKCβ1/2 (LY333531), or NADPH oxidase (Diphenyleneiodonium). The cellular localization of B1R was studied in the aorta, popliteal artery, and renal glomerulus/arteries by immunofluorescence and confocal microscopy with markers of endothelial cells (anti-RECA-1), macrophages (anti-CD11), vascular smooth muscle cells (anti-SMA), and NADPH oxidase (anti-NOX1 and NOX2). Although B1R was largely distributed in resistant vessels, it was sparsely expressed in the aorta's endothelium. The greater basal production of O2•- in STZ-diabetic aorta was significantly enhanced by the B1R agonist (15–45 min). The peak response to the agonist (30 min) was inhibited by all inhibitors. Immunofluorescent staining for B1R, NOX1, and NOX2 was significantly increased in endothelial cells, vascular smooth muscle cells, and macrophages of STZ-diabetic aorta on which they were found co-localized. Data showed that B1R enhanced O2•- by activating vascular NADPH oxidase through PKCβ1/2. This was substantiated by the cellular co-localization of B1R with NOX1 and NOX2 and opens the possibility that B1R-enhanced oxidative stress is derived from vascular and infiltrating immune cells in diabetes.

Interplay between the kinin B1 receptor and inducible nitric oxide synthase in insulin resistance

BACKGROUND AND PURPOSE

Kinins are vasoactive and pro-inflammatory peptides whose biological effects are mediated by two GPCRs, named B1 and B2 receptors. While the B2 receptor plays a protective role in the cardiovascular system via the activation of endothelial NOS, the B1 receptor is associated with vascular inflammation, insulin resistance and diabetic complications. Because the B1 receptor is a potent activator of the inducible form of NOS (iNOS), this study has addressed the role of iNOS in the deleterious effects of B1 receptors in insulin resistance.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats (50-75 g) had free access to a drinking solution containing 10% d-glucose or tap water (control) for 9 weeks. During the last week, a selective iNOS inhibitor (1400W, 1 mg·kg(-1) twice daily) or its vehicle was administered s.c.

KEY RESULTS

Prolonged glucose treatment caused insulin resistance and several hallmarks of type 2 diabetes. Whereas the treatment with 1400W had no impact on the elevated systolic blood pressure and leptin levels in glucose-fed rats, it significantly reversed or attenuated hyperglycaemia, hyperinsulinaemia, insulin resistance (HOMA index), body weight gain, peroxynitrite formation (nitrotyrosine expression) and the up-regulation of biomarkers of inflammation (B1 receptor, carboxypeptidase M, iNOS and IL-1β) in renal cortex and aorta and to some extent in the liver.

CONCLUSIONS AND IMPLICATIONS

Pharmacological blockade of iNOS prevents the formation of peroxynitrite, which amplifies the pro-inflammatory effects of B1 receptors through a positive feedback mechanism. Hence, targeting iNOS can prevent the deleterious effects of B1 receptors in insulin resistance and peripheral inflammation.

Effect of combined treatment with rosuvastatin and protein kinase Cβ2 inhibitor on angiogenesis following myocardial infarction in diabetic rats

The aim of the present study was to investigate the effects of combined treatment with rosuvastatin and LY333531, a selective protein kinase C (PKC)β2 inhibitor, on angiogenesis under hyperglycemic conditions. Human umbilical vein endothelial cells (HUVECs) cultured in medium containing a normal or high concentration of glucose (33.3 mmol/l) were treated with rosuvastatin (0.1 µmol/l) alone or in combination with LY333531 (10 nmol/l). HUVEC migration and tube formation were assessed. Furthermore, rats with streptozotocin-induced diabetes were randomly divided into groups and treated with either rosuvastatin alone (5 mg/kg/day) or in combination with LY333531 (10 mg/kg/day) for 4 weeks following the induction of myocardial infarction (MI). Echocardiographic patterns, the extent of myocardial fibrosis, capillary density in myocardial tissue, the phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), as well as the expression levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-α (HIF‑1α) were assessed. The results from the in vitro experiment revealed that the tube-forming and migration ability of the HUVECs exposed to high-glucose medium was significantly improved in the group treated with the combination of rosuvastatin and LY333531. In vivo, the combination of rosuvastatin and LY333531 significantly improved left ventricular function, reduced the extent of myocardial fibrosis and increased myocardial capillary density compared to treatment with rosuvastatin alone. In addition, the expression levels of VEGF, and Akt and eNOS phosphorylation were significantly higher in the group exposed to the combination treatment than in the group treated with rosuvastatin alone. The results of the present study indicate that, compared to treatment with rosuvastatin alone, combined treatment with rosuvastatin and LY333531 promotes a greater level of angiogenesis in diabetic rats with MI. This effect is likely mediated through the upregulation of the VEGF‑dependent Akt/eNOS signaling pathway.

