Effect Of Losartan On The Expression Of The TLR4 In Rats With Renal Ischemia-reperfusion Injury

Objective:To investigate the effect of Losartan on the expression of toll-like receptor4 (TLR4) and nuclear factor kappa Bp50 (NF-κBP50) in rats with renal ischemia-reperfusion injury (IRI), which might contribute to exploring the mechanisms of Losartan intervention in IRI protection.Method:Thirty-six healthy male wistar rats were randomly divided into three groups: Sham operation group (Sham group), Surgery group (Ir group), Losartan treatment group (Los group), with 12 rats in each group (n=12). Each group then was divided into two sub-groups depending on the time of sampling:6-hours group and 24-hours group, with 6 rats respectively (N= 6). The surgical protocols were as the following:For Sham group, the rats were incisied on their back of both sides of the spine, exposing both kidneys and renal pedic, separating renal arteries, but not cliping. For Ir group, the IRI animal model was made by clipping bilateral renal artery and restoring perfusion after 45 minutes. For Los group, Losartan gavage was given (80mg-kg-1-d-1) one week before surgery, with the other treatment same to Ir group. The pathological changes of renal tissue perfusion in different time point were observed by light microscope; the distribution and expression of TLR4, NF-kBp50 and IL-6 in Ischemic renal tissue were analysed by immunohistochemical technology and statistics.Results:1. The renal histomorphology was analysed by hematoxylin-eosin (HE) staining. As is in control, the tissue morphological structure in Sham group was clear, the renal tubular basement membrane was continuous, and there were no expansion in malpighian tube cavity, no hyperemia, edema and inflammatory cell infiltration in mesenchyme. In the Ir group, there were varying degrees of damage involving swelling, necrosis, disordered arrangement, tube cavity expansion, mesenchyme edema and inflammatory cell infiltration in the renal tubular epithelial cells. While these pathological damage was significantly alleviated in Los group compared with that in Ir group.2. The difference of serum Src values between 6h and 24h sub-group in Sham has no statistical significance (P>0.05). Compared with that in the Sham group, the serum Src value in Ir group was higher and peaked at 24 hours of IRI treatment. While the value was lower in Los group than that in Ir group, both at 6h and 24h time point (6h P<0.05,24h P<0.01), and higher than that in Sham grou (6h P<0.01, 24h P<0.01)3. Compared with that in the Sham group, the TLR4 protein levels in Ir group increased after 6 hours of IRI treatment and was mainly expressed in cytoplasm of renal tubule cell.24 hours later, the TLR4 protein was widely expressed besides renal tubule, with significant differences between these two sub-group (P<0.01). The TLR4 protein levels in Los group was lower than than that in Ir group (P<0.01), but was higher than that in Sham group (P<0.01).4. The NF-kB50 protein expressed lowly in kidney in Sham group, with no significant difference between 6h and 24h sub-group (P>0.05). In Ir group, the expression of NF-kB50 was upregulated after 6 hours of IRI treatment and obviously increased after 24 hours, comparing with that in Sham group ((P<0.01). The NF-kB50 protein levels in Los group was lower than than that in Ir group (P<0.01), but was higher than that in Sham group (P<0.01).5. The IL-6 expressed lowly in kidney in Sham group, with no significant Differentce between 6h and 24h sub-group (.P>0.05). In Ir group, the expression of IL-6 was upregulated after 6 hours of IRI treatment and obviously increased after 24 hours, comparing with that in Sham group (P<0.01). The IL-6 levels in Los group was lower than than that in Ir group (P<0.01), but was higher than that in Sham group (P<0.01).6.There is a significant correlation between the expression of TLR4 and NF-κBP50 (r=0.883,p<0.001) in Ir tissue and is also for TLR4 and IL-6 (r=0.914, p<0.001).Conclusion:1. The expression of TLR4, NF-κBP50 and IL-6 protein was gradually upregulat-ed after renal IRI, which indicated that RIRI could induce the inflammatory reaction after RIR by activating NF-κBP50 through TLR4 signal pathway.2. Losartan pretreatment can significantly reduce the pathological extent of renal tubular injury and the level of serum Scr, and down-regulate the expression of TLR4, NF-κBP50 and IL-6. Therefore, losartan could play a protectice role by inhibiting both TLR4 and NF-κB signaling pathways in renal ischemia reperfusion injury.