Oxidation and nitration in dopaminergic areas of the prefrontal cortex from patients with bipolar disorder and schizophrenia.

BACKGROUND: Increased oxidative stress is strongly implicated in bipolar disorder (BD), where protein oxidation, lipid peroxidation and oxidative damage to DNA have been consistently reported. High levels of dopamine (DA) in mania are also well-recognized in patients with BD, and DA produces reactive oxygen species and electron-deficient quinones that can oxidize proteins when it is metabolized. METHODS: Using immunohistochemistry and acceptor photobleaching Förster resonance energy transfer (FRET), we examined oxidation and nitration of areas immunoreactive for the DA transporter (DAT) and tyrosine hydroxylase (TH) in the postmortem prefrontal cortex from patients with BD, schizophrenia and major depression as well as nonpsychiatric controls. RESULTS: We found increased oxidation of DAT-immunoreactive regions in patients with BD (F3,48 = 6.76, p = 0.001; Dunnett post hoc test p = 0.001) and decreased nitration of TH-immunoreactive regions in both patients with BD (F3,45 = 3.10, p = 0.036; Dunnett post hoc test p = 0.011) and schizophrenia (p = 0.027). On the other hand, we found increased global levels of oxidation in patients with BD (F3,44 = 6.74, p = 0.001; Dunnett post hoc test p = 0.001) and schizophrenia (p = 0.020), although nitration levels did not differ between the groups (F3,46 = 1.75; p = 0.17). LIMITATIONS: Limitations of this study include the use of postmortem brain sections, which may have been affected by factors such as postmortem interval and antemortem agonal states, although demographic factors and postmortem interval were accounted for in our statistical analysis. CONCLUSION: These findings suggest alterations in levels of protein oxidation and nitration in DA-rich regions of the prefrontal cortex in patients with BD and schizophrenia, but more markedly in those with BD.

Aptamer-mediated inhibition of Mycobacterium tuberculosis polyphosphate kinase 2.

Inorganic polyphosphate (polyP) plays a number of critical roles in bacterial persistence, stress, and virulence. PolyP intracellular metabolism is regulated by the polyphosphate kinase (PPK) protein families, and inhibition of PPK activity is a potential approach to disrupting polyP-dependent processes in pathogenic organisms. Here, we biochemically characterized Mycobacterium tuberculosis (MTB) PPK2 and developed DNA-based aptamers that inhibit the enzyme's catalytic activities. MTB PPK2 catalyzed polyP-dependent phosphorylation of ADP to ATP at a rate 838 times higher than the rate of polyP synthesis. Gel filtration chromatography suggested MTB PPK2 to be an octamer. DNA aptamers were isolated against MTB PPK2. Circular dichroism revealed that aptamers grouped into two distinct classes of secondary structure; G-quadruplex and non-G-quadruplex. A selected G-quadruplex aptamer was highly selective for binding to MTB PPK2 with a dissociation constant of 870 nM as determined by isothermal titration calorimetry. The binding between MTB PPK2 and the aptamer was exothermic yet primarily driven by entropy. This G-quadruplex aptamer inhibited MTB PPK2 with an IC(50) of 40 nM and exhibited noncompetitive inhibition kinetics. Mutational mechanistic analysis revealed an aptamer G-quadruplex motif is critical for enzyme inhibition. The aptamer was also tested against Vibrio cholerae PPK2, where it showed an IC(50) of 105 nM and insignificant inhibition against more distantly related Laribacter hongkongensis PPK2.

Association of hepatitis B virus pre-S deletions with the development of hepatocellular carcinoma in chronic hepatitis B.

BACKGROUND: We aimed to determine whether hepatitis B virus (HBV) pre-S deletion was an independent factor for the development of hepatocellular carcinoma (HCC). METHODS: Pre-S deletions were determined in HBV isolates from 115 chronic hepatitis B (CHB) patients with HCC. Sixty-nine patients were further matched with 69 CHB patients without HCC for age, sex, hepatitis B e antigen (HBeAg) status, and HBV genotype. RESULTS: HBV pre-S deletions were clustered mainly in the 3' end of pre-S1 and 5' end of pre-S2 regions. Adjusted for confounding risk factors, patients with HCC had a higher prevalence of HBV with pre-S deletions than did patients without HCC (23 [33.3%] of 69 vs 11 [15.9%] of 69; P = .018; odds ratio [OR], 2.64). In particular, only pre-S2 deletions but not pre-S1 deletions were significantly associated with the development of HCC (P = .020). A higher prevalence of pre-S deletions was observed in HBV isolates from HCC patients under the age of 50 years than from those older than 50 years (10 [62.5%] of 16 vs 13 [24.5%] of 53; P = .012; OR, 5.13). Emergence of de novo pre-S deletions was documented before the development of HCC. CONCLUSIONS: HBV pre-S2 deletions were an independent factor associated with the development of HCC. Its oncogenic role may be more important in young patients with HCC.

Profile of pre-S deletions in the natural history of chronic hepatitis B infection.

It have been suggested that hepatitis B virus (HBV) pre-S deletions may play a role in hepatocarcinogenesis. The aim of the study was to determine the prevalence of pre-S deletions in chronic hepatitis B patients in Hong Kong, the factors associated with the deletions and its relationship with hepatitis B e antigen (HBeAg) seroconversion. HBV pre-S deletions were determined by nucleotide sequence analysis in 178 patients with chronic HBV (cross-sectional study). Eighty-four patients had paired samples before and after HBeAg seroconversion (longitudinal study). The prevalence of pre-S deletions was 12.9% (23/178). A majority of the pre-S deletions (73.9%) occurred in the 5' terminus of pre-S2 region whereas deletions in the pre-S1 region appeared less frequently (47.8%). There was no relationship between age and pre-S deletions. Male gender [odds ratio (OR) =10.88; 95% confidence interval (CI) =1.37-86.52; P=0.024] and HBV genotype C (OR=13.85; 95% CI=3.05-62.92; P=0.001) were independent factors associated with pre-S deletions. Only 17 out of the 84 patients with paired samples before and after HBeAg seroconversion had pre-S deletions. The patterns of pre-S deletions before and after HBeAg seroconversion were variable. Compared with genotype B, HBV genotype C was associated with earlier emergence of pre-S deletions. In conclusion, 12.9% of chronic HBV carriers had pre-S deletions (predominantly pre-S2 deletions) in a geographical area highly endemic for chronic hepatitis B. Male gender and HBV genotype C were associated independently with the development of pre-S deletion mutations. There was no clear relationship between HBeAg seroconversion and pre-S deletions.

Distribution and diversity of phytate-mineralizing bacteria.

Phytate, the most abundant organic phosphorus compound in soil, dominates the biotic phosphorus input from terrestrial runoffs into aquatic systems. Microbial mineralization of phytate by phytases is a key process for recycling phosphorus in the biosphere. Bioinformatic studies were carried out on microbial genomes and environmental metagenomes in the NCBI and the CAMERA databases to determine the distribution of the four known classes of phytase in the microbial world. The beta-propeller phytase is the only phytase family that can be found in aquatic environments and it is also distributed in soil and plant bacteria. The beta-propeller phytase-like genes can be classified into several subgroups based on their domain structure and the positions of their conserved cysteine residues. Analysis of the genetic contexts of these subgroups showed that beta-propeller phytase genes exist either as an independent gene or are closely associated with a TonB-dependent receptor-like gene in operons, suggesting that these two genes are functionally linked and thus may play an important role in the cycles of phosphorus and iron. Our work suggests that beta-propeller phytases play a major role in phytate-phosphorus cycling in both soil and aquatic microbial communities.