ABSTRACT
Objective To investigate the expression of Kuppel-like factor 2( KLF2 )after focal cerebral ischemia-reperfusion( I/R)injury in rats and the intervention effect of nuclear factor kappa B ( NF-κB)inhibitor. Methods Sixty healthy male SD rats were randomly divided into a sham operation group,an I/R group,and a NF-κB inhibitor group( n=20 in each group). A focal cerebral I/R model was induced by the intraluminal suture method,and NF-κB inhibitor( pyrrolidinedithio carbamate,PDTC)was given to intervene. The observation time points were 6,12,24,and 48 hours after I/R. Reverse transcription-polymerase chain reaction(PCR)and Western blot were used to measure KLF2 mRNA and protein expression in ischemic brain tissue. Enzyme-linked immunosorbent assay(ELISA)was used to detect the levels of serum tumor necrosis factorα( TNF-α),and they were compared among groups. Results Compared with the sham operation group,the expression levels of KLF2 mRNA and protein in I/R group in the ischemic brain tissue at each time point were averagely decreased( the relative expression levels of KLF2 mRNA:0. 46 ± 0. 03 vs. 0. 82 ± 0. 04,0. 30 ± 0. 04 vs. 0. 78 ± 0. 05,0. 18 ± 0. 04 vs. 0. 76 ± 0. 02,0. 26 ± 0. 02 vs. 0. 81 ± 0. 04,respectively;the relative expression levels of KLF2 protein:0. 46 ± 0. 04 vs. 0. 80 ± 0. 02,0. 30 ± 0. 02 vs. 0. 79 ± 0. 02,0. 15 ± 0. 02 vs. 0. 77 ± 0. 01,0. 24 ± 0. 01 vs. 0. 79 ± 0. 02,respectively). They reached the lowest values at 24 hours after I/R,while the serum TNF-αlevels were increased. There were significant differences(all P<0. 05). After giving NF-κB inhibitor PDTC,the expression levels of KLF2 mRNA and protein at 6,12,24,and 48 hours after I/R were upregulated differently compared with the I/R group. The relative expression levels of KLF2 mRNA were 0. 61 ± 0. 04,0. 44 ± 0. 03,0. 34 ± 0. 02,and 0. 43 ± 0. 04, respectively. Those of KLF2 protein were 0. 60 ± 0. 02,0. 43 ± 0. 02,0. 33 ± 0. 01,and 0. 44 ± 0. 03, respectively,while the levels of TNF-αwere decreased. There were significant differences(all P<0. 05). There was a negative correlation between the KLF2 mRNA levels and the serum TNF-αlevels at each time point in the I/R group and the PDTC group( r= —0. 728 ,P<0. 05 ). Conclusions The expression levels of KLF2 mRNA in brain tissue are decreased after I/R,and it is negatively correlated with the serum TNF-α levels. It may be involved in the pathological process of I/R by NF-κB pathway mediated inflammatory reaction.
ABSTRACT
Objective To investigate protective effects of thrombopoietin ( TPO) on cerebral model control in rats and associated signal transduction pathway. Methods Thread embolism was performed to generate cerebral ischemia-reperfusion rat model. Eighty male SD rats were randomly divided into sham operation group, model control group, TPO group, TPO and Janus kinase 2 ( JAK2 ) kinase inhibitor ( AG490 ) group. Before 30 min of ischemia-reperfusion, TPO group was given TPO (5 μg·kg-1) by intraperitoneal injection, TPO + AG490 group was given TPO (5 μg·kg-1) before 30 min of ischemia reperfusion, then given AG490 (8 μg·kg-1), and model control group were given the same dose of 0. 9% sodium chloride solution. The observation time points were 6, 12, 24, and 48 h after ischemia reperfusion. Immunohistochemical staining and Western blotting were used to measure the protein levels of Bcl-2, JAK2 and signal transducer & activator of transcription (STAT3). TdT-mediated dUTP nick end labeling (TUNEL) was used to detect apoptosis. Results Compared with model control group, the number of apoptotic cells were significantly reduced [(67. 50±9. 37) vs. (40. 20±7. 47)], the expression levels of Bcl-2, JAK2 and STAT3 protein were significantly increased [(35. 40±7. 39) vs. (78. 70±9. 75);(35. 68±6. 75) vs. (62.35±7.53); (25.40±9.45) vs.(55.36±9.69), respectively] 24 h after ischeia reperfusion in the TPO group (all P<0. 05). Compared with the TPO group, the Bcl-2, JAK2 and STAT3 protein levels were significantly decreased in TPO and AG490 group [(78. 70±9. 75) vs. (55. 40±9. 35);(62. 35±7. 53) vs. (40. 68±5. 89); (55. 36±9. 69) vs. (30. 40±9. 39), respetively], and the number of apoptotic cells was significantly increased [(40. 20±7. 47) vs. (55. 23±7. 65)] (all P<0. 05). Conclusion TPO can inhibit cell apoptosis after ischemia-reperfusion injury, the mechanism might be related to the activation of JAK2/STAT3 signal transduction pathway through raising the expression of Bcl-2 gene.