Effect of GLP-1 Receptor Agonist on Ischemia Reperfusion Injury in Rats with Metabolic Syndrome.

Metabolic syndrome (MetS) represents an important factor that increases the risk of myocardial infarction, and more severe complications. Glucagon Like Peptide-1 Receptor Agonists (GLP-1RAs) exhibit cardioprotective potential, but their efficacy in MetS-related myocardial dysfunction has not been fully explored. Therefore, we aimed to assess the effects of exenatide and dulaglutide on heart function and redox balance in MetS-induced rats. Twenty-four Wistar albino rats with induced MetS were divided into three groups: MetS, exenatide-treated (5 µg/kg), dulaglutide-treated (0.6 mg/kg). After 6 weeks of treatment, in vivo heart function was assessed via echocardiography, while ex vivo function was evaluated using a Langendorff apparatus to simulate ischemia-reperfusion injury. Heart tissue samples were analyzed histologically, and oxidative stress biomarkers were measured spectrophotometrically from the coronary venous effluent. Both exenatide and dulaglutide significantly improved the ejection fraction by 3% and 7%, respectively, compared to the MetS group. Histological analyses corroborated these findings, revealing a reduction in the cross-sectional area of cardiomyocytes by 11% in the exenatide and 18% in the dulaglutide group, indicating reduced myocardial damage in GLP-1RA-treated rats. Our findings suggest strong cardioprotective potential of GLP-1RAs in MetS, with dulaglutide showing a slight advantage. Thus, both exenatide and dulaglutide are potentially promising targets for cardioprotection and reducing mortality in MetS patients.

Effects of Different Therapeutic Approaches on Redox Balance in Psoriatic Patients.

Given that oxidative stress represents an important etiological factor in the pathogenesis of psoriasis, the aim of this study was to assess the effects of different therapeutic approaches, methotrexate, secukinumab, and ustekinumab on systemic oxidative stress biomarkers in psoriatic patients. This study involved 78 psoriatic patients, divided into the group treated with methotrexate (23 patients), secukinumab (28 patients), and ustekinumab (27 patients), and 15 healthy controls. Oxidative stress biomarkers (index of lipid peroxidation measured as TBARS, nitrites (NO2-), superoxide anion radical (O2-), and hydrogen peroxide (H2O2)) and antioxidative defense system (superoxide dismutase (SOD) activity, catalase (CAT) activity, and reduced glutathione (GSH)) were determined spectrophotometrically from the blood before the initiation of therapy in 16th, 28th, and 52nd week. O2- and SOD showed the most prominent changes comparing the psoriatic patients and healthy controls. CAT activity was significantly lower in psoriatic patients, and methotrexate induced a further decline in CAT activity. Ustekinumab induced a significant increase in GSH level after 52 weeks of treatment, while methotrexate reduced GSH. All applied therapeutic options induced a reduction in PASI, BSA, DLQI, and EARP. Biological drugs exert more pronounced antioxidant effects compared to methotrexate, which is most clearly observed in the values of O2- and SOD.

Sacubitril/valsartan promotes white adipose tissue browning in rats with metabolic syndrome through activation of mTORC1.

In addition to their usual use in the treatment of cardiovascular disease, weak evidence is available for the potential of combined use of neprilysin inhibitor (sacubitril) and AT1 receptor antagonist (valsartan) to promote browning of white adipose tissue (WAT) in rats with metabolic syndrome (MetS). This study involved 32 male Wistar albino rats divided into four groups: CTRL-healthy control rats; ENT-healthy rats treated with sacubitril/valsartan; MS-rats with MetS; MS + ENT-rats with MetS treated with sacubitril/valsartan. After finishing the experimental protocol, different WAT depots were isolated for further analysis of molecular pathways. Molecular docking and molecular dynamics studies were used for in silico assessment of the binding affinity of sacubitril and valsartan towards subunits of mechanistic target of rapamycin complex 1 (mTORC1). Sacubitril/valsartan treatment markedly diminished morphological changes in adipose tissue, resulting in smaller lipid size and multilocular lipid droplet structure in WAT. We showed significantly higher protein expression of uncoupling protein-1 (UCP-1) and mTORC1 in WAT of MS + ENT rats, correlating with increased relative gene expression of browning-related markers in tissue of rats treated with sacubitril/valsartan compared with MS group of rats. In silico analysis showed that sacubitrilat and valsartan exhibited the highest binding affinity against mTOR and mLST8, forming stable complexes with these mTORC1 subunits. The observed results confirmed strong potential of combined sacubitril/valsartan treatment to increase browning markers expression in different WAT depots in MetS condition and to form permanent complexes with mTOR and mLST8 subunits over the time.

