Modulation of Ionizing Radiation-Induced Apoptosis by Taurine in Human Peripheral Blood Lymphocytes: Flow Cytometry-based Quantification

Abstract

Background: Radiotherapy, a highly effective method of radiation-based treating cancers, can reduce the size of tumors and affect healthy tissues. Radiation-induced lymphopenia as a side effect of radiation therapy can reduce the effectiveness of the treatment.

Objective: This study aimed to examine how taurine can protect peripheral blood lymphocytes from radiation-based apoptosis.

Material and methods: In this experimental study, the effects of the taurine on lymphocytes were studied, and blood samples were divided into three groups: a negative control group that was not treated, a positive control group that was treated with cysteine (100 μg/ml), and a group that was treated with taurine (100 µg. mL^-1) in three different doses (4, 8 & 12 Gy) before irradiation. The percentage of apoptotic and necrotic lymphocytes was measured using flow cytometry 48 and 72 hours after the irradiation, respectively.

Results: According to the groups treated with taurine, the number of lymphocytes undergoing apoptosis was lower and higher compared to the negative and positive control groups, respectively. The decrease in this value was more pronounced 48 hours after radiation compared to 72 hours. Furthermore, there was a slight increase in the number of apoptotic lymphocytes with increasing radiation dose.

Conclusion: Taurine effectively protects human peripheral blood lymphocytes from radiation-based apoptosis.

Keywords: Apoptosis; Flow Cytometry; Ionizing Radiation; Lymphocyte; Radioprotective; Taurine.

Figure 1

The scavenging effect of different concentrations of Taurine (...) & cysteine (---) on DPPH radical at 517 nm. The number of examined samples in each engagement is equal to 3. Dots have covered the standard deviations due to their small magnitude. (DPPH: 2-diphenyl-1-picrylhydrazyl, RSA: free radical-scavenging activity)

Figure 2

Different Taurine concentrations (25-1000 mM) affect lymphocyte viability after 24, 48, & 72 hours of incubation using MTT assay. Data are expressed as the means of eight replicate experiments with error bars. *P≤0.005 compared to controls (untreated groups) (MMT: 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide)

Figure 3

Effect of Taurine on radiation-induced apoptosis in lymphocytes & comparison with controls after 48 hours post-radiation. The percentages of apoptotic lymphocytes are depicted as a histogram with standard deviations at three doses of 4, 8, & 12 Gy for four sample groups: non-irradiated & untreated, untreated with irradiation (negative control), cysteine-treated with irradiation (100 µg. mL^-1; positive control), & Taurine -treated with irradiation (100 µg. mL^-1)

Figure 4

Effect of Taurine on radiation-induced apoptosis in lymphocytes & comparison with controls after 72 hours post-radiation. The percentages of apoptotic lymphocytes are depicted as a histogram with standard deviations at three doses of 4, 8, & 12 Gy for four sample groups: non-irradiated & untreated, untreated with irradiation (negative control), cysteine-treated with irradiation (100 µg. mL^-1; positive control), & Taurine -treated with irradiation (100 µg. mL^-1)

Figure 5

The percentage of apoptotic lymphocytes as a function of dose & comparison of the presence or absence of Taurine (100 µg. mL^-1) & cysteine (100 µg. mL^-1) on the frequency of apoptosis induced by various doses of X-rays after 48 & 72 hours post-irradiation. Data are presented as mean values with standard errors. Background values (non-irradiated & untreated samples) are subtracted from each point shown on the graph.

Figure 6

Effect of Taurine & cysteine on radiation-induced apoptosis in lymphocytes as cytograms at three doses of 4, 8, & 12 Gy after 48 hours post-irradiation. Non-irradiated & untreated (A), untreated with irradiation (B, E & H), Taurine-treated with irradiation (C, F & I), & cysteine-treated with irradiation (D, G & J).

Figure 7

Effect of Taurine & cysteine on radiation-induced apoptosis in lymphocytes as cytograms at three doses of 4, 8, & 12 Gy after 72 hours post-irradiation. Non-irradiated & untreated (K), untreated with irradiation (L, P & S), Taurine-treated with irradiation (M, Q & T), & cysteine-treated with irradiation (N, R & V).