Platelet Mitochondrial Potential and Function Is Altered During Severe Septic Shock.

Septic shock is a condition characterized by a systemic inflammatory response associated to organ dysfunction. Primary hemostasis is impaired in sepsis, and multiple causative mechanisms have been proposed.

In this study we evaluated platelet function in patients with septic shock. In particular platelet mitochondrial potential was studied as a possible cause of platelet function impairment in septic shock. To test the hypothesis we enrolled 21 consecutive patients admitted to our intensive care unit (ICU) with diagnosis of septic shock. All patients were analysed within 24 hours from admission. 30 ml of citrated blood were withdrawn from each patient and the platelet function tests were performed. Platelet mitochondrial potential (Dy) was assessed by flow cytometry through JC1 staining, espressed as the ratio of FL-1 and FL-2 fluorescence. Platelet aggregation was performed on platelet rich plasma in 5 patients not assuming any drug known to influence platelet function with the following aggregating agents: ADP (final concentration 4 μM), collagen (2 μg/ml), U46619 (10 μM) and TRAP (10 μM). Platelet ATP secretion was quantified and intraplatelet δ-granules content dosage was performed. Expression of GpIb, of GpIIb/IIIa, and of annexin V binding were evaluated by flow cytometry. The study was approved by the Hospital Ethical Committee.

at admission platelet mitochondrial potential was reduced in septic patients in comparison to normal controls (2.6±1.4 vs 3.4±0.3 p=0.06). At day one there was a good correlation between platelet mitochondrial impairment and the Sepsis-related Organ Failure Assessment (SOFA) score, an indicator of sepsis severity (R²=0,39 p<0.001 n=18) with higher values indicating higher degree of severity. Platelets taken from patients with a SOFA score above the group median value (>9, n=8) had Dy values significantly lower than those taken from less severely ill patients (SOFA score ' 9, n=10) and healthy volunteers (1.6±0.6 vs. 3.3±1.4 vs. 3.4±0.3; p<0.01 one way analysis of variance). At day one platelet aggregation was severely impaired, especially with strong aggregating agents as collagen (3/5 of patients with maximum platelet aggregation below 25%). The maximum aggregation caused by collagen seemed to correlate to platelet mitochondrial potential (R²=0,72 n=5 p=0.07). Platelet secretion was equally defective at admission, with pathological secretion to collagen stimulus in 40% of tested patients. Intraplatelet ADP content resulted low in 66% tested (n= 12), while serotonin content was pathological in 58% of patients (n= 12). Platelet GpIIb/IIIa and GpIb expression and annexin V binding were within normal limits.

we demonstrated in a very well selected group of patients that during the early phase of a septic shock a mitochondrial dysfunction occurs, and this may have an impact on platelets dysfunction observed in this condition.

No relevant conflicts of interest to declare.