Parasite histones are toxic to brain endothelium and link blood barrier breakdown and thrombosis in cerebral malaria

Microvascular thrombosis and blood–brain barrier (BBB) breakdown are key components of cerebral malaria (CM) pathogenesis in African children and are implicated in fatal brain swelling. How Plasmodium falciparum infection causes this endothelial disruption and why this occurs, particularly in the brain, is not fully understood. In this study, we have demonstrated that circulating extracellular histones, equally of host and parasite origin, are significantly elevated in CM patients. Higher histone levels are associated with brain swelling on magnetic resonance imaging. On postmortem brain sections of CM patients, we found that histones are colocalized with P falciparum–infected erythrocytes sequestered inside small blood vessels, suggesting that histones might be expelled locally during parasite schizont rupture. Histone staining on the luminal vascular surface colocalized with thrombosis and leakage, indicating a possible link between endothelial surface accumulation of histones and coagulation activation and BBB breakdown. Supporting this, patient sera or purified P falciparum histones caused disruption of barrier function and were toxic to cultured human brain endothelial cells, which were abrogated with antihistone antibody and nonanticoagulant heparin. Overall, our data support a role for histones of parasite and host origin in thrombosis, BBB breakdown, and brain swelling in CM, processes implicated in the causal pathway to death. Neutralizing histones with agents such as nonanticoagulant heparin warrant exploration to prevent brain swelling in the development or progression of CM and thereby to improve outcomes.

Extracellular Histones Play an Inflammatory Role in Acid Aspiration-induced Acute Respiratory Distress Syndrome

Background: Systemic inflammation is a key feature in acid aspiration-induced acute respiratory distress syndrome (ARDS), but the factors that trigger inflammation are unclear. The authors hypothesize that extracellular histones, a newly identified inflammatory mediator, play important roles in the pathogenesis of ARDS. Methods: The authors used a hydrochloric acid aspiration-induced ARDS model to investigate whether extracellular histones are pathogenic and whether targeting histones are protective. Exogenous histones and antihistone antibody were administered to mice. Heparin can bind to histones, so the authors studied whether heparin could protect from ARDS using cell and mouse models. Furthermore, the authors analyzed whether extracellular histones are clinically involved in ARDS patients caused by gastric aspiration. Results: Extracellular histones in bronchoalveolar lavage fluid of acid-treated mice were significantly higher (1.832 ± 0.698) at 3 h after injury than in sham-treated group (0.63 ± 0.153; P = 0.0252, n = 5 per group). Elevated histones may originate from damaged lung cells and neutrophil infiltration. Exogenous histones aggravated lung injury, whereas antihistone antibody markedly attenuated the intensity of ARDS. Notably, heparin provided a similar protective effect against ARDS. Analysis of plasma from ARDS patients (n = 21) showed elevated histones were significantly correlated with the degree of ARDS and were higher in nonsurvivors (2.723 ± 0.2933, n = 7) than in survivors (1.725 ± 0.1787, P = 0.006, n = 14). Conclusion: Extracellular histones may play a contributory role toward ARDS by promoting tissue damage and systemic inflammation and may become a novel marker reflecting disease activity. Targeting histones by neutralizing antibody or heparin shows potent protective effects, suggesting a potentially therapeutic strategy.

Propylthiouracil-induced lupus-like or vasculitis syndrome

A 27 year old female with Graves’ disease presented with fever, exertional dyspnea and polyarthralgia. Erythema nodosum had occured three months earlier. The patient declared irregular use of propylthiouracil (PTU) for the last 8 months. Neutropenia and microscopic hematuria developed in the second week of admission. Chest X-ray showed inhomogenous pulmonary opacities, left pleural effusion and cardiomegaly. Computed tomography (CT) revealed multiple subpleural nodules, left pleural effusion, pericardial effusion, enlarged mediastinal and axillary lymph nodes. Bronchoalveolar lavage (BAL) cytology demonstrated hemosiderin laden macrophages. Histopathologic examination of the transbronchial biopsy specimen revealed a nonspecific inflammation. Serum was positive for ANA, P-ANCA, MPO-ANCA, PR3-ANCA and negative for anti-ds-DNA, C-ANCA, C3, C4 and antihistone antibody. All symptoms resolved in two months after PTU withdrawal and starting steroid treatment. The same clinical manifestations recurred when the patient used PTU erronously one month after discharge. This is a case of PTU induced-autoimmune disease in whom the accurate distinction between drug-induced-lupus (DIL) and vasculitis was not possible due to the significant overlap of clinical and laboratory findings causing a significant diagnostic challenge for the chest physician.

Subacute Cutaneous Lupus Erythematosus Induced by Nifedipine

Background: Subacute cutaneous lupus erythematosus (SCLE) has been reported to be associated with the use of several drugs, including thiazides, terbinafine, and, rarely, calcium channel blockers. Objective: A case of SCLE induced by nifedipine is presented. Methods and Results: A 48-year-old white woman developed a papulosquamous and annular eruption in sun-exposed areas during the summer. The patient was taking nifedipine for essential hypertension for four years. Serology showed the presence of antinuclear and anti-Ro/SSA as well as antihistone antibodies. Histopathologic and immunopathologic (granular IgM deposits at the dermoepidermal junction) findings confirmed the diagnosis of SCLE. Nifedipine discontinuation led to rapid improvement with almost complete resolution of skin lesions in one month in the absence of active treatment. Reduction of antinuclear, anti-Ro/SSA, and antihistone antibody levels was documented after six months. Conclusion: Nifedipine can cause SCLE after a long period of administration. Antihistone antibodies may be associated with drug-induced SCLE.