Plasmodium falciparum: differential selection of drug resistance alleles in contiguous urban and peri-urban areas of Brazzaville, Republic of Congo

The African continent is currently experiencing rapid population growth, with rising urbanization increasing the percentage of the population living in large towns and cities. We studied the impact of the degree of urbanization on the population genetics of Plasmodium falciparum in urban and peri-urban areas in and around the city of Brazzaville, Republic of Congo. This field setting, which incorporates local health centers situated in areas of varying urbanization, is of interest as it allows the characterization of malaria parasites from areas where the human, parasite, and mosquito populations are shared, but where differences in the degree of urbanization (leading to dramatic differences in transmission intensity) cause the pattern of malaria transmission to differ greatly. We have investigated how these differences in transmission intensity affect parasite genetic diversity, including the amount of genetic polymorphism in each area, the degree of linkage disequilibrium within the populations, and the prevalence and frequency of drug resistance markers. To determine parasite population structure, heterozygosity and linkage disequilibrium, we typed eight microsatellite markers and performed haplotype analysis of the msp1 gene by PCR. Mutations known to be associated with resistance to the antimalarial drugs chloroquine and pyrimethamine were determined by sequencing the relevant portions of the crt and dhfr genes, respectively. We found that parasite genetic diversity was comparable between the two sites, with high levels of polymorphism being maintained in both areas despite dramatic differences in transmission intensity. Crucially, we found that the frequencies of genetic markers of drug resistance against pyrimethamine and chloroquine differed significantly between the sites, indicative of differing selection pressures in the two areas.     

Structure of the carboxypeptidase Y inhibitor IC in complex with the cognate proteinase reveals a novel mode of the proteinase-protein inhibitor interaction

Carboxypeptidase Y (CPY) inhibitor, IC, shows no homology to any other known proteinase inhibitors and rather belongs to the phosphatidylethanolamine-binding protein (PEBP) family. We report here on the crystal structure of the IC-CPY complex at 2.7 A resolution. The structure of IC in the complex with CPY consists of one major beta-type domain and a N-terminal helical segment. The structure of the complex contains two binding sites of IC toward CPY, the N-terminal inhibitory reactive site (the primary CPY-binding site) and the secondary CPY-binding site, which interact with the S1 substrate-binding site of CPY and the hydrophobic surface flanked by the active site of the enzyme, respectively. It was also revealed that IC had the ligand-binding site, which is conserved among PEBPs and the putative binding site of the polar head group of phospholipid. The complex structure and analyses of IC mutants for inhibitory activity and the binding to CPY demonstrate that the N-terminal inhibitory reactive site is essential both for inhibitory function and the complex formation with CPY and that the binding of IC to CPY constitutes a novel mode of the proteinase-protein inhibitor interaction. The unique binding mode of IC toward the cognate proteinase provides insights into the inhibitory mechanism of PEBPs toward serine proteinases and into the specific biological functions of IC belonging to the PEBP family as well.     

Requirement of c-Jun NH2-terminal kinase activation in interferon-alpha-induced apoptosis through upregulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in Daudi B lymphoma cells

Interferon alpha (IFN-alpha) inhibits growth, at least in part, through induction of apoptosis. However, the molecular mechanisms underlying IFN-alpha-induced apoptosis are not completely understood. In the present study, we found that IFN-alpha induced a sustained activation of c-Jun N-terminal kinase 1 (JNK1), but not extracellular kinases (ERKs), in Daudi B lymphoma cells, as assessed by Western blotting using phospho-specific antibodies. Several lines of evidence support the notion that the IFN-alpha-induced activation of JNK is responsible for IFN-alpha-induced apoptosis, at least in part, through upregulation of TNF-related apoptosis-inducing ligand (TRAIL). First, pretreatment of Daudi cells with a JNK inhibitor reduced IFN-alpha-induced upregulation of TRAIL and loss of mitochondrial membrane potential (DeltaPsim) and annexin-positive cells, which was assessed by flow cytometry. Second, a dominant-negative form of JNK1 (dnJNK1) also reduced these apoptotic events, while a constitutively active form of JNK1, MKK7-JNK1beta, enhanced them. Finally, treatment with IFN-alpha enhanced the promoter activity of the TRAIL gene, which was partially abrogated by either JNK inhibitor or dnJNK1, while it was moderately enhanced by MKK7-JNK1beta. These findings are useful for understanding molecular mechanisms of IFN-alpha-induced apoptosis and also for development of treatment modalities of some tumors with IFN-alpha.     

