M. Malatesta, C. Bertoni-Freddari, P. Fattoretti, B. Baldelli, S. Fakan, G. Gazzanelli

Ribonucleoprotein (RNP) containing structural constituents in hepatocyte nuclei of adult, old and adult, vitamin E-deficient rats were investigated to assess the effect of aging and increased oxidative stress on nuclear functions. Fibrillar centres (FCs), dense fibrillar (DFC) and granular (GC) components of nucleoli - sites of transcription and processing of ribosomal RNA - as well as perichromatin granules (PGs) - involved in intranuclear storage and transport of messenger RNA - in the nucleoplasm were preferentially evidenced by the ethylenediaminetetracetic acid (EDTA) method and measured by computer-assisted morphometric procedures. FCs size and the percentage of nucleolar surface occupied by FCs significantly decreased during aging and vitamin E-deficiency. The percentage of nucleolar surface occupied by GC and DFC remained unchanged in adult and old rats, but in vitamin E-deficient animals GC increased and DFC decreased significantly. PG density significantly changed in aging and vitamin E deficiency. In addition, immunocytochemical analyses were performed by using specific antibodies against transcription factors (polymerase II) and nucleoplasmic and nucleolar splicing factors (snRNPs, SC-35, fibrillarin). The intranuclear localisation of such factors was quite similar in adult, old and vitamin E-deficient rats. However, the quantitative evaluation of immunolabeling revealed that polymerase II and SC-35 significantly decreased in old and vitamin E-deficient rats in comparison to adult animals, while snRNPs and fibrillarin did not change between adult and old rats, but was significantly lower in vitamin E-deficient rats. Taken together, the present morphometric and immunocytochemical data indicate morphofunctional changes of nuclear constituents during aging and vitamin-E deficiency which could correlate with a decay of nuclear responsiveness to cellular metabolic needs. Considering the antioxidant action of alpha-tocopherol, our data lend further support to the importance of free radical production and control in the aging process.

Keywords (Optional): 
Vitamin E deficiency
oxidative stress