Effects of short-term zidovudine exposure on mitochondrial DNA content and succinate dehydrogenase activity of rat skeletal muscle cells

Introducing energy into marine environments: A lab-scale static magnetic field submarine cable simulation and its effects on sperm and larval development on a reef forming serpulid

Non-chemical sources of anthropogenic environmental stress, such as artificial lights, noise and magnetic fields, are still an underestimate factor that may affect the wildlife. Marine environments are constantly subjected to these kinds of stress, especially nearby to urbanized coastal areas. In the present work, the effect of static magnetic fields, associated with submerged electric cables, was evaluated in gametes and early life stages of a serpulid polychaete, namely Ficopomatus enigmaticus. Specifically, biochemical/physiological impairments of sperm, fertilization rate inhibition and incorrect larval development were assessed. We evaluated differences between two selected magnetic field induction values (0.5 and 1 mT) along a range of exposure times (30 min-48 h), for a sound evaluation on this species. We found that a magnetic induction of 1 mT, a typical value that can be found at distance of tens of cm from a submerged cable, may be considered a biologically and ecologically relevant for sessile organisms and for coastal environments more generally. This value exerted statistically significant effects on membranes, DNA integrity, kinetic parameters and mitochondrial activity of sperm cells. Moreover, a significant reduction in fertilization rate was observed in sperm exposed to the same magnetic induction level (1 mT) for 3 h, compared to controls. Regarding early larval stages, 48-h exposure did not affect the correct development. Our results represent a starting point for a future focus of research on magnetic field effects on early life stages of aquatic invertebrates, using model species as representative for reef-forming/encrusting organisms and ecological indicators of soft sediment quality.

Integrated analysis of the involvement of nitric oxide synthesis in mitochondrial proliferation, mitochondrial deficiency and apoptosis in skeletal muscle fibres

Nitric oxide (NO) is an important signaling messenger involved in different mitochondrial processes but only few studies explored the participation of NO in mitochondrial abnormalities found in patients with genetic mitochondrial deficiencies. In this study we verified whether NO synthase (NOS) activity was altered in different types of mitochondrial abnormalities and whether changes in mitochondrial function and NOS activity could be associated with the induction of apoptosis. We performed a quantitative and integrated analysis of NOS activity in individual muscle fibres of patients with mitochondrial diseases, considering mitochondrial function (cytochrome-c-oxidase activity), mitochondrial content, mitochondrial DNA mutation and presence of apoptotic nuclei. Our results indicated that sarcolemmal NOS activity was increased in muscle fibres with mitochondrial proliferation, supporting the relevance of neuronal NOS in the mitochondrial biogenesis process. Sarcoplasmic NOS activity was reduced in cytochrome-c-oxidase deficient fibres, probably as a consequence of the involvement of NO in the regulation of the respiratory chain. Alterations in NOS activity or mitochondrial abnormalities were not predisposing factors to apoptotic nuclei. Taken together, our results show that NO can be considered a potential molecular target for strategies to increase mitochondrial content and indicate that this approach may not be associated with increased apoptotic events.

Changes in Mitochondrial Toxicity in Peripheral Blood Mononuclear Cells During Four-Year Administration of Entecavir Monotherapy in Chinese Patients with Chronic Hepatitis B

BACKGROUND

This study aimed to assess whether long-term entecavir monotherapy induces mitochondrial toxicity in patients with chronic hepatitis B (CHB).

MATERIAL AND METHODS

This was a prospective study in 34 antiviral treatment-naïve patients with CHB who received entecavir monotherapy and were followed up for 4 years. Blood samples were collected after 0, 2, 3, and 4 years of entecavir (ETC) monotherapy (ETC0, ETC2, ETC3, and ETC4, respectively). Mitochondrial DNA (mtDNA) contents were determined using real-time quantitative polymerase chain reaction (qRT-PCR) and mtDNA4977 depletions were detected using nested PCR. Levels of hepatitis B virus (HBV) DNA, alanine aminotransferase, alanine aminotransferase, hepatitis B e antigen (HBeAg), creatine kinase, urea nitrogen, and serum creatinine were recorded.

RESULTS

mtDNA contents at ETC0 (9.6±6.3) and ETC4 (10.3±6.2) were markedly higher than at ETC2 (0.8±0.5, P<0.01) and ETC3 (1.3±0.9, P<0.01), but there were no differences between ETC2 and ETC3 or between ETC0 and ETC4. MtDNA4977 depletion appeared in 79.4% cases at ETC2 and in 70.6% at ETC3, which were much higher than at ETC0 (32.4%, P<0.01) and ETC4 (8.8%, P<0.01), but there were no differences in mtDNA4977 depletion ratio between ETC2 and ETC3, or between ETC0 and ETC4. mtDNA content was negatively correlated to mtDNA4977 depletion (partial regression coefficient of -4.555, P<0.001, R2=0.315). mtDNA content was positively correlated with age (partial regression coefficient of 0.131, P=0.045).

CONCLUSIONS

Results suggest that during 4-year entecavir monotherapy for CHB, the mtDNA contents initially decreased and then increased, while the mtDNA4977 depletion rates first increased and then decreased.