Oral adsorbent AST-120 decreases serum levels of AGEs in patients with chronic renal failure

Advanced glycation end products (AGEs) are senescent macroprotein derivatives that are formed at an accelerated rate in patients with chronic renal failure (CRF). AGE formation and accumulation in plasma and vascular tissues contribute to accelerated atherosclerosis in this devastating disorder. AST-120 is an oral adsorbent that attenuates the progression of CRF by removing uremic toxins. Recently, AST-120 has been reported to reduce the progression of atherosclerosis as well. However, whether AST-120 decreases serum levels of AGEs and subsequently exerts atheroprotective properties remains to be elucidated. Ten nondiabetic CRF patients were enrolled in this study. All patients were kept on regular therapeutic diet and medications throughout the study. Serum AGE levels before and after AST-120 treatments were measured using enzyme-linked immunosorbent assay. Effects of patient-derived serum on atherosclerosis-related gene expression in cultured human umbilical vein endothelial cells (HUVECs) were analyzed by semiquantitative RT-PCR. Administration of AST-120 (6 g/day) for 3 months significantly decreased serum levels of AGEs in nondiabetic CRF patients, whereas AGE levels remained unchanged in age- and renal function-matched CRF patients without AST-120 treatment (n = 6). Patient serum after AST-120 treatment significantly reduced mRNA levels of receptor for AGEs, monocyte chemoattractant protein-1, and vascular adhesion molecule-1 in HUVECs compared with serum before treatment. Moreover, in vitro, AST-120 was found to adsorb carboxymethyllysine (CML), one of the well-characterized, digested food-derived AGEs. This study suggests that atheroprotective properties of AST-120 can be ascribed, at least in part, to its AGE-lowering ability via absorption of CML.     

Biotransformation of (±)-α-ionone and β-ionone by cultured cells of Caragana chamlagu

Suspension cultures of Caragana chamlagu (Leguminosae) convert (±)-α-ionone (1) into (±)-3-oxo-α-ionone (3) as the major product and β-ionone (2) into 5,6-epoxy-β-ionone (6) as the sole product. It is interesting to note that the cultured cells of C. chamlagu convert regioselectively the cycloolefinic part of 1 into the corresponding unsaturated carbonyl compound, allylic alcohol and epoxide as the oxidation products, whereas the suspension cultures of Nicotiana tabacum (Solanaceae) convert the unsaturated carbonyl of 1 into the corresponding saturated ketones and alcohols as reduction products.     

An integrase of endogenous retrovirus is involved in maternal mitochondrial DNA inheritance of the mouse

The mechanism of maternal mitochondrial DNA (mtDNA) inheritance in animals can be said to be the selective elimination of sperm mtDNA via the elimination factor of the egg and a sperm mitochondria-specific factor. In 2005, we clarified that t-tpis (Spag1 isoform 1) is a mitochondria-specific translocator and the sperm factor, and furthermore estimated that the elimination factors of the egg are the divalent cation-dependent endonuclease and s-tpis (Spag1 isoform 2 and isoform 3) as the elimination system-specific chaperone [K. Hayashida, K. Omagari, J. Masuda, H. Hazama, Y. Kadokawa, K. Ohba, S. Kohno, The sperm mitochondria-specific translocator has a key role in maternal mitochondrial inheritance, Cell Biol. Int. 29 (2005) 472-481]. This time, using a recombinant Spag1 isoform 1 protein, a pull-down assay of ovary cytosol was performed and the elimination factors searched for. Surprisingly, an endogenous retroviral integrase fragment (Eri15) was identified using mass spectrometry of the electrophoresis band of the pull-down protein. Eri15 was detected as a complex of ∼500 kDa with Spag1 isoform 2 or isoform 3 in native PAGE of the ovary cytosol. This strongly suggested that Eri15 is selectively transported into the sperm mitochondria matrix by Spag1 isoform 2 and 3 via Spag1 isoform 1 and that sperm mtDNA is destroyed, thus causing the establishment of maternal mtDNA inheritance.