Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Marie Francoise Mukanyangezi, Lucie Podmolíková, Wurood Al Hydad, Gunnar Tobin, Daniel Giglio, Rasheed Ahmad.
Radiotherapy is an important therapeutic approach against cervical cancer but associated with adverse effects including vaginal fibrosis and dyspareunia. We here assessed the immunological and oxidative responses to cervical irradiation in an animal model for radiation-induced cervicitis. Rats were sedated and either exposed to 20 Gy of ionising radiation given by a linear accelerator or only sedated (controls) and euthanized 1–14 days later. The expressions of toll-like receptors (TLRs) and coupled intracellular pathways in the cervix were assessed with immunohistofluorescence and western blot. Expression of cytokines were analysed with the Bio-Plex Suspension Array System (Bio-Rad). We showed that TLRs 2–9 were expressed in the rat cervix and cervical irradiation induced up-regulation of TLR5, TRIF and NF-κB. In the irradiated cervical epithelium, TLR5 and TRIF were increased in concert with an up-regulation of oxidative stress (8-OHdG) and antioxidant enzymes (SOD-1 and catalase). G-CSF, M-CSF, IL-10, IL- 17A, IL-18 and RANTES expressions in the cervix decreased two weeks after cervical irradiation. In conclusion, the rat uterine cervix expresses the TLRs 2–9. Cervical irradiation induces immunological changes and oxidative stress, which could have importance in the development of adverse effects to radiotherapy.
Cervical cancer is the fourth most common cancer form among women . While earlier stages are treated with surgery, advanced stages of cervical cancer are normally treated with radiotherapy alone or in combination with chemotherapy. The understanding on what happens in the normal tissue surrounding the tumour of the cervix upon exposure of radiation is at present lacking. Radiotherapy may cause vaginal mucosal atrophy, elastosis, fibrosis and vaginal stenosis and as a consequence dyspareunia [2, 3]. While the immune system has been studied in other irradiated tissues such as the colon , the lung  and the urinary bladder , the immune system of the irradiated cervicovaginal tract has not been studied. Pattern recognition receptors (PRRs) are part of the innate immune system and respond to pathogen-associated molecular patterns (PAMPs), which are constituted of microbial pathogens, and damage-associated molecular patterns (DAMPs). Toll-like receptors (TLRs) are an important group of receptors among PRRs. TLRs are expressed in different tissues including the cervix and respond to the exposure of bacteria and viruses thereby activating an immunological response . Studies show that the cervix of the rabbit expresses TLRs 2, 3, 4, 5, 6, 8 and 10 . Activation of TLRs induces intracellular activation of myeloid differentiation primary response 88 (MyD88) and TIR-domain-containing adapter-inducing interferon-β (TRIF) and via transcriptional factors (e.g. NFκB) may induce cytokine release .
In our study we wondered how radiation affects the immunological system of the uterine cervix with focus on the expression of TLRs. The expression of TLRs (TLR1-9) in the female reproductive tract has been demonstrated in previous studies [7, 16–18]. It is also established that TLR stimulation may boost radiation-induced immune responses in cancer . However, knowledge about how radiation affects the expression of TLRs in the normal cervical tissue is at present lacking. The most apparent finding of our study was that cervical irradiation induced increases of TLR5 in the epithelium concomitant with changes in cervical levels of TLR adaptor molecules MyD88, TRIF and NF-κB. The cervical epithelium expressed TLRs 2–9, which indicates that the cervical epithelium may respond to a high number of PAMPs and DAMPs. In the epithelium, TLR4, TLR6 and TLR9 were more expressed than TLR2, TLR3, TLR5, TLR7 and TLR8. Previous studies on cervical human epithelial cell lines showed the presence of all TLRs (1–9), where stimulation of TLR2, TLR3, TLR5 and TLR6 induced the release of cytokines . The myometrium expresses TLR2, TLR3 and TLR5 and stimulation of these TLRs may induce the release of pro-inflammatory and pro-labour mediators [21–23].
The present study shows that the rat uterine cervix expresses the TLRs 2–9. By exposing the rat cervix to radiation, TLR5 was activated together with an up-regulation of oxidative stress and antioxidative responses concomitant with a reduction in important pro-inflammatory cytokines.