Integrin ß3 directly inhibits the Gα13-p115RhoGEF interaction to regulate G protein signaling and platelet exocytosis.

The integrins and G protein-coupled receptors are both fundamental in cell biology. The cross talk between these two, however, is unclear. Here we show that ß3 integrins negatively regulate G protein-coupled signaling by directly inhibiting the Gα13-p115RhoGEF interaction. Furthermore, whereas ß3 deficiency or integrin antagonists inhibit integrin-dependent platelet aggregation and exocytosis (granule secretion), they enhance G protein-coupled RhoA activation and integrin-independent secretion. In contrast, a ß3-derived Gα13-binding peptide or Gα13 knockout inhibits G protein-coupled RhoA activation and both integrin-independent and dependent platelet secretion without affecting primary platelet aggregation. In a mouse model of myocardial ischemia/reperfusion injury in vivo, the ß3-derived Gα13-binding peptide inhibits platelet secretion of granule constituents, which exacerbates inflammation and ischemia/reperfusion injury. These data establish crucial integrin-G protein crosstalk, providing a rationale for therapeutic approaches that inhibit exocytosis in platelets and possibly other cells without adverse effects associated with loss of cell adhesion.

Variations of Redox Balance in Different Stages of Childhood Immune Thrombocytopenic Purpura.

BACKGROUND: Few previous studies indicated the role of oxidative stress in the pathogenesis of childhood idiopathic thrombocytopenic purpura (ITP), but there are little data regarding changes in redox balance in different forms of the disease, and changes after therapeutic procedures. We aimed to investigate the values of pro-oxidants and antioxidative capacity in various forms of ITP before and after the applying therapy. MATERIALS AND METHODS: The research included 102 children, classified into the following groups: (1) newly diagnosed ITP (ndITP), (2) persistent ITP, (3) chronic ITP (chITP), and (4) control groups: (A) healthy control and (B) previously experienced ITP-healthy children who had been suffering from ITP earlier. During the clinical assessment, a blood sample was taken from the patients, from which the value of pro-oxidants (index of lipid peroxidation measured as TBARS, nitrites [NO2 -], as measurement of nitric oxide [NO] production, superoxide anion radical [O2 -], and hydrogen peroxide [H2O2]) and the capacity of antioxidant protection (activity of superoxide dismutase and catalase, and quantity of reduced glutathione) were determined spectrophotometrically. RESULTS: Our results demonstrated that values of pro-oxidants, especially reflected through the TBARS and O2 -, were the highest in the ndITP and exacerbated chITP groups. Also, the activity of the endogenous antioxidative defense system was the lowest in these groups. Intravenous immunoglobulin therapy in the ndITP group exerted the most prominent effect on the redox balance. CONCLUSION: It can be concluded that severity and exacerbation of the ITP are closely related to the redox status.

Predictors of Non-Adherence to Medications in Hypertensive Patients.

Background: Elevated blood pressure (BP) is one of the leading causes for developing major cardiovascular events and still represents a major public health challenge worldwide. We aimed to provide data on predictors of poor adherence to medication in hypertensive patients in Serbia. Methods: Observational, analytical study was undertaken at a group of 388 patients who refilled their medications in the Pharmacy Institution, "Apoteka Kragujevac", Kragujevac, Serbia between Jan and Mar 2019. Afterward, we conducted a case-control study to evaluate the influence of the variables associated with the adherence. We used a self-developed questionnaire and SF-36 to assess the influence of the quality of life on medication adherence. Results: Results revealed four independent predictors of non-adherence: increased number of medications, living in a city, forgetfulness of the dosing regimen and low energy. The odds of non-adherence were the highest among the participants living in the city and the low energy was the only factor inversely associated with the level of non-adherence. Conclusion: Many factors were associated with the non-adherence to medication. Further studies are needed to find the most appropriate protocol to promote adherence. The four risk factors (increased number of medications, living in a city, forgetfulness of the dosing regimen and low energy) are associated with non-adherence in adult hypertensive patients.

The Challenges of Caregivers of Children with Autism Spectrum Disorders Comorbidity during the COVID-19 Pandemic in Serbia.

