Effects of non-surgical periodontal treatment on the L-arginine-nitric oxide pathway and oxidative status in platelets

Several studies have suggested an increase of cardiovascular disease (CVD) risk on periodontitis patients. An enhancement has been demonstrated on both platelet activation and oxidative stress on periodontitis patients, which may contribute for this association. Therefore, the aim of this study was to evaluate the effects of non-surgical periodontal treatment on the l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway and oxidative status in platelets. A total of eight periodontitis patients and eight controls were included in this study. Clinical, laboratory and experimental evaluations were performed on baseline and 90 days after periodontal treatment (except for western blot analysis). The clinical periodontal evaluation included measurements of probing pocket depth (PPD), clinical attachment loss (CAL), % of sites with plaque and % of sites with bleeding on probing. We evaluated: l-[(3)H]arginine influx; nitric oxide synthase (NOS) and arginase enzymes activity and expression; expression of guanylate cyclase and phosphodiesterase-5 enzymes; cGMP levels; platelet aggregation; oxidative status through superoxide dismutase (SOD) and catalase activities, and measurement of reactive oxygen species (ROS) levels and C-reactive protein (CRP) levels. The initial results showed an activation of both l-arginine influx and via system y (+ )L associated with reduced intraplatelet cGMP levels in periodontitis patients and increased systemic levels of CRP. After periodontal treatment, there was a significant reduction of the % of sites with PPD 4-5mm, % of sites with CAL 4-5 mm, and an enhancement in cGMP levels and SOD activity. Moreover, CRP levels were reduced after treatment. Therefore, alterations in the intraplatelet l-arginine-NO-cGMP pathway and oxidant-antioxidant balance associated with a systemic inflammatory response may lead to platelet dysfunction, which may contribute to a higher risk of CVD in periodontitis.

Low plasma levels of L-arginine, impaired intraplatelet nitric oxide and platelet hyperaggregability: implications for cardiovascular disease in depressive patients

BACKGROUND

Major depression (MD) is an independent cardiovascular risk factor, but the exact mechanisms are not clear. In this study we have investigated the intraplatelet L-arginine-nitric oxide (NO) pathway and platelet function in depressive patients.

METHODS

Nineteen unmedicated patients with MD (34±4years) and 19 control subjects (CS, 34±3years) were included. L-[(3)H]-arginine influx, NO synthase (NOS) activity and intracellular cGMP levels were evaluated in platelets, as well as the expression of eNOS, iNOS, arginase and soluble guanylate cyclase (sGC), platelet aggregation and the systemic amino acid profile in MD patients and CS.

RESULTS

L-arginine influx (pmol/10(9)cells/min) in platelets was reduced from 46.2±9.5 to 20.02±2.12 in depression. NOS activity (pmol/10(8) cells) was diminished in MD patients (0.09±0.01) compared to CS (0.17±0.01). Intracellular cGMP levels were also impaired in MD patients associated with hyperaggregability. Moreover, the concentration of plasma L-arginine was reduced by 20% in MD patients. The expression of eNOS, iNOS, arginase II and sGC in platelet lysates was not affected by MD.

LIMITATIONS

Small number of patients in the study.

CONCLUSIONS

This study has demonstrated an impairment of L-arginine-NO signaling in platelets from MD patients, suggesting a role in platelet activation and cardiovascular events.

Increased nitric oxide production in platelets from severe chronic renal failure patients

Nitric oxide (NO) production occurs through oxidation of the amino acid L-arginine by NO synthase (NOS). NO inhibits platelet activation by increasing the levels of cyclic guanosine monophosphate (cGMP), thus maintaining vascular homeostasis. Our group previously demonstrated (da Silva et al. 2005) an enhancement of the L-arginine-NO-cGMP pathway in platelets taken from chronic renal failure (CRF) patients on haemodialysis associated with reduced platelet aggregation. We investigate the platelet L-arginine-NO-cGMP pathway, platelet function, and inflammation from patients in CRF on conservative treatment. A total of 42 CRF patients and 42 controls (creatinine clearance = 27 ± 3 vs. 93 ± 1 mL per min per 1.73 m2, respectively) participated in this study. NOS activity and expression and cGMP concentration were measured in platelets. Platelet aggregation induced by collagen or ADP was evaluated and plasma levels of fibrinogen were determined by the Clauss method. A marked increase in basal NOS activity was seen in undialysed CRF patients compared with controls, accompanied by an elevation of fibrinogen plasma levels. There were no differences in expression of NOS and in cGMP levels. In this context, platelet aggregation was not affected. We provide the first evidence of increased intraplatelet NO biosynthesis in undialysed CRF patients, which can be an early marker of future haemostatic abnormalities during dialysis treatment.

