G. Beattie1, C. Cohan1, W. Brigode1, E. J. Miraflor1, G. P. Victorino1 1University Of California San Francisco – East Bay,Department Of Surgery,Oakland, CA, USA
Introduction: Phosphatidylserine (PS) is usually an intracellularly oriented membrane phospholipid. Externalized PS on activated or apoptotic cells is a signal for phagocytosis. In sepsis, persistent PS exposure is a signal for activation of the coagulation and inflammatory cascades. As such, PS may be a key molecule in sepsis induced cellular and organ injury. We hypothesize that PS blockade provides a protective effect in sepsis induced organ dysfunction.
Methods: Anesthetized adult female Sprague-Dawley rats were allocated to control (n=5), sepsis (n=6), or sepsis + PS blockade (n=9) groups. Each group underwent 4-hour intravenous infusion protocols as follows: sepsis was induced using 0.65mg/h of lipopolysaccharide (LPS), PS blockade was performed using diannexin 400mcg/kg dosed at time zero and at two hours, and controls were infused with lactated ringers. Gut dysfunction was evaluated using intravital microscopy to measure microvascular leak (Lp). Lung and renal dysfunction were evaluated by arterial blood gas (ABG) and serum creatinine (Cr) analysis, respectively. Activated clotting time (ACT) and glomerular fibrin deposition measurements were performed to evaluate coagulopathy. Lp units are listed as x10-7 cm*s-1*cmH2O-1. Data are presented as mean ± standard error of the mean. Statistical analysis was performed with paired t-test and analysis of variance.
Results: In the sepsis group, Lp increased 2-fold from 1.17± 0.03 to 2.62 ± 0.20 (p< 0.01). In the sepsis + PS blockade group, Lp increased over the first two hours of infusion (from 1.16 ± 0.01 to 1.48 ± 0.01), however, unlike the sepsis group, Lp returned to baseline levels at four hours (p < 0.01). Lp in the control group remained unchanged. There was no difference in pulmonary dysfunction in any of the groups (p=0.6). Renal function worsened in the sepsis group with a 59% increase in Cr from 0.53 to 0.88 mg/dL (p=0.01). In the sepsis + PS blockade group, there was a trend toward attenuation of renal dysfunction as Cr levels only increased 40%, from 0.5 to 0.70mg/dL, compared to the sepsis group (p=0.1). Creatinine levels remained stable in the control group. Coagulopathy was observed in the sepsis group as ACT increased 19% (p =0.04) and glomerular fibrin deposition increased compared to controls, (99.5% ± 0.5% glomeruli involvement vs 20% ± 4.6%, p<0.001). There was a protective effect of PS blockade in sepsis as ACT decreased 8% (p=0.03) and glomerular fibrin deposition improved from 99.5% ± 0.5% glomeruli involvement in sepsis alone to 20% ± 9.8% with PS blockade in sepsis (p=0.008).
Conclusion: In sepsis, PS blockade had a protective effect on gut dysfunction and coagulopathy with a trend toward improved renal function. Increased PS exposure during cellular injury may be a key mediator of organ dysfunction and coagulopathy during sepsis. This may provide insights into novel treatment options for septic patients.