Study on the hypoglycemic activities and metabolism of alcohol extract of Alismatis Rhizoma

The Alisma rhizoma is widely used in the therapy of diabetes in traditional folk medicine of China. Compositional analysis of the alcohol extract of Alismatis Rhizoma (AEA) revealed that the eight compounds gotten from AEA are all belonging to protostane-type triterpenes. The AEA and compounds were incubated with 3T3-L1 preadipocytes, glucose level in the 3T3-L1 adipocytes culture medium and lipid content in 3T3-L1 adipocytes were measured, and analysis of alpha-glucosidase inhibition of AEA and compounds. At the same time, the uptake of AEA by 3T3-L1 adipocytes and the metabolism of AEA in SD rats were analyzed by HPLC-ESI/MS. As result, AEA increased glucose uptake in 3T3-L1 adipocyte model, not increase adipogenesis; AEA inhibited alpha-glucosidase activity; alisol A-24-aceate (8) was absorbed by 3T3-L1 adipocytes; and two compounds were detected in blood and three were detected in urine in SD rats. So AEA had protostane-type triterpenes, these type compounds in AEA may have hypoglycemic activity via inhibition of alpha-glucosidase activity and promotion of glucose uptake. In contrast to the anti-diabetic drug thiazolidinediones, they did not induce adipogenesis, avoiding the displeased effects of rosiglitazone.

Increased atherothrombotic burden in patients with diabetes mellitus and acute coronary syndrome: a review of antiplatelet therapy

Patients with diabetes mellitus presenting with acute coronary syndrome have a higher risk of cardiovascular complications and recurrent ischemic events when compared to nondiabetic counterparts. Different mechanisms including endothelial dysfunction, platelet hyperactivity, and abnormalities in coagulation and fibrinolysis have been implicated for this increased atherothrombotic risk. Platelets play an important role in atherogenesis and its thrombotic complications in diabetic patients with acute coronary syndrome. Hence, potent platelet inhibition is of paramount importance in order to optimise outcomes of diabetic patients with acute coronary syndrome. The aim of this paper is to provide an overview of the increased thrombotic burden in diabetes and acute coronary syndrome, the underlying pathophysiology focussing on endothelial and platelet abnormalities, currently available antiplatelet therapies, their benefits and limitations in diabetic patients, and to describe potential future therapeutic strategies to overcome these limitations.

Real-Time Translocation and Function of PKCβII Isoform in Response to Nociceptive Signaling via the TRPV1 Pain Receptor

Serine/threonine protein kinase C βII isoform (PKCβII) or the pain receptor transient receptor potential vanilloid 1 (TRPV1) have been separately implicated in mediating heat hyperalgesia during inflammation or diabetic neuropathy. However, detailed information on the role of PKC βII in nociceptive signaling mediated by TRPV1 is lacking. This study presents evidence for activation and translocation of the PKC βII isoform as a signaling event in nociception mediated by activation of TRPV1 by capsaicin. We show that capsaicin induces translocation of cytosolic PKCβII isoform fused with enhanced green fluorescence protein (PKCβII-EGFP) in dorsal root ganglion (DRG) neurons. We also show capsaicin-induced translocation in Chinese Hamster Ovarian (CHO) cells co-transfected with TRPV1 and PKCβII-EGFP, but not in CHO cells expressing PKCβII-EGFP alone. By contrast, the PKC activator phorbol-12-myristate-13-acetate (PMA) induced translocation of PKCβII-EGFP which was sustained and independent of calcium or TRPV1. In addition PMA-induced sensitization of TRPV1 to capsaicin response in DRG neurons was attenuated by PKCβII blocker CGP 53353. Capsaicin response via TRPV1 in the DRG neurons was confirmed by TRPV1 antagonist AMG 9810. These results suggested a novel and potential signaling link between PKCβII and TRPV1. These cell culture models provide a platform for investigating mechanisms of painful neuropathies mediated by nociceptors expressing the pain sensing gene TRPV1, and its regulation by the PKC isoform PKCβII.

