Risk of stroke with antivenom usage after venomous snakebite in Taiwan: a population-based cohort study

BACKGROUND AND PURPOSE

Stroke is a rare complication of snakebites, but may lead to serious sequelae. We aimed to explore the relationship between venomous snakebite and the risk for acute stroke, in a nationwide population-based cohort study.

METHODS

This retrospective cohort study used claims data between 1 January 2000 and 31 December 2012, from the Taiwan National Health Insurance Research Database. The study included data of patients aged 18 years or older with venomous snakebite (n = 535), matched for propensity score with controls without venomous snakebite (n = 2140). The follow-up period was the duration from the initial diagnosis of venomous snakebite and administration of antivenom to the date of an acute stroke, or until 31 December 2013. The competing risk model was used to estimate the hazard ratio (HR) and 95% confidence intervals (CIs) of stroke, ischemic stroke and hemorrhagic stroke, after adjusting for demographic and other possible stroke risk factors.

RESULTS

The adjusted HR for the venomous snakebite group compared with the control group was 2.68 for hemorrhagic stroke (95% CI = 1.35-5.33). Stratified analysis showed that the older age group (>65 years old) had a higher risk of hemorrhagic stroke. A 2.72-fold significant increase in the risk for hemorrhagic stroke was observed following venomous snakebite with antivenom usage (95% CI = 1.41-5.26).

CONCLUSION

Venomous snakebite is associated with an increased risk of hemorrhagic stroke after the use of antivenom. Further study of the underlying mechanism is warranted.

Nitric oxide improves cisplatin cytotoxicity in head and neck squamous cell carcinoma

OBJECTIVE

To test whether nitric oxide (NO) enhances the cytotoxicity of cisplatin in a head and neck squamous cell carcinoma (HNSCC) cell line.

BACKGROUND

Cisplatin is one of the most frequently used chemotherapeutic agents in the treatment of HNSCC. NO has been shown to play an important role in regulating tumor growth. Previous studies demonstrate that NO can enhance the cytotoxicity of cisplatin in Chinese hamster lung fibroblasts. In this report, we examined the in vitro interaction of NO and cisplatin in a HNSCC cell line.

MATERIALS AND METHODS

CCL23 cells were pretreated with three different NO donors: PAPA/NO (t 1/2 = 15 min), DPTA/NO (t 1/2 = 3 h), and DETA/NO (t 1/2 = 20 h). The cells were rinsed and exposed for 6 hours to a culture medium containing cisplatin. Cell survival and LD50 of cisplatin were calculated with and without NO pretreatment.

RESULTS

PAPA/NO and DPTA/NO did not show any cytotoxic activity and did not change the LD50 of cisplatin. DETA/NO when used alone resulted in 25.6% cell death at its peak dose (100 microM). Pretreatment with DETA/NO resulted in almost a threefold reduction of the LD50 of cisplatin (6.8 vs. 2.4 microg/mL). Pretreatment with DETA/NO sensitized the HNSCC cells to subsequent cisplatin activity (two-sided P =.00016).

CONCLUSION

Pretreatment of HNSCC cells with long-acting NO donors enhances cisplatin activity. Short- and medium-acting NO donors do not exert a toxic effect and do not augment the activity of cisplatin. NO agonists should be considered in the future as a possible adjunct to cisplatin in the treatment of HNSCC. Further studies with animal models are necessary to further clarify this relationship.

Antisense cyclin D1 enhances sensitivity of head and neck cancer cells to cisplatin

OBJECTIVES

Cyclin D1 is a cell cycle regulatory factor that modulates a critical step in cell cycle control. Cyclin D1 is overexpressed in a significant proportion of head and neck cancers and correlates with a poor prognosis. Abrogation of cyclin D1 action through antisense cyclin D1 shows promise as an antitumor therapy, with an inhibitory effect in head and neck squamous cell carcinoma both in vitro and in vivo. The suppressive effect of antisense cyclin D1 in head and neck cancer xenografts in nude mice is incomplete, however, suggesting that combination with another antitumor agent is necessary for complete tumor eradication. Cisplatin is a widely used chemotherapeutic agent in head and neck cancer, and is particularly effective in combination with radiation therapy. In this study, we investigate whether antisense cyclin D1 enhances the sensitivity of head and neck cancer cells to cisplatin. Such an enhancement of sensitivity would suggest that combination therapy using antisense cyclin D1 and cisplatin would be an effective treatment modality for head and neck cancer.

STUDY DESIGN

Antisense cyclin D1 was transfected into the head and neck squamous cell carcinoma cell line CCL23 using a plasmid vector. Both the parental CCL23 cells and the antisense cyclin D1-transfected CCL23 cells (CCL23AS) were treated with cisplatin at increasing concentrations. The dosage of cisplatin ranged from 1 microg/mL to 10 microg/mL. Initial exposure to cisplatin was for 2 hours, with increasing exposure times in succeeding experiments. Cell viability assays were done following cisplatin exposure. Dose response curves for the two cell lines were plotted and compared. Western blot analyses were done on the cisplatin-treated cell lines to determine levels of cyclin D1 expression.

RESULTS

Increasing concentrations of cisplatin resulted in significantly higher rates of cell killing in the antisense cyclin D1-transfected cells than in the parental cells. The ID50 values for the parental CCL23 cells and the antisense cyclin D1-transfected CCL23 cells were 7 microg/mL and 3 microg/mL, respectively, indicating significant enhancement of sensitivity to cisplatin in the antisense cyclin D1-transfected cells. Western blot analyses demonstrated decreased expression of cyclin D1 in the CCL23AS cells with increasing doses of cisplatin, compared with the parental CCL23 cells.

CONCLUSIONS

Antisense cyclin D1-transfected CCL23 cells demonstrate an enhanced sensitivity to the effects of cisplatin compared with the parental cell line. Although the mechanism for this phenomenon is not completely understood, the data suggests the potential use of combination therapy using antisense cyclin D1 and cisplatin for head and neck cancers. While neither agent alone can completely eradicate head and neck cancers, the synergistic effect of the two may be an effective therapeutic protocol for refractory head and neck cancers. Future investigation into the combination of antisense cyclin D1 with cisplatin for treatment of head and neck cancer is needed.