Role of connective tissue growth factor in experimental radiation nephropathy in rats

Radiation Nephropathy in a Nonhuman Primate Model of Partial-Body Irradiation With Minimal Bone Marrow Sparing-Part 2: Histopathology, Mediators, and Mechanisms

Male rhesus macaques were subjected to partial-body irradiation at 10, 11, or 12 Gy with 5% bone marrow protection. Animals were euthanized when dictated by prospectively determined clinical parameters or at approximately 180 d following irradiation. Histological sections of kidney were stained with hematoxylin and eosin as well as a battery of histochemical and immunohistochemical stains. Histopathological alterations were centered on glomerular changes and fibrosis of glomeruli and the interstitial compartment. These changes were first noted in animals necropsied approximately 100 d postirradiation and continued in animals necropsied through the observation period. Glomerular changes included congestion, thrombosis, erythrocyte degeneration, capillary tuft dilation, fibrin deposition, altered quantity and dispersion pattern of von Willebrand factor, increased mesangial matrix, and mesangial deposits of material that stained positively with periodic acid-Schiff staining. Areas of interstitial and glomerular fibrosis, as demonstrated by Masson's trichrome staining, were topographically associated with increased immunohistochemical staining for connective tissue growth factor, alpha smooth muscle actin, and collagen 1, but there was little staining for transforming growth factor beta. Fibrotic glomeruli had reduced microvascularity as demonstrated by reduced CD31 immunohistochemical staining. Vascular congestion was commonly noted in the region of the corticomedullary junction, and proteinaceous casts were commonly noted in cortical and medullary tubules. Longitudinal analysis of histopathological alterations provided evidence defining the latency, severity, and progression of delayed radiation-induced kidney injury.

Renoprotective effect of curcumin against the combined oxidative stress of diabetes and nicotine in rats

The progression of diabetic nephropathy (DN) is accelerated by smoking. The current study investigated the ability of curcumin to protect the kidneys against damage from oxidative stress induced by diabetes mellitus (DM) and nicotine (NC). A total of 24 male Wistar rats were divided into four groups of six rats each. DM was induced by a single intraperitoneal injection of streptozotocin 60 mg/kg body weight. DM rats were treated with or without NC in the absence or presence of curcumin for 8 weeks. As compared with the controls, DM rats exhibited reduced serum levels of high density lipoprotein, superoxide dismutase and glutathione peroxidase, and decreased renal mRNA expression levels of synaptopodin, connexin 43 and erythropoietin (EPO), which were further suppressed by NC and restored to normal levels by curcumin treatment. Additionally, DM rats exhibited increases in their lipid profiles (cholesterol, triacylglycerol and phospholipids), oxidative markers (malondialdehyde, γ-glutamyltranspeptidase and nitric oxide), kidney function markers (urea and creatinine) and the mRNA expression levels of vimentin, desmin, SREBP-1, iNOS and TGF-β1. These effects were further enhanced by NC, but counteracted by curcumin treatment. Kidneys from DM rats displayed glomerular hypertrophy, sclerosis and tubulo-interstitial changes represented by tubular lipid deposition, interstitial mononuclear cell infiltration and fibroplasia. Pancreatic islets exhibited cellular vacuolation, morphological irregularity and damaged or reduced in size β-cells. These renal and pancreatic changes became more severe following NC treatment and were ameliorated by curcumin. Therefore, NC-induced DN progression may predominantly operate by increasing oxidative stress, reducing the levels of antioxidants, suppressing EPO levels, and causing perturbations to gap junction and podocyte structure. Curcumin may ameliorate the damaging effects of DM and NC on the kidney through normalization of the mRNA expression levels of several genes important in the progression of DN.