Endothelial dysfunction in diabetes mellitus: molecular mechanisms and clinical implications

Cardiovascular disease is a major complication of diabetes mellitus, and improved strategies for prevention and treatment are needed. Endothelial dysfunction contributes to the pathogenesis and clinical expression of atherosclerosis in diabetes mellitus. This article reviews the evidence linking endothelial dysfunction to human diabetes mellitus and experimental studies that investigated the responsible mechanisms. We then discuss the implications of these studies for current management and for new approaches for the prevention and treatment of cardiovascular disease in patients with diabetes mellitus.

The role of inflammatory cytokines in diabetes and its complications

The prevalence of diabetes worldwide is increasing rapidly in association with the increase in obesity. Complications are a major fear of patients with diabetes. Complications of diabetes affect many tissues and organs, causing retinopathy, nephropathy, neuropathy, cardiovascular diseases, peripheral vascular diseases, stroke, and periodontal pathologies. Immunologic abnormalities are associated with type 1 and type 2 diabetes and diabetic complications. T cell abnormalities are believed to be the major cause of autoimmune disease in type 1 diabetes, leading to the destruction of pancreatic islets. In type 2 diabetes, inflammation and activation of monocytes are postulated to be important for enhancing insulin resistance and may contribute to the loss of insulin secretory function by islet cells. Many factors can enhance insulin resistance, including genetics, a sedentary lifestyle, obesity, and other conditions, such as chronic inflammation or infection. Increases in inflammation, such as activation of monocytes and increased levels of inflammatory markers, e.g., C-reactive protein, plasminogen activator inhibitor-1, and other cytokines, were reported in insulin-resistant states without diabetes. One possible mechanism is that abnormal levels of metabolites, such as lipids, fatty acids, and various cytokines from the adipose tissue, activate monocytes and increase the secretion of inflammatory cytokines, enhancing insulin resistance. According to this model, obesity activates monocytes and enhances insulin resistance, increasing the risk for type 2 diabetes. Abnormalities in innate immunity might also participate in the development of diabetic complications. In general, hyperglycemia is the main initiator of diabetic retinopathy, nephropathy, and neuropathy, and it participates in the development of diabetic cardiovascular diseases. Although the precise role of inflammation in the development of diabetic microvascular diseases is still unclear, it is likely that inflammation induced by diabetes and insulin resistance can accelerate atherosclerosis in patients with diabetes. Also, it was shown that conditions with an inflammatory basis, such as obesity and type 2 diabetes, can contribute to periodontal disease, suggesting that periodontal abnormalities may be partly influenced by inflammatory changes. Further research is required to confirm the role of inflammation and the onset of diabetes, microvascular diseases, and periodontal pathologies.

Prevalence, awareness, treatment, and control of hypertension in the Jackson Heart Study

African Americans have higher reported hypertension prevalence and lower control rates than other ethnic groups in the United States. Hypertension prevalence, awareness, treatment, and control (outcomes) and potentially associated demographic, lifestyle, comorbidity, and health care access factors were examined in 5249 adult participants (3362 women and 1887 men) aged 21 to 94 years enrolled in the Jackson Heart Study. Hypertension prevalence (62.9%), awareness (87.3%), treatment (83.2%), and control (66.4%) were high. Control declined with advancing age; estimates for all of the outcomes were higher for women compared with men. Lower socioeconomic status was associated with prevalence and control. Smoking was negatively associated with awareness and treatment, particularly among men. Comorbidities (diabetes, chronic kidney disease, and cardiovascular disease), likely driven by the high rates of obesity, correlated with hypertension prevalence, awareness, treatment, and control. Lack of health insurance was marginally associated with poorer control, whereas use of preventive care was positively associated with prevalence, awareness, and treatment, particularly among men. In comparisons with the 1994-2004 National Health and Nutrition Examination Survey data adjusted to Jackson Heart Study sex, age, and socioeconomic status distribution, control rates among Jackson Heart Study participants appeared to be higher than in their national counterparts and similar to that of whites. These results suggest that public health efforts to increase awareness and treatment among African Americans have been relatively effective. The Jackson Heart Study data indicate that better control rates can be achieved in this high-risk population.

