Detection of oxidative stress-induced mitochondrial DNA damage using fluorescence correlation spectroscopy

Adenoviral vector expressing IGF-1 protects murine chondrogenic ATDC5 cells against hydrogen peroxide-induced mitochondrial dysfunction and apoptosis

Insulin-like growth factor-1 (IGF-1), with an age-related decline, regulates the proliferation and survival of multiple cell types, particularly stimulates cartilage matrix synthesis, and inhibits matrix degradation. The present study was to investigate the regulatory role of IGF-1 against hydrogen peroxide(H2O2)-induced mitochondrial dysfunction and apoptosis in murine chondrocytic ATDC5 cells. We firstly determined mitochondrial dysfunction and apoptosis in ATDC5 cells which were exposed to H2O2. We then constructed an IGF-1-overexpressed adenovirus (IGF-1-Ad) harboring the IGF-1 coding sequence, and investigated the regulatory role of the overexpressed IGF-1 against the H2O2-induced mitochondrial dysfunction and apoptosis in ATDC5 cells. It was demonstrated that H2O2 treatment promoted the mitochondrial dysfunction, and further reduced the viability and induced apoptosis of ATDC5 cells. However, the IGF-1 overexpression by adenovirus inhibited the H2O2-induced mitochondrial dysfunction and further inhibited the H2O2-promoted apoptosis in ATDC5 cells. In conclusion, the present study found that oxidative stress promoted mitochondrial dysfunction and induced apoptosis in the murine chondrocytic ATDC5 cells, and the adenoviral vector-expressed IGF-1 protected the murine chondrocytic ATDC5 cells against such mitochondrial dysfunction and apoptosis. This study implies the protective role of IGF-1 against the oxidative stress in murine chondrocytic ATDC5 cells and demonstrates the promising anti-oxidative stress effect of the recombinant IGF-1-Ad against oxidative stress in chondrocytic cells.

Metabolic toxicity screening using electrochemiluminescence arrays coupled with enzyme-DNA biocolloid reactors and liquid chromatography-mass spectrometry

New chemicals or drugs must be guaranteed safe before they can be marketed. Despite widespread use of bioassay panels for toxicity prediction, products that are toxic to a subset of the population often are not identified until clinical trials. This article reviews new array methodologies based on enzyme/DNA films that form and identify DNA-reactive metabolites that are indicators of potentially genotoxic species. This molecularly based methodology is designed in a rapid screening array that utilizes electrochemiluminescence (ECL) to detect metabolite-DNA reactions, as well as biocolloid reactors that provide the DNA adducts and metabolites for liquid chromatography-mass spectrometry (LC-MS) analysis. ECL arrays provide rapid toxicity screening, and the biocolloid reactor LC-MS approach provides a valuable follow-up on structure, identification, and formation rates of DNA adducts for toxicity hits from the ECL array screening. Specific examples using this strategy are discussed. Integration of high-throughput versions of these toxicity-screening methods with existing drug toxicity bioassays should allow for better human toxicity prediction as well as more informed decision making regarding new chemical and drug candidates.

Biomarker Validation for Aging: Lessons from mtDNA Heteroplasmy Analyses in Early Cancer Detection

The anticipated biological and clinical utility of biomarkers has attracted significant interest recently. Aging and early cancer detection represent areas active in the search for predictive and prognostic biomarkers. While applications differ, overlapping biological features, analytical technologies and specific biomarker analytes bear comparison. Mitochondrial DNA (mtDNA) as a biomarker in both biological models has been evaluated. However, it remains unclear whether mtDNA changes in aging and cancer represent biological relationships that are causal, incidental, or a combination of both. This article focuses on evaluation of mtDNA-based biomarkers, emerging strategies for quantitating mtDNA admixtures, and how current understanding of mtDNA in aging and cancer evolves with introduction of new technologies. Whether for cancer or aging, lessons from mtDNA based biomarker evaluations are several. Biological systems are inherently dynamic and heterogeneous. Detection limits for mtDNA sequencing technologies differ among methods for low-level DNA sequence admixtures in healthy and diseased states. Performance metrics of analytical mtDNA technology should be validated prior to application in heterogeneous biologically-based systems. Critical in evaluating biomarker performance is the ability to distinguish measurement system variance from inherent biological variance, because it is within the latter that background healthy variability as well as high-value, disease-specific information reside.

Fluorescence correlation spectroscopy: novel variations of an established technique

Fluorescence correlation spectroscopy (FCS) is one of the major biophysical techniques used for unraveling molecular interactions in vitro and in vivo. It allows minimally invasive study of dynamic processes in biological specimens with extremely high temporal and spatial resolution. By recording and correlating the fluorescence fluctuations of single labeled molecules through the exciting laser beam, FCS gives information on molecular mobility and photophysical and photochemical reactions. By using dual-color fluorescence cross-correlation, highly specific binding studies can be performed. These have been extended to four reaction partners accessible by multicolor applications. Alternative detection schemes shift accessible time frames to slower processes (e.g., scanning FCS) or higher concentrations (e.g., TIR-FCS). Despite its long tradition, FCS is by no means dated. Rather, it has proven to be a highly versatile technique that can easily be adapted to solve specific biological questions, and it continues to find exciting applications in biology and medicine.