This report describes a potent and selective inhibitor of multidrug and toxin extrusion (MATE) protein, pyrimethamine (PYR), and examines its effect on the urinary and biliary excretion of typical Mate1 substrates in mice. In vitro inhibition studies demonstrated that PYR is a potent inhibitor of mouse (m)Mate1 (K_i = 145 nM) among renal organic cation transporters mOctn1 and mOctn2 (K_i > 30 μM), mOct1 (K_i = 3.6 μM), and mOct2 (K_i = 6.0 μM). PYR inhibited the uptake of metformin by kidney brush-border membrane vesicles (BBMVs) (K_i = 41 nM) and canalicular membrane vesicles in the presence of outward gradient of H⁺. PYR treatment significantly increased the kidney-to-plasma ratio of tetraethylammonium, and both the liver- and kidney-to-plasma ratios of metformin in mice, whereas it did not affect their plasma concentrations and urinary excretion rates. Furthermore, the plasma lactate concentration, a biomarker for inhibition of gluconeogenesis by metformin, was significantly higher in the PYR-treated group than in the control group. These results not only suggest the importance of mMate1 in the efflux of organic cations into the urine and bile in mice but also the importance of canalicular efflux mediated by MATE proteins for the therapeutic efficacy of metformin. PYR is a potent inhibitor of human (h)MATE1 and hMATE2-K (K_i = 77 and 46 nM, respectively) and H⁺ and organic cation exchanger in human kidney BBMVs (K_i = 31 nM) in the presence of outward gradient of H⁺. Taken together, PYR can be used as a potent probe inhibitor of human MATE transporters.

LETM1 is a mitochondrial inner membrane protein that is required for maintaining the mitochondrial morphology and cristae structures, and regulates mitochondrial ion homeostasis. Here we report a role of LETM1 in the organization of cristae structures. We identified four amino acid residues of human LETM1 that are crucial for complementation of the growth deficiency caused by gene deletion of a yeast LETM1 orthologue. Substituting amino acid residues with alanine disrupts the correct assembly of a protein complex containing LETM1 and prevents changes in the mitochondrial morphology induced by exogenous LETM1 expression. Moreover, the LETM1 protein changes the shapes of the membranes of in vitro-reconstituted proteoliposomes, leading to the formation of invaginated membrane structures on artificial liposomes. LETM1 mutant proteins with alanine substitutions fail to facilitate the formation of invaginated membrane structures, suggesting that LETM1 plays a fundamental role in the organization of mitochondrial membrane morphology.

Dengue fever during pregnancy is an expanding issue in Southeast Asia; however, the knowledge of adverse effects on mothers and neonates remains limited. Therefore, we aimed to determine the impact of dengue fever. The clinical information of 20 patients of dengue fever during pregnancy in Vietnam from January 1, 2015 to December 31, 2015 was collected and their outcomes were retrospectively investigated. A total of 18 patients (90%) presented with positivity of nonstructural protein 1, and a primary infection. Additionally, 4 patients (20%) had preterm deliveries and 1 (5%) had a stillborn child. All live-born neonates were discharged from the hospital uneventfully. Also, 6 patients (30%) required platelet transfusion and 3 of them received transfusion before delivery, but there were no maternal death. In addition, 3 cases of patients (15%) developed to postpartum hemorrhage (PPH), and their platelet concentrations were significantly lower than those of patients without PPH [90.0 (19.0 - 374.0) × 103 vs. 40.0 (12.0 - 57.0) × 103 cell/μl, p = 0.001]. In addition, patients with PPH also presented with elevated liver enzymes. Pregnant patients with low platelet counts should be recognized as being at high risk for PPH.

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