BACKGROUND: Children with Autism Spectrum Disorders (ASD) experience significantly higher prevalence of other mental disorders, which amplifies their need for overall support. The outbreak of novel coronavirus (COVID-19) resulted in restrictions and limited access to different services with great challenge for families and children with ASD. SUBJECTS AND METHODS: We used an electronic SurveyMonkey questionnaire to examine the experiences of 114 caregivers of children with ASD. We compared: (a) level of support by the child's school, changes in child behavior, and priority needs for families of ASD and ASD with comorbidities (ASD+) children, during pandemic, and (b) developmental history and diagnosis for ASD and ASD+ children before the pandemic. RESULTS: Our research shows significant behavioral difficulties in the population with ASD and ASD+ that arose in the field of altered living conditions and overall functioning during the COVID-19 pandemic. Statistically significant results comparing ASD to ASD+ children we found in area of getting additional help and support before the outbreak of the pandemic (47.1% vs 16.0%, p=0.002), as well as in worsening of sleep problems, statistically significant more common in children with ASD+ (ASD+ 47.7% vs. ASD 25.7%, p=0.046). CONCLUSIONS: Our findings can contribute to the faster development and implementation of protocols for dealing with situations such as pandemics, related to the vulnerable population of children with ASD and their caregivers.

Increased Expression of Extracellular Vesicles Is Associated With the Procoagulant State in Patients With Established Rheumatoid Arthritis.

This study sought to identify different subpopulations of extracellular vesicles (EVs) in plasma from female patients with established rheumatoid arthritis (RA) in relation to the activation of coagulation and fibrin formation in these patients. Forty women were included in the study, 20 patients and 20 age-matched healthy controls. The mean disease duration in patients was 13.0 (5.0-25.0) years, with medium to high disease activity despite ongoing treatment with low-dose prednisolone and methotrexate. There were no differences between the investigated groups regarding the presence of traditional cardiovascular risk factors. The concentration of phosphatidylserine-positive (PS+) EVs; platelet (CD42a+), leucocyte (CD45+), monocyte (CD14+), and endothelial (CD144+)-derived EVs; and EVs-expressing tissue factor (CD142+), P-selectin (CD62P+), and E-selectin (CD62E+) were determined by flow cytometry analysis. Overall hemostasis potential (OHP) was assessed to follow the hemostatic disturbances, including the parameters for overall coagulation potential (OCP) and overall fibrinolytic potential (OFP). Fibrin clot turbidity was measured together with clot lysis time, and scanning electron microscopy was performed. Increased concentrations of PS+, CD42a+, CD142+, CD45+, CD14+, and CD62P+ EVs were found in plasma from patients with RA compared to healthy controls, and the concentrations of PS+, CD42a+, CD14+, and CD62P+ EVs were positively correlated with the inflammatory parameters in RA patients. Positive correlations were also found between the levels of PS+ and CD42a+ EVs and OCP as well as between the levels of PS+, CD42a+, and CD62P+EVs and OHP. The levels of PS+, CD42a+, CD14+, CD62P+, and CD62E+ EVs were negatively correlated with OFP. Elevated levels of circulating EVs of different cell origins were found in patients with established RA, in relation to the inflammatory burden and coagulation activation in the disease.

The Influence of Menopause and Inflammation on Redox Status and Bone Mineral Density in Patients with Rheumatoid Arthritis.

Although oxidative stress is considered to be one of the key pathogenic factors in rheumatoid arthritis (RA), there is insufficient knowledge regarding the impact of menopause on redox status in this population. Thus, this study is aimed at assessing the influence of menopause within healthy women and within RA patients as well as the impact of RA in premenopausal and postmenopausal women on redox status, with special reference to bone mineral density (BMD). A total of 90 women were included in the study, 42 with RA and 48 age-matched healthy controls. They were divided into subgroups according to the presence of menopause. Following oxidative stress parameters were measured spectrophotometrically: index of lipid peroxidation (measured as TBARS), nitrites (NO2 -), superoxide anion radical (O2 -), hydrogen peroxide (H2O2), superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH). BMD was assessed by using a dual-energy X-ray absorptiometry scanner. Comorbidities and drug history were recorded. The levels of H2O2 and TBARS were elevated in patients with RA, while NO2 - and O2 - increased in healthy women, both in premenopausal and postmenopausal groups. SOD activity decreased in postmenopausal RA patients. BMD was reduced in postmenopausal RA women. There was a correlation between NO2 - and O2 - with Health Assessment Questionnaire (HAQ) index in RA patients. Given that postmenopausal state was associated with elevated oxidative stress within healthy women and that menopausal state did not affect redox homeostasis within RA patients, but the redox homeostasis was altered in both RA groups compared to healthy women, it can be presumed that impaired redox status in RA occurred due to presence of the disease, irrespective of age. Moreover, menopause attenuates BMD reduction in women with RA. These results may indicate the need for therapeutic use of antioxidants in the form of supplements in women with RA, regardless of age.

