The effects of high glucose concentration, angiotensin II and its blockers on the production of IL-6 and fibronectin in cultured human mesangial cells

Ko, Kyung Sik; Ihm, Chun Gyoo; Kim, Hee Jin; Lee, Tae Won; Kim, Myung Jae

Abstract

BACKGROUND: Diabetic nephropathy is a leading cause of end-stage renal disease and is charaterized by activation of some growth factors (e.g., angiotensin II, endotelin-1, IL-8, and TGF-beta) and deposition of extracellular matrix proteins. Both ACE inhibitors and AT1 receptor blockers partially prevent renal hypertrophy in diabetes. Recently, IL-6 is thought to act as an autocrine growth factor for the mesangial cells. Angiotensin II (Ang II) is one of the noninflammatory stimulators of IL-6 release from mesangial cells. IL-6 have been implicated in glomerulonephritis, including mesangioproliferative glomerulonephritis. IL-6 may be associated with renal damage, especially mesangioproliferative diabetic nephropathy. However, little is known about the pathogenetic relations between IL-6 and diabetic nephropathy.
METHODS
To evaluate the effects of high glucose concentration, Ang II and its blockers on IL-6 and fibronectin production, human mesangial cells were cultured in various conditions. Normal concentration (100 mg/dL) and high concentration of D-glucose (450 mg/dL), Ang II (10(-7)M), high glucose with Ang II, captopril (10(-6)M), and losartan (10(-6)M) were added. After 48 hours, IL-6 and fibronectin concentration in the supernatant were measured by ELISA method.
RESULTS
The effects of various conditions on the production of IL-6 and fibronectin in cultured human mesangial cells were as follows: 1. The concentration of IL-6 in the supernatant was significantly low in high glucose group (9.9+/-0.2 pg/mL) compared to that in control group (18.0+/-6.2 pg/mL) (p<0.05), and there was no difference in the supernatant concentration of fibronectin between the groups of high glucose and control. 2. The concentration of IL-6 in the supernatant of Ang II group (28.0+/-5.0 pg/mL) was significantly higher than that in control group (18.0+/-6.2 pg/mL) (p<0.05), and there was no difference in the supernatant concentration of fibronectin between the groups of Ang II and control. 3. In the supernatant of high glucose with Ang II group, the concentration of IL-6 (20.0+/-4.0 pg/mL) was significantly higher than that of high glucose group (9.9+/-0.2 pg/mL) (p<0.05), and the concentration of fibronectin (3,100+/-50 pg/mL) was significantly higher than that of control group (2,840+/-290 pg/mL) (p<0.05). 4. The concentration of IL-6 in the supernatant was significantly lowered after the addition of captopril (10.7+/-1.8 pg/mL) and losartan (9.3+/-2.4 pg/mL) in high glucose with Ang II group (20.0+/-4.0 pg/mL) (p<0.05). 5. The concentration of fibronectin was significantly lowered after the addition of captopril (2,640+/-30 pg/mL) and losartan (2,440+/-230 pg/mL) in high glucose with Ang II group (3,100+/-50 pg/mL) (p<0.05). 6. There was no difference in the concentration of supernatant IL-6 and fibronectin between the groups of captopril and losartan.
CONCLUSION
High glucose concentration decreases and Ang II increases the production of IL-6 by cultured human mesangial cells. Captopril and losartan decrease the production of IL-6 and fibronectin which have been stimulated by high glucose concentration and Ang II. These drugs may be useful in the treatment of renal disease, especially diabetic nephropathy, in which Ang II and high blood glucose are cooperative in the progression of nephropathy.