Endogenous DNA damage in humans: a review of quantitative data
By academic.oup.com
DNA damage plays a major role in mutagenesis, carcinogenesis and ageing. The chemical events that lead to DNA damage include hydrolysis, exposure to reactive oxygen substances (ROS) and other reactive metabolites. These reactions are triggered by exposure to exogenous chemicals or they can result from metabolic, endogenous processes. The concentrations and mutagenic potentials of known carcinogens to which we are exposed in our environment are insufficient to explain the high incidence of sporadic cancer that is actually seen in our population (Epe, 2002). Innate factors can also not suffice to explain this high incidence. Epidemiology shows that, in developed societies, exogenous factors are a necessary condition in about 75–80% of cancer cases (Doll and Peto, 1981; Trichopoulos et al., 1994). So, mutations due to DNA damage, caused by unidentified exogenous agents, and to an increase in endogenous damage modulated by exogenous factors must play a role in most cases of cancer, in addition to changes in gene expression due to exogenous conditions. A thorough knowledge of the types and prevalence of endogenous DNA damage can be considered essential for an understanding of the interaction of exogenous agents and influences with endogenous processes in the induction of cancer and other diseases. In particular, this is important for risk analysis concerning low dose environmental factors. Endogenous DNA damage occurs at a high frequency compared with exogenous damage and the types of damage produced by normal cellular processes are identical or very similar to those caused by some environmental agents (Jackson and Loeb, 2001). The study of endogenous damage is also of importance to chemoprevention. It is evident that if an approach could be developed leading to a decrease in endogenous DNA damage and endogenous mutations, the incidence of cancer and other diseases might be substantially reduced, even without a reduction in exogenous mutations.
Oxidative DNA damage
In living cells ROS are formed continuously as a consequence of metabolic and other biochemical reactions as well as external factors. These ROS include superoxide (O2–·), hydrogen peroxide (H2O2), hydroxyl radicals (OH·) and singlet oxygen (1O2) and they can oxidize DNA, which can lead to several types of DNA damage, including oxidized bases and single‐ and double‐strand breaks. DNA damage produced by ROS is the most frequently occurring damage.
Oxidatively modified DNA is, despite extensive DNA repair, abundant in many human tissues, especially in tumours (Iida et al., 2001; Li et al., 2002). Many defence mechanisms within the organism have evolved to limit the levels of reactive oxidants and the damage they induce (Slupphaug et al., 2003). Oxidative stress occurs when the production of ROS exceeds the body’s natural antioxidant defence mechanisms, causing damage to macromolecules such as DNA, proteins and lipids. ROS also inactivate antioxidant enzymes (Kono and Fidovich, 1982; Tabatabaie and Floyd, 1994). So, as pointed out by Epe (2002), any change in the endogenous generation of ROS or cellular antioxidants or in the efficiency of DNA repair should cause a corresponding modulation of the steady‐state levels of oxidative DNA modifications, which in turn should modulate the mutation rate and ultimately the cancer incidence. Epidemiological evidence from different studies points to reduced risks for cancer, particularly in the upper gastrointestinal tract and airways, associated with a diet rich in antioxidants and/or a high content of antioxidants in plasma samples (Loft and Poulsen, 1996).
Data suggest that the rate of damage decreases with age, possibly along with the decreasing rate of metabolism, whereas the steady‐state levels increase due to failing repair (Loft and Poulsen, 1996).
Source: https://academic.oup.com/mutage/article/doi/10.1093/mutage/geh025/1482185/Endogenous-DNA-damage-in-humans-a-review-of
Thursday, July 2, 2026
Key Facts About Prednisone tablets Every Patient Should Know
Health decisions are easier when reliable information is close at hand. Blood pressure can rise modestly during treatment, so routine monitoring is a sensible precaution. Bone health can be affected by prolonged use, making calcium and vitamin D intake more important. Older adults may be more sensitive to certain side effects and often start on lower doses. Support groups and patient communities can offer helpful firsthand experiences. Corticosteroids mimic hormones the body produces naturally in the adrenal glands. Children are typically prescribed weight-based dosing under close medical supervision. This prednisone tablets breaks down the key points in an easy-to-follow format. Mood changes, including irritability or anxiety, are worth mentioning to a healthcare provider. Insurance coverage and pricing can vary widely, so comparing options is often worthwhile. Every patient metabolizes medication differently, which is why dosing guidelines vary by condition. Sleep disruption is a frequently reported side effect, especially when doses are taken later in the day. Immune suppression is a known effect, which is why avoiding sick contacts is often advised. Taking medication with food can help reduce stomach discomfort for many patients. Pregnant or breastfeeding patients should always discuss medication safety with their provider. Every treatment decision should weigh the benefits against the possible risks for that individual. Mild swelling or water retention sometimes accompanies steroid use and usually resolves after tapering. Combining certain drugs without medical guidance can increase the risk of unwanted interactions. Some conditions respond well to a short burst of treatment, while others need a longer tapering schedule. Missing a dose occasionally is common, but a consistent schedule improves overall outcomes. Chronic conditions such as arthritis or asthma often call for longer treatment planning. Long-term use requires closer monitoring due to potential effects on bone density and blood sugar. A dedicated resource on find out more can help clarify what to expect. Gastrointestinal discomfort is one reason many prescribers suggest pairing medication with a meal. Short courses of steroid therapy are generally well tolerated by most adults. Storing medication in a cool, dry place helps preserve its effectiveness. Every patient's situation is different, so personalized medical advice should always guide final decisions.
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