Increased Expression of Connective Tissue Growth Factor (CTGF) in Multiple Organs After Exposure of Non-Human Primates (NHP) to Lethal Doses of Radiation

Exposure to sufficiently high doses of ionizing radiation is known to cause fibrosis in many different organs and tissues. Connective tissue growth factor (CTGF/CCN2), a member of the CCN family of matricellular proteins, plays an important role in the development of fibrosis in multiple organs. The aim of the present study was to quantify the gene and protein expression of CTGF in a variety of organs from non-human primates (NHP) that were previously exposed to potentially lethal doses of radiation. Tissues from non-irradiated NHP and NHP exposed to whole thoracic lung irradiation (WTLI) or partial-body irradiation with 5% bone marrow sparing (PBI/BM5) were examined by real-time quantitative reverse transcription PCR, western blot, and immunohistochemistry. Expression of CTGF was elevated in the lung tissues of NHP exposed to WTLI relative to the lung tissues of the non-irradiated NHP. Increased expression of CTGF was also observed in multiple organs from NHP exposed to PBI/BM5 compared to non-irradiated NHP; these included the lung, kidney, spleen, thymus, and liver. These irradiated organs also exhibited histological evidence of increased collagen deposition compared to the control tissues. There was significant correlation of CTGF expression with collagen deposition in the lung and spleen of NHP exposed to PBI/BM5. Significant correlations were observed between spleen and multiple organs on CTGF expression and collagen deposition, respectively, suggesting possible crosstalk between spleen and other organs. These data suggest that CTGF levels are increased in multiple organs after radiation exposure and that inflammatory cell infiltration may contribute to the elevated levels of CTGF in multiple organs.

Epigenetics in radiation-induced fibrosis

Radiotherapy is a major cancer treatment option but dose-limiting side effects such as late-onset fibrosis in the irradiated tissue severely impair quality of life in cancer survivors. Efforts to explain radiation-induced fibrosis, for example, by genetic variation remained largely inconclusive. Recently published molecular analyses on radiation response and fibrogenesis showed a prominent role of epigenetic gene regulation. This review summarizes the current knowledge on epigenetic modifications in fibrotic disease and radiation response, and it points out the important role for epigenetic mechanisms such as DNA methylation, microRNAs and histone modifications in the development of this disease. The synopsis illustrates the complexity of radiation-induced fibrosis and reveals the need for investigations to further unravel its molecular mechanisms. Importantly, epigenetic changes are long-term determinants of gene expression and can therefore support those mechanisms that induce and perpetuate fibrogenesis even in the absence of the initial damaging stimulus. Future work must comprise the interconnection of acute radiation response and long-lasting epigenetic effects in order to assess their role in late-onset radiation fibrosis. An improved understanding of the underlying biology is fundamental to better comprehend the origin of this disease and to improve both preventive and therapeutic strategies.

Genistein attenuates advanced glycation end product-induced expression of fibronectin and connective tissue growth factor

OBJECTIVE

To investigate the effect of advanced glycation end products (AGEs) on the expression of connective tissue growth factor (CTGF) and fibronectin (FN) in human peritoneal mesothelial cells (HPMC). To observe the effect of genistein (Gen) on the expression of CTGF and FN in HPMC induced by AGEs.

METHODS

First, HPMC were stimulated with different concentrations of AGEs (0, 200, 600 and 1,000 mg/l) for 48 h; the expression of FN was detected by reverse transcription-polymerase chain reaction (RT-PCR). Second, HPMC were divided into the following groups: (1) control group, (2) AGE-treated group (600 mg/l AGEs) and (3) Gen-treated groups with 600 mg/l AGEs and 25, 50 and 100 µMGen, respectively. The expression of messenger RNA (mRNA) for FN and CTGF was measured by RT-PCR; the expression of FN and CTGF protein was detected by enzyme-linked immunosorbent assay (ELISA) after 48 h.

RESULTS

The expression of FN mRNA in HPMC increased in a dose-dependent manner after induction with AGEs. Compared with controls, 600 mg/l AGEs markedly promoted the expression of mRNA and protein for FN and CTGF. Compared with the AGE-treated group (600 mg/l), 25, 50, and 100 µM Gen significantly inhibited the expression of mRNA and protein for FN and CTGF.