Dipeptidyl peptidase-4 inhibitors as new tools for cardioprotection.

Previous studies have demonstrated that individuals with type 2 diabetes mellitus (T2DM) have a two- to fourfold propensity to develop cardiovascular disease (CVD) than nondiabetic population, making CVD a major cause of death and disability among people with T2DM. The present treatment options for management of diabetes propose the earlier and more frequent use of new antidiabetic drugs that could control hyperglycaemia and reduce the risk of cardiovascular events. Findings from basic and clinical studies pointed out DPP-4 inhibitors as potentially novel pharmacological tools for cardioprotection. There is a growing body of evidence suggesting that these drugs have ability to protect the heart against acute ischaemia-reperfusion injury as well as reduce the size of infarction. Consequently, the prevention of degradation of the incretin hormones by the use of DPP-4 inhibitors represents a new strategy in the treatment of patients with T2DM and reduction of CV events in these patients. Here, we discuss the cardioprotective effects of DPP-4 inhibitors as well as proposed pathways that these hypoglycaemic agents target in the cardiovascular system.

Correlation of Redox Status with Procalcitonin and C-reactive Protein in Septic Patients.

Based on the role of oxidative stress in the pathophysiological mechanisms of sepsis and the importance of PCT as a clinically applicable biomarker for early detection of inflammatory response initiation, we aimed this study at examining the correlation between PCT levels and oxidative stress parameters (prooxidants and antioxidants) in patients with sepsis. This study was designed as a case-series prospective clinical study which involved 103 critically ill patients and 17 healthy participants with diagnosis of sepsis/septic shock (over 18 years of age, both gender) admitted to the Intensive Care Unit (ICU) of Valjevo General Hospital in Serbia. All subjects were divided into patients who were operated on/underwent surgery before sampling and have sepsis (n = 24), patients who were operated on/underwent surgery before sampling and have septic shock (n = 25), patients who were not operated on/did not undergo surgery before sampling and have sepsis (n = 26), patients who were not operated on/did not undergo surgery before sampling and have septic shock (n = 28), and participants who are healthy (n = 17). PCT has confirmed a positive correlation with prooxidants and type of critical illness, and performing surgical intervention diminished oxidative stress in patients with septic shock. Prognosis in critically ill patients was strongly associated with PCT levels but not with nonspecifically C-reactive protein.

The Role of Cardiac N-Methyl-D-Aspartate Receptors in Heart Conditioning-Effects on Heart Function and Oxidative Stress.

As well as the most known role of N-methyl-D-aspartate receptors (NMDARs) in the nervous system, there is a plethora of evidence that NMDARs are also present in the cardiovascular system where they participate in various physiological processes, as well as pathological conditions. The aim of this study was to assess the effects of preconditioning and postconditioning of isolated rat heart with NMDAR agonists and antagonists on heart function and release of oxidative stress biomarkers. The hearts of male Wistar albino rats were subjected to global ischemia for 20 min, followed by 30 min of reperfusion, using the Langendorff technique, and cardiodynamic parameters were determined during the subsequent preconditioning with the NMDAR agonists glutamate (100 µmol/L) and (RS)-(Tetrazol-5-yl)glycine (5 µmol/L) and the NMDAR antagonists memantine (100 µmol/L) and MK-801 (30 µmol/L). In the postconditioning group, the hearts were perfused with the same dose of drugs during the first 3 min of reperfusion. The oxidative stress biomarkers were determined spectrophotometrically in samples of coronary venous effluent. The NMDAR antagonists, especially MK-801, applied in postconditioning had a marked antioxidative effect with a most pronounced protective effect. The results from this study suggest that NMDARs could be a potential therapeutic target in the prevention and treatment of ischemic and reperfusion injury of the heart.

Perceptions on Support, Challenges and Needs among Parents of Children with Autism: the Serbian Experience.

