Botulinum Toxin Confers Radioprotection in Murine Salivary Glands

Abstract

Purpose-Xerostomia is a common radiation sequela, which has a negative impact on the quality of life of patients with head and neck cancer. Current treatment strategies offer only partial relief. Botulinum toxins (BTX) have been successfully used in treating a variety of radiation sequelae such as cystitis, proctitis, fibrosis, and facial pain. The purpose of this study was to evaluate the effect of BTX on radiation-induced salivary gland damage.Methods and Materials-We used a previously established model for murine salivary gland irradiation (IR). The submandibular glands (SMGs) of C5BL/6 mice (n=6/group) were injected with saline or BTX 72 hours before receiving 15 Gy of focal irradiation. Saliva flow was measured 3, 7, and 28 days after treatment. The SMGs were collected for immunohistochemistry, confocal microscopy, and Western blotting. A cytokine array consisting of 40 different mouse cytokines was used to evaluate cytokine profiles after radiation treatment.Results-Irradiated mice showed a 50% reduction in saliva flow after 3 days, whereas mice preinjected with BTX had 25% reduction in saliva flow (P<.05). Cell death detected by TUNEL staining was similar in SMG sections of both groups. However, neutrophil infiltrate, detected by myeloperoxidase staining, was 3-fold lower for the BTX treated mice. A cytokine array showed a 2-fold upregulation of LPS-induced chemokine (LIX/CXCL5) 3 days after IR. BTX pretreatment reduced LIX levels by 40%. At 4 weeks after IR, the saline (control) group showed a 40% reduction in basal SMG weight, compared with 20% in the BTX group. Histologically, BTXpretreated glands showed relative preservation of acinar structures after radiation.Conclusions-These data suggest that BTX pretreatment ameliorates radiation-induced saliva dysfunction. Moreover, we demonstrate a novel role for CXCL5 in the acute phase of salivary

Botox for the prevention of radiation‐induced Sialadenitis and xerostomia in head and neck cancer patients: A pilot study

“…This finding is consistent with a previous animal model in which salivary flow was reduced by 25% in Botox-treated glands compared with 50% in saline-treated glands up to 28 days after radiation exposure. 11 Salivary-related QOL as measured by OHIP-14 significantly decreased significantly in both groups after RT from V1 to V2 (p < 0.01) which is consistent with prior studies. This finding is likely due to the precipitous reduction in salivary output after RT.…”

“…CXCL-5, like CXCL-1, is a potent neutrophil chemoattractant produced after the acute stage of inflammation in response to IL-1 or TNF-α. 11 Further study is needed to determine the potential role of CXC biomarkers in radiation-induced sialadenitis, and the current findings must be interpreted with caution given the limited sample size and large number of tested inflammatory biomarkers.…”

“…Following RT, both groups experienced a 50% decrease in salivary flow following RT, which is consistent with prior studies. 11,28,29 The control group's salivary flow rate, however, continued to decrease causing a significant reduction from V1 to V3, whereas the Botox group's salivary flow remained relatively stable from V2 to V3, indicating potential preservation of salivary flow after the initial reduction. This finding is consistent with a previous animal model in which salivary flow was reduced by 25% in Botox-treated glands compared with 50% in saline-treated glands up to 28 days after radiation exposure.…”

“…8,9,21 Botox, as shown by its use in other inflammatory conditions, may likewise reduce the radiation-induced inflammatory cascade that leads to glandular fibrosis. [10][11][12][13]22,23 Furthermore, Botox improves QOL and lowers pain scores in patients with chronic orofacial pain, suggesting that it may reduce myofascial discomfort and improve QOL in patients undergoing head and neck RT. 24 None of the 20 patients enrolled in the study had an adverse event, indicating that Botox is potentially safe when combined with RT or concurrent chemoradiation.…”

“…10 A previous study in a rodent model showed that salivary Botox injection prior to RT reduced salivary gland inflammation and fibrosis. 11,12 In addition to its effects on blood flow, Botox has analgesic and anti-inflammatory effects which have been utilized to treat chronic inflammatory conditions such as arthritis and migraine disorders. 13 As a result, it is proposed that Botox may be able to prevent radiation-induced sialadenitis in HNC patients undergoing RT.…”