The impacts of prominent gene polymorphisms in DNA repair enzymes on Parkinson’s disease

Activated or Impaired: An Overview of DNA Repair in Neurodegenerative Diseases

As the population ages, age-related neurodegenerative diseases have become a major challenge in health science. Currently, the pathology of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, is still not fully understood. Remarkably, emerging evidence indicates a role of genomic DNA damage and repair in various neurodegenerative disorders. Here, we summarized the current understanding of the function of DNA damage repair, especially base excision repair and double strand break repair pathways, in a variety of neurodegenerative diseases. We concluded that exacerbation of DNA lesions is found in almost all types of neurodegenerative diseases, whereas the activities of different DNA repair pathways demonstrate distinct trends, depending on disease type and even brain region. Specifically, key enzymes involved in base excision repair are likely impaired in Alzheimer's disease and amyotrophic lateral sclerosis but activated in Parkinson's disease, while nonhomologous end joining is likely downregulated in most types of neurodegenerative diseases. Hence, impairment of nonhomologous end joining is likely a common etiology for most neurodegenerative diseases, while defects in base excision repair are likely involved in the pathology of Alzheimer's disease and amyotrophic lateral sclerosis but are Parkinson's disease, based on current findings. Although there are still discrepancies and further studies are required to completely elucidate the exact roles of DNA repair in neurodegeneration, the current studies summarized here provide crucial insights into the pathology of neurodegenerative diseases and may reveal novel drug targets for corresponding neurodegenerative diseases.

Individual susceptibility has a major impact on strong association between oxidative stress, defence systems and Parkinson's disease

Oxidative stress plays an important role in the degeneration of dopaminergic neurons, which causes Parkinson's disease (PD). Oxidative stress products, antioxidant and their balance have important roles in the development of oxidative stress-based PD. The impact of reactive oxygen species (ROS) and defence systems can be altered by genetic polymorphisms, and thus the risk of PD may also be affected. We aimed to investigate the possible association of individual susceptibility with the development of oxidative stress-based PD. For this purpose, we measured serum levels of folic acid, homocysteine, Vitamin B6 and B12 that play roles in folate-dependent one-carbon pathway, oxidant or antioxidant enzymes (NADPH oxidase, MnSOD, GPX), 8-OHdG and repair enzymes (OGG1, XRCC1 and MTH1) by ELISA, and analysed related gene polymorphisms by PCR-RFLP. XRCC1, ROS, NADPH and folic acid levels were found to be statistically higher in patients than controls. XRCC1, MnSOD and GPX activities were increased. We observed higher levels of 8-OHdG in patients with MnSOD and XRCC1 mutant genotypes and higher XRCC1 levels in patients with NOX p22 fox mutant genotypes rather than controls. We suggest that routinely clinical validation of major oxidative stress-related biomarkers will be a good approach to manage detrimental effects of PD.

Aging-related modifications to G protein-coupled receptor signaling diversity

Aging is a highly complex molecular process, affecting nearly all tissue systems in humans and is the highest risk factor in developing neurodegenerative disorders such as Alzheimer's and Parkinson's disease, cardiovascular disease and Type 2 diabetes mellitus. The intense complexity of the aging process creates an incentive to develop more specific drugs that attenuate or even reverse some of the features of premature aging. As our current pharmacopeia is dominated by therapeutics that target members of the G protein-coupled receptor (GPCR) superfamily it may be prudent to search for effective anti-aging therapeutics in this fertile domain. Since the first demonstration of GPCR-based β-arrestin signaling, it has become clear that an enhanced appreciation of GPCR signaling diversity may facilitate the creation of therapeutics with selective signaling activities. Such 'biased' ligand signaling profiles can be effectively investigated using both standard molecular biological techniques as well as high-dimensionality data analyses. Through a more nuanced appreciation of the quantitative nature across the multiple dimensions of signaling bias that drugs possess, researchers may be able to further refine the efficacy of GPCR modulators to impact the complex aberrations that constitute the aging process. Identifying novel effector profiles could expand the effective pharmacopeia and assist in the design of precision medicines. This review discusses potential non-G protein effectors, and specifically their potential therapeutic suitability in aging and age-related disorders.