Treating insulin resistance: future prospects

Insulin resistance typically reflects multiple defects of insulin receptor and post-receptor signalling that impair a diverse range of metabolic and vascular actions. Many potential intervention targets and compounds with therapeutic activity have been described. Proof of principle for a non-peptide insulin mimetic has been demonstrated by specific activation of the intracellular B-subunit of the insulin receptor. Potentiation of insulin action has been achieved with agents that enhance phosphorylation and prolong the tyrosine kinase activity of the insulin receptor and its protein substrates after activation by insulin. These include inhibitors of phosphatases and serine kinases that normally prevent or terminate tyrosine kinase signalling. Additional approaches involve increasing the activity of phosphatidylinositol 3-kinase and other downstream components of the insulin signalling pathways. Experimental interventions to remove signalling defects caused by cytokines, certain adipocyte hormones, excess fatty acids, glucotoxicity and negative feedback by distal signalling steps have also indicated therapeutic possibilities. Several hormones, metabolic enzymes, minerals, co-factors and transcription co-activators have shown insulin-sensitising potential. Since insulin resistance affects many metabolic and cardiovascular diseases, it provides an opportunity for simultaneous therapeutic attack on a broad front.

Long-Term and Short-Term Changes in Antihypertensive Prescribing by Office-Based Physicians in the United States

Medication choices for the treatment of elevated blood pressure have a large potential impact on both patient outcomes and health care costs. Historic trends of prescribing for hypertension will advance the understanding of physician practice of evidence-based medicine. This study describes both long- and short-term trends in US antihypertensive prescribing from 1990 through 2004. Data were extracted from the National Disease and Therapeutic Index, a continuing survey of a national sample of US office-based physicians. Cox and Stuart and z tests were performed. Diuretics ranked among the top 3 antihypertensive drug classes throughout the entire study time span. Angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers (CCBs) were preferred over diuretics beginning in 1993, with diuretics surpassing CCBs in 2000. β-Blockers were consistently the fourth most common class until 2002, when exceeded by angiotensin II receptor antagonists (ARBs). Most recent trends indicated an immediate but short-lived increase in the prescription of thiazide diuretics after the new clinical evidence released in December 2002 demonstrating clinical equivalence of thiazides to ACE inhibitors and CCBs. In contrast, prescription of ACE inhibitors declined, accompanied by continuation of a pre-existing increase in the prescription of ARBs, whereas prescription of CCBs remained essentially stable after the new evidence was released. The recorded long- and short-term trends indicate that evidence-based clinical recommendations had an impact on antihypertensive prescribing practices, but the magnitude of impact may be smaller and of more limited duration than desired.

Characterization of a novel protein kinase D: Caenorhabditis elegans DKF-1 is activated by translocation-phosphorylation and regulates movement and growth in vivo

