Assessment of the frequency of mutant (hprt-) T lymphocytes from peripheral blood of patients with Hashimoto's thyroiditis

Molecular characterization of hypoxanthine guanine phosphoribosyltransferase mutant T cells in human blood: The concept of surrogate selection for immunologically relevant cells

Somatic cell gene mutations arise in vivo due to replication errors during DNA synthesis occurring spontaneously during normal DNA synthesis or as a result of replication on a DNA template damaged by endogenous or exogenous mutagens. In principle, changes in the frequencies of mutant cells in vivo in humans reflect changes in exposures to exogenous or endogenous DNA damaging insults, other factors being equal. It is becoming increasingly evident however, that somatic mutations in humans have a far greater range of interpretations. For example, mutations in lymphocytes provide invaluable probes for in vivo cellular and molecular processes, providing identification of clonal amplifications of these cells in autoimmune and infectious diseases, transplantation recipients, paroxysmal nocturnal hemoglobinuria (PNH), and cancer. The assay for mutations of the X-chromosomal hypoxanthine guanine phosphoribosyltransferase (HPRT) gene has gained popular acceptance for this purpose since viable mutant cells can be recovered for molecular and other analyses. Although the major application of the HPRT T cell assay remains human population monitoring, the enrichment of activated T cells in the mutant fraction in individuals with ongoing immunological processes has demonstrated the utility of surrogate selection, a method that uses somatic mutation as a surrogate marker for the in vivo T cell proliferation that underlies immunological processes to investigate clinical disorders with immunological features. Studies encompassing a wide range of clinical conditions are reviewed. Despite the historical importance of the HPRT mutation system in validating surrogate selection, there are now additional mutational and other methods for identifying immunologically active T cells. These methods are reviewed and provide insights for strategies to extend surrogate selection in future studies.

Thyroid nodules and thyroid autoimmunity in the context of environmental pollution

Evidence suggests that in most industrialized countries autoimmune disorders, including chronic lymphocytic thyroiditis, are increasing. This increase parallels the one regarding differentiated thyroid cancer, the increment of which is mainly due to the papillary histotype. A number of studies have pointed to an association between chronic lymphocytic thyroiditis and differentiated thyroid cancer. The upward trend of these two thyroid diseases is sustained by certain environmental factors, such as polluting substances acting as endocrine disrupting chemicals. Herein we will review the experimental and clinical literature that highlights the effects of environmental and occupational exposure to polluting chemicals in the development of autoimmune thyroid disease or differentiated thyroid cancer. Stakeholders, starting from policymarkers, should become more sensitive to the consequences for the thyroid resulting from exposure to EDC. Indeed, the economic burden resulting from such consequences has not been quantified thus far.

Changed presentation of Hashimoto's thyroiditis in North-Eastern Sicily and Calabria (Southern Italy) based on a 31-year experience

OBJECTIVE

To quantify the yearly prevalence of Hashimoto's thyroiditis at our Division and evaluate changes in its clinical presentation over the period 1975-2005.

DESIGN

We have reviewed retrospectively the clinical records of patients admitted to a university hospital located in Messina, Sicily (Italy), from January 1, 1975, through December 31, 2005. This facility attracts patients from North-Eastern Sicily and most of Calabria, the Italian region across the Straits. HT was diagnosed based on various combinations of clinical, laboratory, and instrumental findings. The study group consisted of 4064 HT patients diagnosed during these 31 years.

MAIN OUTCOME

We evaluated these indexes on a yearly basis: number of new HT diagnoses; age at presentation; male-to-female ratio; functional status; goitrous or nongoitrous variants with or without nodule(s); above-normal titers or levels of serum thyroid autoantibodies (thyroglobulin antibodies and thyroperoxidase antibodies). Several indexes have changed over those 31 years. Particularly, HT has become 10 times more common than it was until the early 1990s and males are relatively more represented. Patients are relatively younger, with a nongoitrous thyroid; the rate of S-Hypo exceeds largely the rate of O-Hypo. Serum thyroid autoantibodies have become less frequently positive, and when positive, they are present at a lower concentration.

CONCLUSIONS

Only environmental changes, as opposed to genetic changes, can account for such alterations in the presentation of HT in our geographical area.

In vivo and in vitro effects of statins on lymphocytes in patients with Hashimoto's thyroiditis

BACKGROUND

Statins have apoptotic effects on many cell types. Hashimoto's thyroiditis (HT) is an autoimmune disease in which cell-mediated autoimmune mechanisms are pathogenetically involved.

OBJECTIVE

The aim of this study was to evaluate the in vivo effects of Simvastatin on thyroid function, lymphocyte subtypes and also to investigate the apoptotic effects of Simvastatin, Mevastatin, Pravastatin and Cerivastatin on lymphocytes from patients with HT.

METHODS

In the first part of the study, 11 patients with HT and subclinical hypothyroidism (SH) were given Simvastatin (20 mg/day) for 8 weeks. Ten patients with SH and HT served as the control group. No treatment was given to controls. Thyroid function, C-reactive protein (CRP) levels and lymphocyte subtypes of both groups were determined before the study and after 8 weeks. In the second part of the study, the apoptotic effects of statins on lymphocytes were evaluated in patients with HT (n = 10) and normal subjects (n = 10) in vitro. Apoptosis was investigated by using Annexin-V and propidium iodide. Lymphocytes from patients and controls were incubated with different concentrations of Simvastatin, Cerivastatin, Mevastatin and Pravastatin.

RESULTS

An increase in serum free tri-iodothyronine and free thyroxine levels and a decrease in TSH levels were observed (P < 0.05) with Simvastatin treatment. CD4+ cells and B lymphocytes increased whilst CD8+ cells, natural killer cells and activated T lymphocytes decreased significantly in the treatment group (P < 0.05). The CRP level of the group also decreased with Simvastatin but it did not reach significance (P = 0.057). None of parameters was found to be different from the baseline in the control group. In in vitro experiments, apoptosis was observed in CD3 + (both in CD8+ and CD4+ cells) with all statins in both patient and control samples. Mevalonate, which was used in experiments, reversed apoptosis in some but not all samples.

CONCLUSIONS

The results of this study suggested that Simvastatin is an immune modulatory agent and improves thyroid function in patients with HT. This effect is probably mediated via lymphocyte apoptosis as demonstrated with in vitro experiments and is not confined to Simvastatin since Mevastatin, Pravastatin and Cerivastatin also induced apoptosis in lymphocytes.