Shiga toxin (Stx)-producing E.coli O157:H7 has become a global threat to public health; it is a primary cause of diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure with thrombi occluding renal microcirculation. In this study, we explored whether Stx triggers complement-dependent microvascular thrombosis in in vitro and in vivo experimental settings of HUS. Stx induced on human microvascular endothelial cell surface the expression of P-selectin, which bound and activated C3 via the alternative pathway, leading to thrombus formation under flow. In the search for mechanisms linking complement activation and thrombosis, we found that exuberant complement activation in response to Stx generated an increased amount of C3a that caused further endothelial P-selectin expression, thrombomodulin (TM) loss, and thrombus formation. In a murine model of HUS obtained by coinjection of Stx2 and LPS and characterized by thrombocytopenia and renal dysfunction, upregulation of glomerular endothelial P-selectin was associated with C3 and fibrin(ogen) deposits, platelet clumps, and reduced TM expression. Treatment with anti–P-selectin Ab limited glomerular C3 accumulation. Factor B-deficient mice after Stx2/LPS exhibited less thrombocytopenia and were protected against glomerular abnormalities and renal function impairment, indicating the involvement of complement activation via the alternative pathway in the glomerular thrombotic process in HUS mice. The functional role of C3a was documented by data showing that glomerular fibrin(ogen), platelet clumps, and TM loss were markedly decreased in HUS mice receiving C3aR antagonist. These results identify Stx-induced complement activation, via P-selectin, as a key mechanism of C3a-dependent microvascular thrombosis in diarrhea-associated HUS.

Background Patients with cancer are considered highly vulnerable to the recent coronavirus disease 2019 (COVID‐19) pandemic. However, there are still few data on COVID‐19 occurring in hematologic patients. Methods One hundred two patients with COVID‐19 symptoms and a nasopharyngeal swab positive for severe acute respiratory syndrome coronavirus 2 seen at 2 hematologic departments located in Lombardy, Italy, during March 2020 were studied. Risk factors for acquiring COVID‐19 were analyzed by comparisons of patients with COVID‐19 and the standard hematologic population managed at the same institutions in 2019. Thirty‐day survival was compared with the survival of matched uninfected control patients with similar hematologic disorders and nonhematologic patients affected by COVID‐19. Results Male sex was significantly more prevalent in patients with COVID‐19. The infection occurred across all different types of hematologic disease; however, the risk of acquiring a COVID‐19 infection was lower for patients with chronic myeloproliferative neoplasms, including chronic myeloid leukemia, and higher for patients with immune‐mediated anemia on immunosuppressive‐related treatments. The 30‐day mortality rate was 39.2%, which was higher than the rates for nonhematologic patients with COVID‐19 (23.5%; P = .02) and uninfected hematologic controls (3%; P < .001). The severity of the respiratory syndrome at presentation and active hematologic treatment were independently associated with a worse prognosis. Neither diagnosis nor disease status affected the prognosis. The worst prognosis was demonstrated among patients on active hematologic treatment and those with more severe respiratory syndrome at COVID‐19 presentation. Conclusions During the COVID‐19 pandemic, patients should be advised to seek medical attention at the earliest signs of dyspnea and/or respiratory infection. Physicians should perform a risk‐benefit analysis to determine the impact of temporarily deferring nonlifesaving treatments versus the risk of adverse outcomes associated with COVID‐19. Lay Summary Coronavirus disease 2019 (COVID‐19) infection occurs across all different types of hematologic disease; however, the risk of acquiring it is lower for patients with chronic myeloproliferative neoplasms, including chronic myeloid leukemia, and higher for patients with immune‐mediated anemia on immunosuppressive treatment. The 30‐day mortality rate is 39.2%, which is far higher than the rates for both uninfected hematologic controls (3%; P < .001) and nonhematologic patients with COVID‐19 (23.5%; P = .02) despite matching for age, sex, comorbidities, and severity of disease. Variables independently associated with a worse prognosis are the severity of the respiratory syndrome at presentation and any type of active hematologic treatment. Neither diagnosis nor disease status influence the prognosis.

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Pseudomonas aeruginosa is a well-known cause of severe and potentially life-threatening infections among hematological patients. A prospective epidemiological surveillance program ongoing at our Hematology Unit revealed an increase over time of P. aeruginosa bloodstream infections (BSI). Their impact on outcome and antibiotic susceptibility was analyzed. BSI which consecutively occurred at our institution during a 70-month period were evaluated and correlated with type of pathogen, status of underlying disease, neutropenia, previous antibiotic therapy, resistance to antibiotics, and outcome. During the observation period, 441 BSI were recorded. Frequency of Gram-negative BSI was higher than that of other pathogens (57.3%). Overall, 66 P. aeruginosa BSI were recorded; 22 out of 66 were multiresistant (MR P. aeruginosa). Thirty-day mortality for all BSI was 11.3%; it was 27.3% for P. aeruginosa BSI and 36.4% for MR P. aeruginosa. At multivariate analysis, only active hematological disease and P. aeruginosa BSI were associated to an increased risk of death. For MR P. aeruginosa, BSI mortality was 83.3% vs. 18.8% when empiric therapy included or not an antibiotic with in vitro activity against P. aeruginosa (p=0.011). Together with active disease, the emergence of P. aeruginosa BSI, particularly if multiresistant, was responsible for an increased risk of death among hematological patients at our institution. In this scenario, reconsidering the type of combination antibiotic therapy to be used as empiric treatment of neutropenic fever was worthwhile.

Diabetic nephropathy is associated with cardiovascular morbidity. Angiotensin-converting enzyme (ACE) inhibitors provide imperfect renoprotection in advanced type 2 diabetes, and cardiovascular risk remains elevated. Endothelin (ET)-1 has a role in renal and cardiac dysfunction in diabetes. Here, we assessed whether combination therapy with an ACE inhibitor and ET(A) receptor antagonist provided reno- and cardioprotection in rats with overt type 2 diabetes. Four groups of Zucker diabetic fatty (ZDF) rats were treated orally from 4 (when proteinuric) to 8 mo with vehicle, ramipril (1 mg/kg), sitaxsentan (60 mg/kg), and ramipril plus sitaxsentan. Lean rats served as controls. Combined therapy ameliorated proteinuria and glomerulosclerosis mostly as a result of the action of ramipril. Simultaneous blockade of ANG II and ET-1 pathways normalized renal monocyte chemoattractant protein-1 and interstitial inflammation. Cardiomyocyte loss, volume enlargement, and capillary rarefaction were prominent abnormalities of ZDF myocardium. Myocyte volume was reduced by ramipril and sitaxsentan, which also ameliorated heart capillary density. Drug combination restored myocardial structure and reestablished an adequate capillary network in the presence of increased cardiac expression of VEGF/VEGFR-1, and significant reduction of oxidative stress. In conclusion, in type 2 diabetes concomitant blockade of ANG II synthesis and ET-1 biological activity through an ET(A) receptor antagonist led to substantial albeit not complete renoprotection, almost due to the ACE inhibitor. The drug combination also showed cardioprotective properties, which however, were mainly dependent on the contribution of the ET(A) receptor antagonist through the action of VEGF.