Flow-cytometric analysis on cytotoxic effect of thimerosal, a preservative in vaccines, on lymphocytes dissociated from rat thymic glands

Effects of Treadmill Exercise on the Expression Level of BAX, BAD, BCL-2, BCL-XL, TFAM, and PGC-1α in the Hippocampus of Thimerosal-Treated Rats

Thimerosal (THIM) induces neurotoxic changes including neuronal death and releases apoptosis inducing factors from mitochondria to cytosol. THIM alters the expression level of factors involved in apoptosis. On the other hand, the anti-apoptotic effects of exercise have been reported. In this study, we aimed to discover the effect of three protocols of treadmill exercise on the expression level of mitochondrial transcription factor A (TFAM), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), BCL-2-associated death (BAD), BCL-2-associated X (BAX), BCL-XL, and BCL-2 (a pro-survival BCL-2 protein) in the hippocampus of control and THIM-exposed rats. Male Wistar rats were used in this research. Real-time PCR was applied to assess genes expression. The results showed that THIM increased the expression of pro-apoptotic factors (BAD and BAX), decreased the expression of anti-apoptotic factors (BCL-2 and BCL-XL), and decreased the expression of factors involved in mitochondrial biogenesis (TFAM and PGC-1α). Treadmill exercise protocols reversed the effect of THIM on all genes. In addition, treadmill exercise protocols decreased the expression of BAD and BAX, increased the expression of BCL-2, and increased the expression of TFAM and PGC-1α in control rats. In conclusion, THIM induced a pro-apoptotic effect and disturbed mitochondrial biogenesis and stability, whereas treadmill exercise reversed these effects.

Administration of thimerosal to infant rats increases overflow of glutamate and aspartate in the prefrontal cortex: protective role of dehydroepiandrosterone sulfate

Thimerosal, a mercury-containing vaccine preservative, is a suspected factor in the etiology of neurodevelopmental disorders. We previously showed that its administration to infant rats causes behavioral, neurochemical and neuropathological abnormalities similar to those present in autism. Here we examined, using microdialysis, the effect of thimerosal on extracellular levels of neuroactive amino acids in the rat prefrontal cortex (PFC). Thimerosal administration (4 injections, i.m., 240 μg Hg/kg on postnatal days 7, 9, 11, 15) induced lasting changes in amino acid overflow: an increase of glutamate and aspartate accompanied by a decrease of glycine and alanine; measured 10-14 weeks after the injections. Four injections of thimerosal at a dose of 12.5 μg Hg/kg did not alter glutamate and aspartate concentrations at microdialysis time (but based on thimerosal pharmacokinetics, could have been effective soon after its injection). Application of thimerosal to the PFC in perfusion fluid evoked a rapid increase of glutamate overflow. Coadministration of the neurosteroid, dehydroepiandrosterone sulfate (DHEAS; 80 mg/kg; i.p.) prevented the thimerosal effect on glutamate and aspartate; the steroid alone had no influence on these amino acids. Coapplication of DHEAS with thimerosal in perfusion fluid also blocked the acute action of thimerosal on glutamate. In contrast, DHEAS alone reduced overflow of glycine and alanine, somewhat potentiating the thimerosal effect on these amino acids. Since excessive accumulation of extracellular glutamate is linked with excitotoxicity, our data imply that neonatal exposure to thimerosal-containing vaccines might induce excitotoxic brain injuries, leading to neurodevelopmental disorders. DHEAS may partially protect against mercurials-induced neurotoxicity.

Use of whole-blood samples in in-house bulk and single-cell antigen-specific gamma interferon assays for surveillance of Mycobacterium tuberculosis infections

Tests based on the gamma interferon (IFN-gamma) assay (IGA) are used as adjunctive tools for the diagnosis of Mycobacterium tuberculosis infection. Here we compared in-house and commercial whole-blood IGAs to identify a suitable assay for the surveillance of tuberculosis in population studies. The IGAs were selected on the basis of the ease with which they are performed and because they require a small amount of a biological sample and do not require cell purification. Since a "gold standard" for latently M. tuberculosis-infected individuals is not available, the sensitivities and the specificities of the IGAs were determined with samples from patients with clinically diagnosed active tuberculosis and in Mycobacterium bovis BCG-unvaccinated healthy controls. The in-house tests consisted of a bulk assay based on diluted whole blood and a single-cell assay based on IFN-gamma intracellular staining. The commercial assays used were the QuantiFERON-TB-Gold (Q-TB) and the Q-TB in-tube tests. When the purified protein derivative was used as the antigen, in-house whole-blood intracellular staining was found to be highly discriminatory between active tuberculosis patients and BCG-vaccinated healthy controls, whereas the other IGAs did not discriminate between the two categories of patients. When M. tuberculosis-specific antigens were used, a very strong agreement between the results of the Q-TB in-tube assay and the clinical diagnosis was observed, while the Q-TB assay, performed according to the manufacturer's instructions, showed a significantly lower performance. Intriguingly, when the test was performed with RD1 proteins instead of peptides, its sensitivity was significantly increased. The in-house assay with diluted whole blood showed an elevated sensitivity and an elevated specificity, and the results agreed with the clinical diagnosis. Considering that the in-house assay uses 1/20 of the sample compared with the amount of sample used in the commercial IGA, it appears to be particularly promising for use in pediatric studies. Overall, the different assays showed different performance characteristics that need to be considered for surveillance of tuberculosis in population studies.