Insulin resistance in obesity and metabolic syndrome: is there a connection with platelet l-arginine transport?

OBJECTIVE

Nitric oxide (NO) is a short-lived gaseous messenger with multiple physiological functions including regulation of blood flow, platelet adhesion and aggregation inhibition. NO synthases (NOS) catalyze the conversion of cationic amino acid L-arginine in L-citrulline and NO. Despite an increasing prevalence of obesity and metabolic syndrome (MetS) in the last decades, the exact mechanisms involved in the pathogenesis and cardiovascular complications are not fully understood. We have examined the effects of obesity and MetS on the L-arginine-NO-cGMP pathway in platelets from a population of adolescents.

MATERIALS

A total of twenty six adolescent patients (13 with obesity and 13 with MetS) and healthy volunteers (n=14) participated in this study. Transport of L-arginine, NO synthase (NOS) activity and cGMP content in platelets were analyzed. Moreover, platelet function, plasma levels of L-arginine, metabolic and clinical markers were investigated in these patients and controls.

RESULTS

L-arginine transport (pmol/10(9) cells/min) in platelets via system y(+)L was diminished in obese subjects (20.8±4.7, n=10) and MetS patients (18.4±3.8, n=10) compared to controls (52.3±14.8, n=10). The y(+)L transport system correlated negatively to insulin levels and Homeostasis Model Assessment of Insulin Resistance (HOMA IR) index. No differences in NOS activity and cGMP content were found among the groups. Moreover, plasma levels of L-arginine were not affected by obesity or MetS.

DISCUSSION

Our study provides the first evidence that obesity and MetS lead to a dysfunction of L-arginine influx, which negatively correlates to insulin resistance. These findings could be a premature marker of future cardiovascular complications during adulthood.

Oxidative stress, l-arginine-nitric oxide and arginase pathways in platelets from adolescents with anorexia nervosa

Anorexia nervosa (AN) is associated with high cardiovascular mortality. Nitric oxide (NO) inhibits platelet function and regulates the cardiovascular homeostasis. The aim of this study was to investigate the l-arginine-NO-GMPc and arginase pathways and oxidative stress in platelets from patients with AN. Intraplatelet l-arginine transport, NOS expression and activity, cGMP levels, platelet aggregation, arginase expression and oxidative stress were measured in adolescent patients with AN (n=11) and healthy controls (n=12). Plasma l-arginine levels were significantly reduced in AN. l-arginine transport, NOS activity and cGMP basal levels were reduced in platelets associated with unchanged platelet aggregability. The expression of NOS isoforms was not affected. TBARS production was diminished, while the activity of superoxide dismutase was elevated in AN patients. There was an overexpression of arginase II in AN. Alterations of l-arginine-NO-GMPc and arginase pathways in platelets can be early predictors of the incidence of cardiovascular disease into adult life in AN.

Update information on drug metabolism systems--2009, part II: summary of information on the effects of diseases and environmental factors on human cytochrome P450 (CYP) enzymes and transporters

The present paper is an update of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 (CYP) enzymes and transporters. The data are presented in tabular form (Tables 1 and 2) and are a continuation of previously published summaries on the effects of drugs and other chemicals on CYP enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29(1-2), 413-580., Rendic, S. Drug Metab. Rev., 2002, 34(1-2), 83-448.). The collected information presented here is as stated by the cited author(s), and in cases when several references are cited the latest published information is included. Inconsistent results and conclusions obtained by different authors are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file, for information about file availability contact the corresponding author.

Dengue fever activates the L-arginine-nitric oxide pathway: an explanation for reduced aggregation of human platelets

In patients with Dengue fever, a viral inflammatory syndrome, haemorrhage is a significant pathological feature, yet the underlying mechanisms remain unclear. Nitric oxide (NO) is an important regulator of platelet function, inhibiting aggregation, recruitment and adhesion to the vascular endothelium. We have investigated whether changes in the activity of the L-arginine-NO pathway in human platelets may account for increased bleeding in patients with Dengue fever. A total of 16 patients with Dengue fever and 18 age-matched healthy volunteers participated in the study. Collagen induced platelet aggregation in a dose-dependent manner in both Dengue patients and controls, but the degree of platelet aggregation was significantly reduced in the patient group. Elevated rates of L-arginine transport in Dengue fever patients were associated with enhanced NO synthase activity and elevated plasma fibrinogen levels. The present study provides the first evidence that Dengue fever is associated with increased L-arginine transport and NO generation and reduced platelet aggregation.