Diabetes mellitus (DM) and hyperglycaemia are associated with platelet activation. The present study was designed to investigate how high glucose levels influence platelet function. Fasting human blood was incubated with different concentrations of D-glucose (5, 15 and 30 mmol/l) and other sugars without or with in vitro stimuli. Platelet activation was monitored by whole blood flow cytometry. High glucose levels enhanced adenosine diphosphate (ADP)- and thrombin receptor-activating peptide (TRAP)-induced platelet P-selectin expression, and TRAP-induced platelet fibrinogen binding. Similar effects were seen with 30 mmol/l L-glucose, sucrose and galactose. Hyperglycaemia also increased TRAP-induced platelet-leucocyte aggregation. Protein kinase C (PKC) blockade did not counteract the enhancement of platelet P-selectin expression, but abolished the enhancement of TRAP-induced platelet fibrinogen binding by hyperglycaemia. Superoxide anion scavenging by superoxide dismutase (SOD) attenuated the hyperglycaemic enhancement of platelet P-selectin expression, but did not counteract the enhancement of TRAP-induced platelet fibrinogen binding. Hyperglycaemia did not alter platelet intracellular calcium responses to agonist stimulation. Blockade of cyclo-oxygenase (COX), phosphotidylinositol-3 (PI3) kinase, or nitric oxide synthase, or the addition of insulin did not influence the effect of hyperglycaemia. In conclusion, high glucose levels enhanced platelet reactivity to agonist stimulation through elevated osmolality. This occurred via superoxide anion production, which enhanced platelet P-selectin expression (secretion), and PKC signalling, which enhanced TRAP-induced fibrinogen binding (aggregablity).

ContextRapid cycling is a severe form of bipolar disorder with an increased rate of episodes that is particularly treatment-responsive to chronotherapy and stable sleep-wake cycles. We hypothesized that the P2RX7 gene would be affected by sleep deprivation and be implicated in rapid cycling.ObjectivesTo assess whether P2RX7 expression is affected by total sleep deprivation and if variation in P2RX7 is associated with rapid cycling in bipolar patients.DesignGene expression analysis in peripheral blood mononuclear cells (PBMCs) from healthy volunteers and case-case and case-control SNP/haplotype association analyses in patients.ParticipantsHealthy volunteers at the sleep research center, University of California, Irvine Medical Center (UCIMC), USA (n = 8) and Swedish outpatients recruited from specialized psychiatric clinics for bipolar disorder, diagnosed with bipolar disorder type 1 (n = 569; rapid cycling: n = 121) and anonymous blood donor controls (n = 1,044).Results P2RX7 RNA levels were significantly increased during sleep deprivation in PBMCs from healthy volunteers (p = 2.3*10−9). The P2RX7 rs2230912 _A allele was more common (OR = 2.2, p = 0.002) and the ACGTTT haplotype in P2RX7 (rs1718119 to rs1621388) containing the protective rs2230912_G allele (OR = 0.45–0.49, p = 0.003–0.005) was less common, among rapid cycling cases compared to non-rapid cycling bipolar patients and blood donor controls.ConclusionsSleep deprivation increased P2RX7 expression in healthy persons and the putatively low-activity P2RX7 rs2230912 allele A variant was associated with rapid cycling in bipolar disorder. This supports earlier findings of P2RX7 associations to affective disorder and is in agreement with that particularly rapid cycling patients have a more vulnerable diurnal system.

Diabetes mellitus is associated with platelet dysfunction, and hypoglycemic treatments may counteract this diabetic alteration. We thus studied how acute hyperglycemia influences platelet function. Fast blood (n=20) was incubated with different levels of glucose (5, 15, and 30 mM) for 5 min, and without or with in vitro stimuli. Platelet activation was monitored by whole blood flow cytometry, while platelet aggregation was also measured using impedance aggregometry. Blood glucose levels had little influence on unstimulated platelets. Hyperglycemia enhanced ADP- and TRAP-induced platelet P-selectin expression. Hyperglycemia also increased TRAP-induced platelet fibrinogen binding. High glucose levels mildly increased ADP- and TRAP-induced platelet-leukocyte aggregation. The blockade of protein kinase C (PKC) slightly attenuated ADP-induced, and markedly inhibited TRAP-induced platelet activation. PKC blockade had, however, little effect on hyperglycemia effect. Platelet P-selectin expression induced by the direct PKC activator phorbol 12-myristate 13-acetate (PMA) was not augmented by hyperglycemia. Superoxide anion scavenging by superoxide dismutase (SOD) reduced, whistle cyclo-oxygenase (COX) inhibition by naproxen did not reduced the enhancing effect of platelet activation by hyperglycemia. In conclusion, acute hyperglycemia enhances platelet activation in whole blood. Superoxide anions contribute importantly to hyperglycemia-enhanced platelet activation, while other mechanisms not identified presently also contribute to hyperglycemic effects.

Introduction: Rapid cycling (RC) is a severe form of bipolar disorder (BD) with an increased rate of episodes. Circadian disturbances are common in BD, and those with RC might be even more vulnerable. Aims: To investigate if the P2RX7 gene would be involved in the circadian rhythm and in part thereby be implicated in RC. Methods: Gene expression was analyzed in peripheral mononuclear cells (PBMCs) from healthy volunteers (n=8) at the sleep research center, University of California, Irvine Medical Center, USA. Swedish outpatients recruited from psychiatric clinics for BD, diagnosed with BD type 1(n=569; RC: n=121) and anonymous blood donor controls (n=1,044) was investigated in case-case and case-control SNP/haplotype association analyses. Results: P2RX7 RNA levels were dramatically increased during sleep deprivation in PBMCs from the healthy volunteers (p=2.3*10-9). The P2RX7 rs 2230912 _A allele was more common (OR=2.2, p=0.002) and the ACGTTT haplotype in P2RX7 containing the protective rs2230912_G allele was less common, among RC cases compared to nonRC bipolar patients and blood donor controls. Conclusions: Sleep deprivation activates P2RX7 expression in healthy persons which suggests that P2RX7 is involved in, or downstream, circadian rhythm regulation. The putatively low-activity P2RX7 rs2230912 allele A variant was associated with RC in BD which supports earlier findings of P2RX7 associations to affective disorder.