Tetramethylpyrazine Inhibits Retinal Apoptosis in Oxygen Induced Retinopathy

Abstract

Purpose: : To exploit the effect of Tetramethylpyrazine(TMP) on retinal apoptosis in oxygen induced retinopathy(OIR) mice.

Methods: : Fifty-four Neonatal C57BL/6 mice were randomly divided into 4 groups. Thirty-six postnatal day 7(P7) mice were exposed to 75±3% oxygen for 5 days and returned to room air to establish OIR model (Group 2-4). Eighteen mice were raised in room air as normoxia control (Group 1). TMP (intraperitoneal injection,200mg/Kg) was administered once a day from P7 to P11 (Group 3,n=6,sacrificed at P12) or from P12 to P16 (Group 4,n=12,sacrificed at P14 or P17). Normoxia control(Group 1) and hyperoxia control(Group 2) were injected with Normal Saline and sacrificed at P12,P14, P17. Serial sections of paraffin embedded mouse eye were cut sagittally per 3µm. To observe retinal apoptosis, TUNEL assay was used to measure on 6 sections per eye crossing the optic nerve.The interval between each section was 45µm. Sum of TUNEL-positive cells on each group eye were statistically analyzed by one-way ANOVA.

Results: : Group 1 didn’t show obvious TUNEL-positive cells. TUNEL-positive cells in Group 2 were mostly at P14 and mainly in the central inner nuclear layer, nearly 6 folds (P<0.0001) at P12 and 28 folds (P<0.0001) at P14, compared with Group 1. TMP decreased the apoptotic cells by 65.6% (P<0.0001) at P12 in Group 3 and 82.3%(P<0.0001) at P14 in Group 4, compared with Group 2. There were no significant differences among Group 1, 2, 4 at P17. The average numbers of retina apoptotic cells in 4 groups were in the table below and analyzed by one-way ANOVA (F=591.829, P<0.001).

Conclusions: : TMP inhibits retinal apoptosis in OIR and may have clinical utility to protect the hypoxic retina from degeneration, confirming that it may have potential value for the treatment of ischemic retinopathy.

Keywords: drug toxicity/drug effects • retinopathy of prematurity • apoptosis/cell death