PINK1- and PARK2-mediated local mitophagy in distal neuronal axons

Mutations in the PINK1 and PARK2/PARKIN genes are associated with hereditary early onset Parkinson disease (PD), and in cell lines the corresponding gene products play a critical role in mitophagic clearance of damaged mitochondria. In neurons, however, where the extraordinary cellular shapes pose particular challenges for maintaining healthy mitochondria, the pathways of mitophagy are less well understood. Both the location at which mitophagy occurs and the involvement of PINK1 and PARK2 have been controversial. Here we review our recent study where we found that selective damage to a subset of axonal mitochondria causes them to be engulfed within autophagosomes and cleared locally within the axon without the need for transport back to the soma. We also found this process to be completely dependent on neuronal PINK1 and PARK2.     

Improved characterization of cartilage mechanical properties using a combination of stress relaxation and creep

Mechanical characterization of cartilage, other soft tissues and gels has become a ubiquitous and essential aspect of biomechanics and biomaterials research. Current progress in theoretical modeling and tools for data analysis often exceed what is required for routine mechanical characterization assays in experimental studies, making selection of methodologies difficult for the nonspecialist. We have therefore developed an approach for measurement of confined compression modulus and hydraulic permeability based on simple poroelasticity theory and requiring only linear regression tools for data analysis. This technique involves a new application of an early-time solution for creep combined with stress relaxation measurements to characterize soft tissue mechanical parameters as a function of compressive strain or water content. This combined methodology allows measurement of hydraulic permeability by two different techniques with only a modest increase in experimental duration, providing a more precise assessment of permeability and associated measurement error.     

Association of a Genetic Variant in the Cyclin-Dependent Kinase Inhibitor 2B with Risk of Pancreatic Cancer

Background:Pancreatic cancer (PC) is among the most aggressive tumors with a poor prognosis, indicating the need for the identification of a novel prognostic biomarker for risk stratifications. Recent genome-wide association studies have demonstrated common genetic variants in a region on chromosome 9p21 associated with an increased risk of different malignancies.Methods:In the present study, we explore the possible relationship between genetic variant, rs10811661, and gene expression of CDKN2B in 75 pancreatic cancer patients, and 188 healthy individuals. DNAs were extracted and genotyping and gene expression were performed by TaqMan real-time PCR and RT-PCR, respectively. Logistic regression was used to assess the association between risk and genotypes, while the significant prognostic variables in the univariate analysis were included in multivariate analyses.Results:The patients with PDAC had a higher frequency of a TT genotype for rs10811661 than the control group. Also, PDAC patients with dominant genetic model, (TT + TC), was associated with increased risk of developing PDAC (OR= 14.71, 95% CI [1.96-110.35], p= 0.009). Moreover, patients with CC genotype had a higher expression of CDKN2B, in comparison with TT genotype.Conclusion:Our findings demonstrated that CDKN2A/B was associated with the risk of developing PDAC, supporting further investigations in the larger and multicenter setting to validate the potential value of this gene as an emerging marker for PDAC. Key Words: CDKN2A/B, Rs10811661, Pancreatic cancer, Prognostic biomarker     

Pre-and Post-Transplant Serum Lactate Dehydrogenase Levels as a Predictive Marker for Patient Survival and Engraftment in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Background:The discovery of biomarkers to predict the development of complications associated with hematopoietic stem cell transplantation (HSCT) offers a potential avenue for the early identification and treatment of these life-threatening consequences. Serum lactate dehydrogenase (sLDH) has been identified as a potential biomarker for determining the outcome of allogenic HSCT (allo-HSCT).Methods:A retrospective study was performed using data collected from 204 allo-HSCT recipient patients to examine the predictive value of sLDH levels pre- and post-allo-HSCT on patient survival, graft-versus-host-disease (GVHD) incidence, and time to platelet/white blood cells (WBC) engraftment.Results:Our findings show that neither pre- (p= 0.61) nor post-transplantation (p= 0.55) sLDH levels were associated with GVHD incidence. However, elevated sLDH levels pre- and post-transplantation (≥ 386 and ≥ 409 IU/mL, respectively) were found to be adverse risk factors for patient survival (p= 0.16, p= 0.20, respectively). Furthermore, a median sLDH level ≥ 400 IU/mL from day +5 to day +15 post-transplantation had a significant positive association with enhanced time to platelet and white blood cell (WBC) engraftment, compared to patients with sLDH levels < 400 IU/mL (p< 0.001).Conclusion:Our data suggests that high sLDH levels pre- and post-allo-HSCT could be considered a predictor of poor patient survival. Furthermore, high levels of sLDH days 5-15 post-allo-HSCT could be associated with improved time to platelet and WBC engraftment; however, this appears to come at the cost of increased mortality risk.Key Words: Engraftment, Graft versus host disease, Hematopoietic stem cell transplantation, Lactate dehydrogenase     