CONCLUSION

AGEs can markedly increase the expression of mRNA and protein for FN and CTGF; however, Gen can inhibit the expression of FN and CTGF mRNA and protein stimulated by AGEs, which implies that Gen probably decreases the accumulation of extracellular matrix through inhibiting the expression of CTGF, and it may play a role in anti-peritoneal fibrosis.

Renal expression of proto-oncogene Ets-1 on matrix remodeling in experimental diabetic nephropathy

The molecular mechanisms of glomerulosclerosis and tubulointerstitial fibrosis in diabetic nephropathy (DN) have received scant attention. Ets-1 proto-oncogene plays a role in matrix remodeling by regulating matrix-degrading enzymes. We investigated the possible role of Ets-1 in the pathogenesis of DN. 6-week-old male Sprague-Dawley rats were divided into two experimental groups as follows: control group (n=30) and a Diabetes mellitus group (n=40) induced by injection of streptozotozin (STZ). The rats were investigated at 1, 4, 8, 12 and 16 weeks after STZ-treatment. By means of immunohistochemistry, the expression of Ets-1 in glomeruli was significantly increased in STZ-treated rat kidneys from week 1 (P<0.05) and reached the peak at week 4 (P<0.05), followed by a downward trend at subsequent time points. Similarly, the expression of Ets-1 in the tubulointerstitium was also markedly increased from week 1 (P<0.05) and reached a maximum at week 8 (P<0.05). By double immunostaining, Ets-1-positive cells were frequently found to co-express matrix metalloproteinase-2 (MMP-2) in STZ-treated rat kidneys. Increased expression of tissue inhibitor of metalloproteinase-2 (TIMP-2) coincided with increased expression of α-smooth muscle actin (α-SMA) in STZ-induced DN. A positive relationship was observed between the expression of Ets-1 in glomeruli or tubulointerstitium and the expression of MMP-2 (P<0.01; P<0.01, respectively) in STZ-treated rat kidneys. The ratio of MMP-2 and TIMP-2 in glomeruli or tubulointerstitium was negatively correlated with deposition of type IV collagen (P<0.01; P<0.01, respectively). These findings suggest that Ets-1 may play a critical role in fine-tuning matrix remodeling of STZ-induced DN.

Correlation of clinical changes with regard to thyroxine replacement therapy in hypothyroid patients: focusing on the change of renal function

Thyroid dysfunction has an important role in renal insufficiency. The aim of the study was to correlate the change of renal function with other clinical factors after thyroxine therapy in hypothyroid patients. A prospective study was designed and 30 hypothyroid patients were included. All study subjects received 0.15-0.2 mg/day thyroxine for 12 weeks. Diastolic blood pressure and serum levels of creatine phosphokinase (CPK) and myoglobulin decreased significantly after thyroxine therapy. Serum creatinine decreased (0.87 ± 0.22 vs. 0.70 ± 0.17 mg/dl, p < 0.001) and estimated glomerular filtration rate (eGFR) increased significantly (82.06 ± 31.08 vs. 100.31 ± 31.79 ml/min/1.73 m(2); p < 0.001) after thyroxine replacement. Left ventricular ejection fraction (LVEF) was significantly increased after thyroxine replacement (64.47 ± 11.94 vs. 72.40 ± 13.89%, p = 0.026). No significant vascular functional changes of peripheral (pulse wave velocity) and renal interlobar arteries (pulsatility index and resistance index) were noted. The change of eGFR significantly correlated with the changes of serum-free T(4) (fT(4)), CPK, myoglobulin and LVEF. The correlation between the change of eGFR and thyroid-stimulating hormone (TSH) level was not significant. In conclusion, the GFR of hypothyroid patients increased significantly after thyroxine replacement. The change of GFR was significantly correlated with the changes of fT(4), CPK, myoglobulin and LVEF, but not with TSH.