Thimerosal-induced apoptosis in human SCM1 gastric cancer cells: activation of p38 MAP kinase and caspase-3 pathways without involvement of [Ca2+]i elevation

Thimerosal is a mercury-containing preservative in some vaccines. The effect of thimerosal on human gastric cancer cells is unknown. This study shows that in cultured human gastric cancer cells (SCM1), thimerosal reduced cell viability in a concentration- and time-dependent manner. Thimerosal caused apoptosis as assessed by propidium iodide-stained cells and caspase-3 activation. Although immunoblotting data revealed that thimerosal could activate the phosphorylation of extracellular signal-regulated kinase, c-Jun NH2-terminal protein kinase, and p38 mitogen-activated protein kinase (p38 MAPK), only SB203580 (a p38 MAPK inhibitor) partially prevented cells from apoptosis. Thimerosal also induced [Ca2+](i) increases via Ca2+ influx from the extracellular space. However, pretreatment with (bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetate)/AM, a Ca2+ chelator, to prevent thimerosal-induced [Ca2+](i) increases did not protect cells from death. The results suggest that in SCM1 cells, thimerosal caused Ca2+-independent apoptosis via phosphorylating p38 MAPK resulting in caspase-3 activation.

Thimerosal-Induced Limbal Stem Cell Failure: Report of a Case and Review of the Literature

PURPOSE

To report a case of unilateral total limbal stem cell (LSC) failure and corneal opacification secondary to thimerosal- and contact lens-induced ocular surface toxicity.

METHODS

Interventional case report and review of the literature on thimerosal-induced ocular surface changes.

RESULTS

A 49-year-old woman with a 2-year history of long-term soft contact lens wear developed unilateral total LSC failure and corneal opacification secondary to presumed thimerosal-induced toxicity and contact lens wear. At presentation, best-corrected visual acuities were 20/120 in the right eye and 20/15 in the left eye. The patient underwent a keratolimbal allograft and amniotic membrane graft followed by a penetrating keratoplasty. At the last follow-up, the right eye showed a clear corneal graft with a best-corrected visual acuity of 20/30.

CONCLUSIONS

Thimerosal toxicity can lead to total LSC failure with secondary corneal vascularization and opacification. Keratolimbal allograft followed by penetrating keratoplasty can be successful in reconstructing the ocular surface in such cases.

Clotrimazole, an antifungal drug possessing diverse actions, increases the vulnerability to cadmium in lymphocytes dissociated from rat thymus

Since clotrimazole, known as an antifungal drug, exerts diverse actions on cellular functions, it is expected that clotrimazole can be used for other purposes. This antifungal drug protects the cells overloaded with Ca(2+) by A23187, a calcium ionophore. Therefore, the agent may prevent the cells from death induced by heavy metals such as CdCl(2), PbCl(2), or HgCl(2) that are respectively proposed to increase intracellular Ca(2+) concentration. To test this possibility, we have examined the effect of clotrimazole on the cells simultaneously treated with CdCl(2), PbCl(2), or HgCl(2) using rat thymocytes and a flow cytometer with fluorescent probes. The simultaneous application of clotrimazole and CdCl(2) significantly decreased cell viability, even though the concentrations of both were ineffective at affecting the viability. The significant decrease in cell viability was not due to the inhibition of Ca(2+)-ATPase and Ca(2+)-dependent K(+) channels that were induced by clotrimazole. The simultaneous application increased the population of cells with phosphatidylserine exposed on membrane surface, indicating the change in asymmetrical distribution of membrane phospholipids. Furthermore, the cytotoxicity induced by the combination of clotrimazole and CdCl(2) under nominally Ca(2+)-free condition was more profound than that under normal Ca(2+) condition. Therefore, the membrane may be a target for the cytotoxic action of clotrimazole and CdCl(2) that were simultaneously applied. It is also the case for PbCl(2), but not the case for HgCl(2). It is concluded that clotrimazole can modulate the cytotoxicity of some heavy metals.

Thimerosal Induces Apoptosis in a Neuroblastoma Model via the cJun N-Terminal Kinase Pathway

The cJun N-terminal kinase (JNK)-signaling pathway is activated in response to a variety of stimuli, including environmental insults, and has been implicated in neuronal apoptosis. In this study, we investigated the role that the JNK pathway plays in neurotoxicity caused by thimerosal, an ethylmercury-containing preservative. SK-N-SH cells treated with thimerosal (0-10 microM) showed an increase in the phosphorylated (active) form of JNK and cJun with 5 and 10 microM thimerosal treatment at 2 and 4 h. To examine activator protein-1 (AP-1) transcription, cells were transfected with a pGL2 vector containing four AP-1 consensus sequences and then treated with thimerosal (0-2.5 microM) for 24 h. Luciferase studies showed an increase in AP-1 transcriptional activity upon thimerosal administration. To determine the components of the AP-1 complex, cells were transfected with a dominant negative to either cFos (A-Fos) or cJun (TAM67). Reporter analysis showed that TAM67, but not A-Fos, decreased AP-1 transcriptional activity, indicating a role for cJun in this pathway. To assess which components are essential to apoptosis, cells were treated with a cell-permeable JNK inhibitor II (SP600125) or transfected with TAM67, and the downstream effectors of apoptosis were analyzed. Cells pretreated with SP600125 showed decreases in activation of caspases 9 and 3, decreases in degradation of poly(ADP-ribose) polymerase (PARP), and decreased levels of proapoptotic Bim, in comparison to cells treated with thimerosal alone. However, cells transfected with TAM67 showed no changes in those same components. Taken together, these results indicate that thimerosal-induced neurotoxicity occurs through the JNK-signaling pathway, independent of cJun activation, leading ultimately to apoptotic cell death.