BACKGROUND: Autism spectrum disorders (ASD) significantly impact lives of affected individuals and their families. They confront daunting challenges and multiple demands in their daily life, when compared to parents of children with other disabilities or parents of typically developing children. SUBJECTS AND METHODS: Participants completed The Caregiver Needs Survey, the survey intended for parents or primary caregivers of children with a diagnosis of ASD. During the study, 231 parents were interviewed; 167 mothers and 64 fathers. Parents were recruited from the patient database comprised of families from the two largest cities in Serbia. All of them were contacted before the study, either via phone or at the child's regular check-in visit. RESULTS: Over 90 percent of the parents reported that additional support at schools, home, and improved relationships with service providers are necessary and important. The most important challenges related to care were child's communication difficulties, social interaction difficulties, and problems with daily living skills. The significant predictors of lower overall satisfaction were parent's higher education, having a first concern related to problems of the child's interaction with others or playing alone, and parent frustration with accessing services in the past 12 months. Greater overall satisfaction, on the other hand, was related to having an in-school tutor training or assistance in managing child's needs or implementing treatments, and having primary care doctor or pediatrician as a source of information on autism. CONCLUSIONS: Future efforts to develop ASD-related policies and services should also take the following into consideration: the low level of awareness among caregivers and health care providers about the early signs of autism; disparities in access to services; educational problems and significant levels of dissatisfaction with the overall care and stigma.

Outcome differences between simple and complex gastroschisis.

BACKGROUND: We reviewed differences of the outcome of newborn with simple and complex gastroschisis treated at our institution over the past fifteen years. METHODS: A retrospective cohort study was performed on all infants with gastroschisis treated at the Institute for mother and child health care, Belgrade, between 2001 and 2015 (n=70). Premature infants (<34 weeks of gestation) and babies with birth weight less than 1500 g were excluded (n=5). We compared outcomes in infants with simple gastroschisis and those with complex gastroschisis. An outcome analysis was performed for birth weight, gestational age, gender, mode of defect closure, presence of intestinal necrosis or perforation, reoperation, duration of mechanical ventilation and total parenteral nutrition, presence of bowel pseudoopstraction, sepsis, total duration of hospital stay, mortality rates. RESULTS: Of 65 patients, 15 (23,07%) had complex gastroschisis, including atresia 5 patients (33,3%), ischemic complication 9 patients (60%) and one patient with closing gastroschisis (6,66%). Sixty eight percent underwent primary closure.There was difference between the simple and the complex gastroschisis in duration of mechanical ventilation (P= ,000003), total parenteral nutrition (P= ,000019), bowel pseudoobstruction (P= ,00067), reoperation (P= ,00122), sepsis (P= ,0043), hospital stay (P= ,000198). In the simple gastroschisis group 92% of patients survived to discharge. In the complex gastroschisis group 3 patients died in hospital (P= ,338). CONCLUSIONS: More research should be focused to predict complex gastroschisis and to improve prenatal diagnosis and postnatal management, without a significant increase in morbidity and mortality. KEY WORDS: Complex, Gastroschisis, Outcomes, Simple, Vanishing.

Gastroschisis with gastric perforation and jejunal stenosis A rare association of anomalies.

AIM: Gastroschisis with prenatal gastric perforation and intestinal stenosis is a rare and serious anomaly. although there are several case reports, no case series exists to suggest the prognosis for these infants. MATERIAL AND METHODS: In this report a case of gastroschisis with gastric perforation and jejunal stenosis in male newborn is presented with literature review. The stomach, small bowel and the part of the colon were herniated through the abdominal wall defect. A large perforation site at the anterior wall of fundus and a thin fibrous strip that causing stenosis of jejunum was found. RESULTS: Gastrorraphy was performed. Stenosis of jejunum was resected and t-t anastomosis was performed, followed by primary fascial closure. DISCUSSION: The prenatal sonographic finding of bowel or gastric perforation are variable. Antenatal bowel dilatation and in particular intraabdominal bowel dilatation is prognostically useful for detection of patients with worse outcome. The absence of bowel dilatation cannot fully exclude complex patients. Early restoration of bowel continuity using primary anastomosis and primary abdominal wall closure are not associated with prolonged time for full enteral feeding and length of hospital stay. CONCLUSIONS: We have presented the first detailed report of surgical intervention and outcomes in case of gastroschisis with prenatal gastric perforation and congenital jejunal stenosis. Early restoration of bowel continuity using primary anastomosis and primary abdominal wall closure is recommended here. More research should be focused to predict complex gastroschisis and to improve prenatal diagnosis and postnatal management, without a significant increase in morbidity and mortality. KEY WORDS: Gastroschisis, Gastric perforation, Stenosis of jejunum.