Protein kinase D (PKD) isoforms are protein kinase C (PKC) effectors in diacylglycerol (DAG)-regulated signaling pathways. Key physiological processes are placed under DAG control by the distinctive substrate specificity and intracellular distribution of PKDs. Comprehension of the roles of PKDs in homeostasis and signal transduction requires further knowledge of regulatory interplay among PKD and PKC isoforms, analysis of PKC-independent PKD activation, and characterization of functions controlled by PKDs in vivo. Caenorhabditis elegans and mammals share conserved signaling mechanisms, molecules, and pathways Thus, characterization of the C. elegans PKDs could yield insights into regulation and functions that apply to all eukaryotic PKDs. C. elegans DKF-1 (D kinase family-1) contains tandem DAG binding (C1) modules, a PH (pleckstrin homology) domain, and a Ser/Thr protein kinase segment, which are homologous with domains in classical PKDs. DKF-1 and PKDs have similar substrate specificities. Phorbol 12-myristate 13-acetate (PMA) switches on DKF-1 catalytic activity in situ by promoting phosphorylation of a single amino acid Thr(588) in the activation loop. DKF-1 phosphorylation and activation are unaffected when PKC activity is eliminated by inhibitors. Both phosphorylation and kinase activity of DKF-1 are extinguished by substituting Ala for Thr(588) or Gln for Lys(455) ("kinase dead") or incubating with protein phosphatase 2C. Thus, DKF-1 is a PMA-activated, PKC-independent D kinase. In vivo, dkf-1 gene promoter activity is evident in neurons. Both dkf-1 gene disruption (null phenotype) and RNA interference-mediated depletion of DKF-1 protein cause lower body paralysis. Targeted DKF-1 expression corrected this locomotory defect in dkf-1 null animals. Supraphysiological expression of DKF-1 limited C. elegans growth to approximately 60% of normal length.

The pathogenesis of myocardial fibrosis in the setting of diabetic cardiomyopathy

Diabetes has emerged as a major threat to worldwide health. The increasing incidence of diabetes in young individuals is particularly worrisome given that the disease is likely to evolve over a period of years. In 1972, the existence of a diabetic cardiomyopathy was proposed based on the experience with four adult diabetic patients who suffered from congestive heart failure in the absence of discernible coronary artery disease, valvular or congenital heart disease, hypertension, or alcoholism. The exact mechanisms underlying the disease are unknown; however, an important component of the pathological alterations observed in these hearts includes the accumulation of extracellular matrix (ECM) proteins, in particular collagens. The excess deposition of ECM in the heart mirrors what occurs in other organs such as the kidney and peritoneum of diabetics. Mechanisms responsible for these alterations may include the excess production, reduced degradation, and/or chemical modification of ECM proteins. These effects may be the result of direct or indirect actions of high glucose concentrations. This article reviews our state of knowledge on the effects that diabetes-like conditions exert on the cells responsible for ECM production as well as relevant experimental and clinical data.

Protein kinase cascades in the regulation of cardiac hypertrophy

In broad terms, there are 3 types of cardiac hypertrophy: normal growth, growth induced by physical conditioning (i.e., physiologic hypertrophy), and growth induced by pathologic stimuli. Recent evidence suggests that normal and exercise-induced cardiac growth are regulated in large part by the growth hormone/IGF axis via signaling through the PI3K/Akt pathway. In contrast, pathological or reactive cardiac growth is triggered by autocrine and paracrine neurohormonal factors released during biomechanical stress that signal through the Gq/phospholipase C pathway, leading to an increase in cytosolic calcium and activation of PKC. Here we review recent developments in the area of these cardiotrophic kinases, highlighting the utility of animal models that are helping to identify molecular targets in the human condition.

Upregulation of placental growth factor by vascular endothelial growth factor via a post-transcriptional mechanism

Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are key angiogenic stimulators during normal development and wound healing, as well as in a variety of pathological conditions. Recent studies have demonstrated a synergistic effect of VEGF and PlGF in pathological angiogenesis and suggest a role for PlGF in amplifying VEGF action in endothelial cells. We show here in the mouse model of oxygen-induced retinopathy that VEGF is significantly increased (P<0.01) in the retina at both the mRNA and protein levels. In this mouse model, PlGF was significantly upregulated in the retina at the protein level (P<0.01) without a corresponding change in mRNA levels. In cultured human retinal and umbilical vein endothelial cells, VEGF induced the production of PlGF protein by over 10-fold (P<0.01) in a dose-dependent manner through a post-transcriptional mechanism. The increased PlGF expression upon VEGF treatment was significantly reduced by inhibition of the protein kinase C (PKC) and MEK signaling pathways, as well as by treatment with the calcium ionophore A23187. Taken together, our findings demonstrate that VEGF can amplify its effects on endothelial cells by inducing the production of PlGF via a post-transcriptional mechanism in a PKC-dependent manner, and provide a potential link between PKC inhibition and amelioration of vascular complications in the development of angiogenic diseases.