The Impact of Duration of Treatment on Reported Time-to-Onset in Spontaneous Reporting Systems for Pharmacovigilance

Within pharmacovigilance, knowledge of time-to-onset (time from start of drug administration to onset of reaction) is important in causality assessment of drugs and suspected adverse drug reactions (ADRs) and may indicate pharmacological mechanisms involved. It has been suggested that time-to-onset from individual case reports can be used for detection of safety signals. However, some ADRs only occur during treatment, while those that do occur later are less likely to be reported. The aim of this study was to investigate the impact of treatment duration on the reported time-to-onset. Case reports from the WHO Global ICSR database, VigiBase, up until February 5^th 2010 were the basis of this study. To examine the effect of duration of treatment on reported time-to-onset, angioedema and hepatitis were selected to represent short and long latency ADRs, respectively. The reported time-to-onset for each of these ADRs was contrasted for a set of drugs expected to be used short- or long-term, respectively. The study included 2,980 unique reports for angioedema and 1,159 for hepatitis. Median reported time-to-onset for angioedema in short-term treatments ranged 0-1 days (median 0.5), for angioedema in long-term treatments 0-26 days (median 8), for hepatitis in short-term treatments 4-12 days (median 7.5) and for hepatitis in long term treatments 19-73 days (median 28). Short-term treatments presented significantly shorter reported time-to-onset than long-term treatments. Of note is that reported time-to-onset for angioedema for long-term treatments (median value of medians being 8 days) was very similar to that of hepatitis for short-term treatments (median value of medians equal 7.5 days). The expected duration of treatment needs to be considered in the interpretation of reported time-to-onset and should be accounted for in signal detection method development and case evaluation.     

Mitophagy of damaged mitochondria occurs locally in distal neuronal axons and requires PINK1 and Parkin

To minimize oxidative damage to the cell, malfunctioning mitochondria need to be removed by mitophagy. In neuronal axons, mitochondrial damage may occur in distal regions, far from the soma where most lysosomal degradation is thought to occur. In this paper, we report that PINK1 and Parkin, two Parkinson’s disease–associated proteins, mediate local mitophagy of dysfunctional mitochondria in neuronal axons. To reduce cytotoxicity and mimic physiological levels of mitochondrial damage, we selectively damaged a subset of mitochondria in hippocampal axons. Parkin was rapidly recruited to damaged mitochondria in axons followed by formation of LC3-positive autophagosomes and LAMP1-positive lysosomes. In PINK1^−/− axons, damaged mitochondria did not accumulate Parkin and failed to be engulfed in autophagosomes. Similarly, initiation of mitophagy was blocked in Parkin^−/− axons. Our findings demonstrate that the PINK1–Parkin-mediated pathway is required for local mitophagy in distal axons in response to focal damage. Local mitophagy likely provides rapid neuroprotection against oxidative stress without a requirement for retrograde transport to the soma.     

The ColV, I-K94 plasmid and heat sensitivity of Escherichia coli

The ColV, I-K94 plasmid markedly increased the heat sensitivity of Escherichia coli K12 but had no sensitizing effect on a wild E. coli isolate. The plasmid effect on strain K12 appeared to result from ColV-encoded transfer and colicin components possibly due to their effects on membrane properties.