Gastroschisis with gastric perforation and jejunal stenosis. A rare association of anomalies.

AIM: Gastroschisis with prenatal gastric perforation and intestinal stenosis is a rare and serious anomaly. although there are several case reports, no case series exists to suggest the prognosis for these infants. MATERIAL AND METHODS: In this report a case of gastroschisis with gastric perforation and jejunal stenosis in male newborn is presented with literature review. The stomach, small bowel and the part of the colon were herniated through the abdominal wall defect. A large perforation site at the anterior wall of fundus and a thin fibrous strip that causing stenosis of jejunum was found. RESULTS: Gastrorraphy was performed. Stenosis of jejunum was resected and t-t anastomosis was performed, followed by primary fascial closure. DISCUSSION: The prenatal sonographic finding of bowel or gastric perforation are variable. Antenatal bowel dilatation and in particular intraabdominal bowel dilatation is prognostically useful for detection of patients with worse outcome. The absence of bowel dilatation cannot fully exclude complex patients. Early restoration of bowel continuity using primary anastomosis and primary abdominal wall closure are not associated with prolonged time for full enteral feeding and length of hospital stay. CONCLUSIONS: We have presented the first detailed report of surgical intervention and outcomes in case of gastroschisis with prenatal gastric perforation and congenital jejunal stenosis. Early restoration of bowel continuity using primary anastomosis and primary abdominal wall closure is recommended here. More research should be focused to predict complex gastroschisis and to improve prenatal diagnosis and postnatal management, without a significant increase in morbidity and mortality. KEY WORDS: Gastroschisis, Gastric perforation, Stenosis of jejunum.

Heat-shock protein gp96/grp94 is an essential chaperone for the platelet glycoprotein Ib-IX-V complex.

The platelet glycoprotein Ib-IX-V complex (GPIb-IX-IV) is the receptor for VWF and is responsible for VWF-mediated platelet activation and aggregation. Loss of the GPIb-IX-V complex is pathogenic for Bernard-soulier Syndrome (BSS), which is characterized by macrothrombocytopenia and impaired platelet function. It remains unclear how the GPIb-IX-V complex is assembled and whether there is a role for a specific molecular chaperone in the process. In the present study, we report that the assembly of the GPIb-IX-V complex depends critically on a molecular chaperone in the endoplasmic reticulum (ER): gp96 (also known as grp94 and HSP90b1). gp96/grp94 deletion in the murine hematopoietic system results in thrombocytopenia, prolonged bleeding time, and giant platelets that are clinically indistinguishable from human BSS. Loss of gp96/grp94 in vivo and in vitro leads to the concomitant reduction in GPIb-IX complex expression due to ER-associated degradation. We further demonstrate that gp96/grp94 binds selectively to the GPIX subunit, but not to gpIbα or gpIbß. Therefore, we identify the platelet GPIX subunit of the GPIb-IX-V complex as an obligate and novel client of gp96/grp94.

An important role of the SRC family kinase Lyn in stimulating platelet granule secretion.

The Src family kinases (SFKs) have been proposed to play stimulatory and inhibitory roles in platelet activation. The mechanisms for these apparently contradictory roles are unclear. Here we show that SFK, mainly Lyn, is important in stimulating a common signaling pathway leading to secretion of platelet granules. Lyn knock-out or an isoform-nonselective SFK inhibitor, PP2, inhibited platelet secretion of both dense and alpha granules and the secretion-dependent platelet aggregation induced by thrombin, collagen, and thromboxane A(2). The inhibitory effect of Lyn knock-out on platelet aggregation was reversed by supplementing granule content ADP, indicating that the primary role of Lyn is to stimulate granule secretion. Inhibitory effect of PP2 on platelet aggregation induced by thrombin and thromboxane A(2) were also reversed by supplementing ADP. Furthermore, PP2 treatment or Lyn knock-out diminished agonist-induced Akt activation and cyclic GMP production. The inhibitory effect of PP2 or Lyn knock-out on platelet response can be corrected by supplementing cyclic GMP. These data indicate that Lyn stimulates platelet secretion by activating the phosphoinositide 3-kinase-Akt-nitric oxide (NO)-cyclic GMP pathway and also provide an explanation why Lyn can both stimulate and inhibit platelet activation.