| Objective: In recent years, lots of studies shows, renal interstitial fibrosis is one of the common histopathological features of progressive renal disease of diverse etiology. The degree of renal interstitial fibrosis (RIF) has high relevance to that of renal dysfunction .So renal interstitial fibrosis could often been considered as a reliable indecator in evaluating progression of kidney diseases. Heme oxygenase-1(HO-1) is widely localized to microsome in a variety of mammalian cells .In the kidney, it mainly distributed the proximal and distal tubule in the renal cortex and medullary collecting duct epithelial cells.Recently a number of studies show that HO-1 possess important antioxidant, anti-inflammatory, antiapoptotic functions and improving microcirculation.So it is considered as a protective factor of kidney.Otterbein et al discovered that it could lower monocyte chemotactic protein 1(MCP-1) by inhibiting the nuclear factor kappa B(NF-κB) to protect the kidney from injury. A recent foreign study in vitro experiments show that the effect of protecting rat kidney from renal tubulointerstitial fibrosis may by increasing of inducing HO-1 and decreasing of transforming growth factor(TGF-β1).And a domestic research has reported the induction of HO-1 can also reduce significantly the damage of renal pathology in the chronic renal failure rats and delay the renal pathological changes in the 5/6 nephrectomized rats. However, little is known about the expression of HO-1 and its relation with TGF-β1, MCP-1 in the renal interstitial in the unilateral ureteral obstruction( UUO) model at home and abroad. This study investigate the renoprotective effects of HO-1 and its possible mechanism from the levels of cytokines by ureteral ligation resulting in renal interstitial fibrosis.Methods: 54 health male Wistar rats weighing 180~220g were randomly divided into 3 groups: sham-operated group (Group A, n=18), UUO group(Group B, n=18), UUO with hemin treated group(Group C, n=18). To establish the unilateral ureteral obstructive rat model, the left ureter was ligated by 4.0 silk at two points and cut between the ligatures under Chloral Hydrate anesthesia(0.1ml/Kg body wt,i.p). Sham-operated rats only free the ureter, but not ligated. Hemin (50μg/Kg/d) was administrated by daily gastric gavage with a single dose from one day before surgery, and the same volume of saline was administered for the controls. Rats were killed on days 3, 7 and 14 after surgery, and their left kidneys were promptly taken out .According to coronary place kidneys were cut with the longitudinal shape and half of them were fetched and were routinely fitted in 4% phosphate-buffered paraformaldehyde and paraffin embedded. Tissue sections at 5μm were obtained.Under the light microscope, pathological changes were observed by using HE and Masson stain to calclate the area of pathological changes. The changes of HO-1,MCP-1,TGF-β1 and their expression positions were analyzed by routine immunohistochemical method. The results were analyzed semi-quantitatively by the pathological image analysis system. All the data were analysed by SPSS 11.0 statistics software, P value<0.05 was considered to have statistical significance.Results: The rat kidneys in group A were normal like bean from the apperance.The obstruction kidneys become bigger as time went on in group B. The clear and transparent seeper was obstructed in the bigger kidneys.The renal cortex become thin, the renal pelvis expanded, minor calyx oppressed and become flat. There`s no abnormal changes in sham-operated group in the light microscrope using the staining mathods of HE and Masson. At the third day after the obstructive operation in group B, the renal tubles slightly expanded; there are a small number of monocyte/macrophage and lymphocyte inflamma- tory infiltration; the interstitial area was widened. At day 7, the renal tubles obviously expanded; degeneration, swelling and even necresis were seen in epthelial cells; there were a more monocyte/macrophage and lymphocyte inflammatory infiltr- ation; the interstitial area was even widened and epthelial cells became occasionally flatting. At day 14, above mentioned lesion aggravated; the tubule basement membrance appeared diffuse thicken , atrophy and even collapse;there were a lot of auantic tubules in the renal cortex and extra medulla; in the interstitial area there were more monocyte/macrophage and lymphocyte inflammatory infiltration and the interstitial area was wider than before;fibrorsis in the area also seemed more obvious than before.Using the staining mathods of Masson,at each time point interstitial lesion was significantly increased in the obstructed kidneys compared with that of group A(P<0.05), while the renal interstitial area in kidneys of group C significantly decreased compared with that of group B (P<0.05).The results of immunohistochemical staining are demonstrated as follow:the expression of HO-1, MCP-1 and TGF-β1 in the renal tubulointerstitium were at low level in group A; whereas in group B and group C, the expression of HO-1 was higher than those in group A and decreased gradually. And the level of HO-1 in group C was higher than that in group B at the same time point. In group B and group C the expression of MCP-1 was increased at day 3, peaked at day 7, and decresed at day 14.The level of MCP-1 in group C was lower than that in group B at the same time point and was obviously higher than those in group A. The expression of TGF-β1 increased gradually in group B and group C, and peaked at day 14. The level of TGF-β1 in group C was lower than that in group B at the same time point and obviously higher than that in group A. Rats in group B showed more significant pathological changes compared with those in group C. These three factors showed significant difference between any two of the three groups and between any two time points within a group (P<0.05), only rats in group A revealed constant levels in these three factors in different time points (p>0.05).Conclusion: Upregulation of HO -1 in the kidney may provide protection against UUO-mediated renal injury. The probable mechanism of the beneficial effect depends, at least in part, on HO-1 modulation of decreasing the expression of MCP-1 and TGF-β1. |
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