Nijmegen breakage syndrome fibroblasts expressing the C-terminal truncated NBN(p70) protein undergo p38/MK2-dependent premature senescence

T Lymphocytes in Patients With Nijmegen Breakage Syndrome Demonstrate Features of Exhaustion and Senescence in Flow Cytometric Evaluation of Maturation Pathway

Patients with Nijmegen Breakage Syndrome (NBS) suffer from recurrent infections due to humoral and cellular immune deficiency. Despite low number of T lymphocytes and their maturation defect, the clinical manifestations of cell-mediated deficiency are not as severe as in case of patients with other types of combined immune deficiencies and similar T cell lymphopenia. In this study, multicolor flow cytometry was used for evaluation of peripheral T lymphocyte maturation according to the currently known differentiation pathway, in 46 patients with genetically confirmed NBS and 46 sex and age-matched controls. Evaluation of differential expression of CD27, CD31, CD45RA, CD95, and CD197 revealed existence of cell subsets so far not described in NBS patients. Although recent thymic emigrants and naïve T lymphocyte cell populations were significantly lower, the generation of antigen-primed T cells was similar or even greater in NBS patients than in healthy controls. Moreover, the senescent and exhausted T cell populations defined by expression of CD57, KLRG1, and PD1 were more numerous than in healthy people. Although this hypothesis needs further investigations, such properties might be related to an increased susceptibility to malignancy and milder clinical course than expected in view of T cell lymphopenia in patients with NBS.

Pigmentation abnormalities in nucleotide excision repair disorders: Evidence and hypotheses

Skin pigmentation abnormalities are manifested in several disorders associated with deficient DNA repair mechanisms such as nucleotide excision repair (NER) and double-strand break (DSB) diseases, a topic that has not received much attention up to now. Hereditary disorders associated with defective DNA repair are valuable models for understanding mechanisms that lead to hypo- and hyperpigmentation. Owing to the UV-associated nature of abnormal pigmentary manifestations, the outcome of the activated DNA damage response (DDR) network could be the effector signal for alterations in pigmentation, ultimately manifesting as pigmentary abnormalities in repair-deficient disorders. In this review, the role of the DDR network in the manifestation of pigmentary abnormalities in NER and DSB disorders is discussed with a special emphasis on NER disorders.

The role of cellular senescence in aging through the prism of Koch-like criteria

Since Hayflick's discovery of cellular senescence (CS), a great volume of knowledge in the field has been accumulated and intensively discussed. Here, we attempted to organize the evidence "for" and "against" the hypothesized causal role of CS in aging. For that purpose, we utilized robust Koch-like logical criteria, based on the assumption that some quantitative relationships between the accumulation of senescent cells and aging rate should exist. If so, it could be expected that (i) the "CS load" would be greater in the premature aging phenotype and lesser in longevity phenotype; (ii) CS would promote age-related diseases, and (iii) the interventions that modulate the levels of senescent cells should also modulate health/lifespan. The analysis shows that CS can be considered a causal factor of aging and an important player in various age-related diseases, though its contribution may greatly vary across species. While the relative impact of senescent cells to aging could overall be rather limited and their elimination is hardly expected to be the "fountain of youth", the potential benefits of the senolytic strategy seems a promising option in combating age-related diseases and extending healthspan.