| Objective: Renal fibrosis is one of the major complications associated with the propagation of hypertension. Matrix metalloproteinases, which degrade extracellular matrix, play an important role in the pathophysiologic process of renal fibrosis. Their activities increased in renal fibrotic diseases. This situation also exits in renal sclerotic lesion of hypertension. Doxycycline, which is one of the broad-spctrum matrix metalloproteinases inhibitors, can inhibit the activities of matrix metalloproteinases efficiently. Doxycycline inhibits a broad range of MMPs by proposed mechanisms that include transcriptional inhibition and a direct effect by coordination with the catalytic site. In view of many antihypertension drugs can improve renal function and degrade the activity of MMPs at the same time, we assumed whether or not doxycycline could delay the aggravation of hypertensive renal fibrosis and decrease the morbility and mortality of end-stage renal disease through its effects on inhibiting the activity of matrix metalloproteinase.The purpose of this research was to investigate the effect of doxycycline on renal MMPs in Stroke-Prone Spontaneously Hypertensive Rats, and to clarify whether it could delay interstitial fibrosis and ongoing renal function impairment caused by hypertension.Methods: 40 male SHR-SPs of 7 weeks old were randomly divided into 2 groups (n=20 for vehicle-treated group and doxycycline-treated group), 5 maleWistar-Kyoto rats (WKY) at the same age were used as normal controls. We treated SHR-SP chronically from the end of 7 weeks with doxycycline (30 mg-Kg^-day"1 in drinking water. The amount of drug was adjusted weekly by body weight) or vehicle. Throughout the intervention, body weight, indirect tail-cuff systolic blood pressure, urine volume, urinary protein, urinary creatinine were continuously measured. The intervention was terminated when mortality of vehicle-treated group reached 50%. Haemodynamics analysis was performed by Millar Mikro-Tip pressure transducer catheter in survival SHR-SPs. After the blood was collected to measure the plasma creatinine and urea nitrogen, kidneys were dissected and quickly frozen by liquid nitrogen and stored in -80 °C for further use. Some tissues were embedded in paraffin and sectioned for pathological analysis. The activity of MMP-2 and MMP-9 was detected by gelatin zymography and the activity of TIMP-1 and TIMP-2 was detected by reverse gelatin zymography, then quantitative analysis was performed by Image Pro Plus software, after scaned by scanning densitometer.Results:1. The haemodynamics analysis for survival SHR-SPs demonstrated that the value of +dp/dtmax and -dp/dtmin in doxycycline-treated group was higher than control animals (15410.1±1679.2 vs. 13684.1±1882.2mmHg/s and -10976.8±l 372.6 vs. -9429.6±1840.9mmHg/s,;?<0.05). Compared with control group, the SHR-SP received doxycycline had elevated tendency in systolic pressure and pulse pressure, whereas there was no statistical signifcance (the former 240.71 ±26.00 vs. 224.36±21.64mmHg, /? = 0.071, the latter 60.8±14.0 vs. 51.9±19.4 mmHg, p= 0.152) .2. Compared with WKY, the blood creatinine and urea nitrogen of SHR-SPs were markedly elevated (p<0.01). Although there was no differences of blood creatininebetween DOX group and CON group (32.67 ±8.71 vs. 27.83 ± 6.87nmmol/L, p= 0.129), SHR-SP received doxycycline had elevated tendency.3. At baseline, concentration of urinary protein, creatinine and ratio of protein/creatinine were of statistical differences in WKY and SHR-SP group. Higher protein excretion and lower creatinine excretion was observed in the SHR-SP. There was an obvious difference of protain/creatinine between DOX and CON from the age of 19 weeks (8.305 ±6.423 vs. 3.260 ±2.013 mg/umol, /X0.05), and the difference remained till the rest of the period.4. Both the kidney injury score and the collagen volume fraction of tubule were higher in DOX than CON (3.14 ±0.47 vs. 2.69 ±0.38 and 10.52 ±2.72% vs. 6.59 ± 1.85%,/K0.01), nevertheless there was no differences of glomerulus between the two groups (2.59±0.38 vs. 2.33±0.37 and 15.58±3.23% vs. 15.20±1.49%, /7>O.O5).5. MMPs activity in kidney by zymography demonstrated that the activity of MMP-2 and MMP-9 in SHR-SP was markedly increased compared with those of WKY. Between the two groups of SHR-SP, the activity of MMP-2 and MMP-9 expressed as fold changes with controls was lower in DOX group (proMMP-2: 3.26 ± 0.92 vs. 4.28 ± 0.59, Active MMP-2: 2.62± 0.75 vs. 3.39 ± 0.92, Total MMP-2: 2.75±0.67 vs. 3.58± 0.81;Active MMP-9: 2.89± 1.13 vs. 4.01 ±0.91;Total MMP-9: 2.53 ±0.89 vs. 3.18 ±0.71,/K0.05), except for proMMP-9.6. The activity of TIMP-1 and TIMP-2 by reverse gelatin zymography expressed as fold changes with controls was also higher in SHR-SP than those of WKY. Furthermore, the activity of these two inhibitors in doxycycline-treated group exceeded those of vehicle-treated group (TIMP-1: 2.89 ± 1.76 vs. 1.54± 0.86, /7 |
PDF Full Text Request