Frequency of mitochondrial defects in patients with chronic intestinal pseudo-obstruction.

BACKGROUND & AIMS: Chronic intestinal pseudo-obstruction (CIPO) is a rare disorder caused by intestinal dysmotility and characterized by chronic symptoms suggesting bowel obstruction in the absence of fixed, occluding lesions. CIPO has been associated with primary defects of the mitochondrial oxidative phosphorylation pathway, although the frequency of mitochondrial disorders in patients with CIPO is unknown. This study evaluates mitochondrial function in patients with CIPO. METHODS: A retrospective study was performed of data collected from 80 CIPO patients at a tertiary centre over a 25-year period. Mitochondrial disorders were detected by analysis of serum lactate and thymidine phosphorylase activities, brain magnetic resonance images, and muscle biopsies. Genes encoding thymidine phosphorylase, mitochondrial DNA tRNA(leu(UUR)) or tRNA(lys), and DNA polymerase-gamma were analyzed for mutations. RESULTS: Mitochondrial defects were identified in 15 patients (10 women; median age at diagnosis 32 years), representing 19% of the study cohort. All 15 patients had extra-digestive symptoms, 5 had mutations in the thymidine phosphorylase gene, 2 had mutations in tRNA(leu(UUR)), and 5 had mutations in the DNA polymerase-gamma gene. No genetic defect was detected in 3 of the patients with mitochondrial disorders. Patients with mitochondrial CIPO differed from patients without mitochondrial defects in their very severe nutritional status (frequent and long-term requirement for parenteral nutrition) and poor prognosis (frequent digestive and neurologic complications that led to a high incidence of premature death). CONCLUSION: Mitochondrial disorders seem to be an important cause of CIPO. Patients with CIPO, especially severe cases with associated neurologic symptoms, should be tested for mitochondrial defects.

Surface area loss and increased sphericity account for the splenic entrapment of subpopulations of Plasmodium falciparum ring-infected erythrocytes.

Ex vivo perfusion of human spleens revealed innate retention of numerous cultured Plasmodium falciparum ring-infected red blood cells (ring-iRBCs). Ring-iRBC retention was confirmed by a microsphiltration device, a microbead-based technology that mimics the mechanical filtering function of the human spleen. However, the cellular alterations underpinning this retention remain unclear. Here, we use ImageStream technology to analyze infected RBCs' morphology and cell dimensions before and after fractionation with microsphiltration. Compared to fresh normal RBCs, the mean cell membrane surface area loss of trophozoite-iRBCs, ring-iRBCs and uninfected co-cultured RBCs (uRBCs) was 14.2% (range: 8.3-21.9%), 9.6% (7.3-12.2%) and 3.7% (0-8.4), respectively. Microsphilters retained 100%, ∼50% and 4% of trophozoite-iRBCs, ring-iRBCs and uRBCs, respectively. Retained ring-iRBCs display reduced surface area values (estimated mean, range: 17%, 15-18%), similar to the previously shown threshold of surface-deficient RBCs retention in the human spleen (surface area loss: >18%). By contrast, ring-iRBCs that successfully traversed microsphilters had minimal surface area loss and normal sphericity, suggesting that these parameters are determinants of their retention. To confirm this hypothesis, fresh normal RBCs were exposed to lysophosphatidylcholine to induce a controlled loss of surface area. This resulted in a dose-dependent retention in microsphilters, with complete retention occurring for RBCs displaying >14% surface area loss. Taken together, these data demonstrate that surface area loss and resultant increased sphericity drive ring-iRBC retention in microsphilters, and contribute to splenic entrapment of a subpopulation of ring-iRBCs. These findings trigger more interest in malaria research fields, including modeling of infection kinetics, estimation of parasite load, and analysis of risk factors for severe clinical forms. The determination of the threshold of splenic retention of ring-iRBCs has significant implications for diagnosis (spleen functionality) and drug treatment (screening of adjuvant therapy targeting ring-iRBCs).