Vera Pontieri

Platelet-derived exosomes from septic shock patients induce myocardial dysfunction

IntroductionMechanisms underlying inotropic failure in septic shock are incompletely understood. We previously identified the presence of exosomes in the plasma of septic shock patients. These exosomes are released mainly by platelets, produce superoxide, and induce apoptosis in vascular cells by a redox-dependent pathway. We hypothesized that circulating platelet-derived exosomes could contribute to inotropic dysfunction of sepsis.MethodsWe collected blood samples from 55 patients with septic shock and 12 healthy volunteers for exosome separation. Exosomes from septic patients and healthy individuals were investigated concerning their myocardial depressant effect in isolated heart and papillary muscle preparations.ResultsExosomes from the plasma of septic patients significantly decreased positive and negative derivatives of left ventricular pressure in isolated rabbit hearts or developed tension and its first positive derivative in papillary muscles. Exosomes from healthy individuals decreased these variables non-significantly. In hearts from rabbits previously exposed to endotoxin, septic exosomes decreased positive and negative derivatives of ventricular pressure. This negative inotropic effect was fully reversible upon withdrawal of exosomes. Nitric oxide (NO) production from exosomes derived from septic shock patients was demonstrated by fluorescence. Also, there was an increase in myocardial nitrate content after exposure to septic exosomes.ConclusionCirculating platelet-derived exosomes from septic patients induced myocardial dysfunction in isolated heart and papillary muscle preparations, a phenomenon enhanced by previous in vivo exposure to lipopolysaccharide. The generation of NO by septic exosomes and the increased myocardial nitrate content after incubation with exosomes from septic patients suggest an NO-dependent mechanism that may contribute to myocardial dysfunction of sepsis.

Local and systemic effects of hypertonic solution (NaCl 7.5%) in experimental acute pancreatitis.

Objectives: Severe acute pancreatitis (AP) is characterized by hemodynamic alterations and a systemic inflammatory response, leading to a high mortality rate. Treatment of hemorrhagic shock with hypertonic saline solutions significantly reduces mortality through an improvement in the hemodynamic conditions and possibly by an anti-inflammatory effect. Therefore, hypertonic solutions could be effective in AP. Methods: Wistar rats were divided in 4 groups: group C, control, without AP; group NT, AP, without treatment; group NS, treatment with normal saline solution (NaCl 0.9%) 1 hour after AP; group HTS, treatment with hypertonic saline solution (NaCl 7.5%) 1 hour after AP. AP was induced by injection of 2.5% sodium taurocholate into the pancreatic duct. Mean arterial blood pressure (MAP) and heart rate were recorded at 0 and 2, 4, 24, and 48 hours after AP. After induction of AP, animals were killed at 2, 12, 24, and 48 hours for serum amylase, interleukin (IL)-6, and IL-10 analysis, pancreatic tissue culture and histologic analysis, oxidation and phosphorylation of liver mitochondria, pulmonary myeloperoxidase activity (MPO), and mortality study. Results: In animals of groups NS and NT, a significant decrease of MAP was observed 48 hours after AP (NS: 91 ± 3 mm Hg; NT: 89 ± 3 mm Hg) compared with baseline (C: 105 ± 2 mm Hg) and to HTS group (HTS: 102 ± 2 mm Hg; P < 0.05). In animals of group NT, NS, and HTS, serum IL-6 and IL-10 levels were significantly higher at 2 hours after AP compared with the control group. However, IL-6 levels at 12 hours after AP and IL-10 levels at 2 and 12 hours after AP were significant lower in group HTS compared with NS and NT groups (P < 0.05). In group HTS, a decrease of pulmonary MPO activity and of pancreatic infection was observed 24 hours after AP compared with NT and NS groups (P < 0.05). A significant reduction on pancreatic acinar necrosis and mitochondrial dysfunction was observed after 48 hours of AP in animals of group HTS compared with groups NT and NS (P < 0.05). A significant reduction on mortality was observed in HTS (0/14) compared with NS (6/17; 35%) and NT (7/20; 35%). Conclusions: The administration of hypertonic saline solution in experimental AP attenuated hemodynamic alterations, decreased inflammatory cytokines, diminished systemic lesions and pancreatic acinar necrosis, prevented pancreatic infection, and reduced the mortality rate.

Treatment of hemorrhagic shock with hypertonic saline solution modulates the inflammatory response to live bacteria in lungs

Shock and resuscitation render patients more susceptible to acute lung injury due to an exacerbated immune response to subsequent inflammatory stimuli. To study the role of innate immunity in this situation, we investigated acute lung injury in an experimental model of ischemia-reperfusion (I-R) followed by an early challenge with live bacteria. Conscious rats (N = 8 in each group) were submitted to controlled hemorrhage and resuscitated with isotonic saline (SS, 0.9% NaCl) or hypertonic saline (HS, 7.5% NaCl) solution, followed by intratracheal or intraperitoneal inoculation of Escherichia coli. After infection, toll-like receptor (TLR) 2 and 4 mRNA expression was monitored by RT-PCR in infected tissues. Plasma levels of tumor necrosis factor alpha and interleukins 6 and 10 were determined by ELISA. All animals showed similar hemodynamic variables, with mean arterial pressure decreasing to nearly 40 mmHg after bleeding. HS or SS used as resuscitation fluid yielded equal hemodynamic results. Intratracheal E. coli inoculation per se induced a marked neutrophil infiltration in septa and inside the alveoli, while intraperitoneal inoculation-associated neutrophils and edema were restricted to the interseptal space. Previous I-R enhanced lung neutrophil infiltration upon bacterial challenge when SS was used as reperfusion fluid, whereas neutrophil influx was unchanged in HS-treated animals. No difference in TLR expression or cytokine secretion was detected between groups receiving HS or SS. We conclude that HS is effective in reducing the early inflammatory response to infection after I-R, and that this phenomenon is achieved by modulation of factors other than expression of innate immunity components.