Renal actions of dendroaspis natriuretic peptide in rabbits

Dendroaspis natriuretic peptide (DNP) is one of four members of the natriuretic peptide family sharing functional and structural properties. The purpose of the present study was to elucidate the physiological role of DNP on renal functions and its cellular mechanism in the rabbit kidney. DNP (5 μg/kg/min) infused intravenously increased urine volume and urinary excretion of electrolytes. These renal actions induced by DNP were more pronounced than those caused by atrial natriuretic peptide (ANP). We compared profiles of (125)I-ANP and (125)I-DNP by reverse-phase HPLC during incubation in rabbit plasma at 37°C for 1, 2, and 4h. While (125)I-ANP was quickly degraded within 1h, (125)I-DNP was still stable in plasma for 4h. DNP induced the greatest cyclic guanosine monophosphate (cGMP) production in the glomeruli in a dose-dependent manner, when compared to other renal structures including cortical tubules, outer medullary tubules, and inner medullary tubules. Affinity cross-linking analysis revealed NPR-A is selective receptor for DNP in glomeruli. Forskolin, a stimulator of adenylyl cyclase, significantly decreased cGMP production in the renal glomeruli but not in the renal medulla. In summary, DNP is a more effective activator of renal functions than ANP, possibly because of the degradation resistance of DNP against the endogenous peptidases in plasma or tissues. These findings suggest that DNP plays a pivotal role as a renal regulating peptide via specific natriuretic peptide receptors with a guanylyl cyclase domain.     

Molecular and cellular effects of Tamm-Horsfall protein mutations and their rescue by chemical chaperones

Correct folding of a nascent polypeptide in the lumen of the endoplasmic reticulum (ER) into a three-dimensional conformation is a crucial step in the stability, intracellular trafficking, and targeting to the final destination of a protein. By transiently and stably expressing human-relevant mutants of Tamm-Horsfall protein in polarized Madin-Darby canine kidney cells, we show here that a cysteine-altering mutation in the evolutionally conserved cysteine-rich domain had more severe defects in ER exit and surface translocation and triggered more apoptosis than a cysteine-altering mutation outside the domain. Both mutants were able to specifically bind and trap the wild-type Tamm-Horsfall protein (THP) and prevent it from exiting the ER and translocating to the cell surface. This explains at least partly why in patients with THP-associated diseases there is a marked urinary reduction of both the mutant and the wild-type THP. Exposure of mutant-expressing cells to low temperature (30 °C), osmolytes (glycerol, trimethylamine N-oxide, and dimethyl sulfoxide), and the Ca(2+)-ATP inhibitor thapsigargin only slightly relieved ER retention and increased surface targeting of the mutants. In contrast, sodium 4-phenylbutyrate and probenecid, the latter a uricosuric drug used clinically to treat gout, markedly reduced ER retention of the mutants and increased their surface translocation and secretion into the culture media. The rescue of the THP mutants was associated with the restoration of the level and subcellular localization of cytosolic chaperone HSP70. Our results reveal intricate mechanistic details that may underlie THP-associated diseases and suggest that novel therapeutics enhancing the refolding of THP mutants may be of important value in therapy.     

EGFR protein overexpression correlates with chromosome 7 polysomy and poor prognostic parameters in clear cell renal cell carcinoma

Background

The role of epidermal growth factor (EGF) and its receptor (EGFR) in the pathogenesis and progression of various malignant tumors has long been known, but there is still disagreement concerning prognostic significance of EGFR expression in clear cell renal cell carcinoma (CCRCC). The present study was designed to analyze more objectively the protein EGFR expression in CCRCC and to compare its value with EGFR gene copy number changes and clinicopathologic characteristics including patient survival.

Methods

The protein EGFR expression was analyzed immunohistochemically on 94 CCRCC, and gene copy number alterations of EGFR by FISH analysis on 41 CCRCC selected according to distinct membrane EGFR staining.

Results

Membrane EGFR expression in tumor cells was heterogeneous with respect to the proportion of positive cells and staining intensity. FISH analysis did not reveal EGFR gene amplification, while polysomy of chromosome 7 found in 41% was associated with higher EGFR membrane expression. Moreover, EGFR overexpression was associated with a higher nuclear grade, larger tumor size and shorter patient''s survival, while there was no connection with pathological stage.

Conclusion

In conclusion, the protein expression of EGFR had an impact on prognosis in patients with CCRCC, while an increased copy number of chromosome 7 could be the possible reason for EGFR protein overexpression in the absence of gene amplification.     

苯那普利对糖尿病大鼠肾小球MMP-9影响的实验研究

目的探讨苯那普利对糖尿病大鼠肾小球基质金属蛋白酶-9（MMP-9）表达的影响。方法将雄性SD大鼠30只,随机抽出10只动物作为正常对照组（C组）,其余20只采用腹腔注射STZ制备糖尿病大鼠模型。将这20只造模成功的糖尿病大鼠模型随机分为2组：糖尿病组（DM组）和药物处理组（DB组）。其中药物处理组即DB组大鼠每天应用苯那普利进行治疗性灌胃,C组和DM组用等量自来水灌胃。分别于治疗4、8周后,测定皿糖和内生肌苷清除率,用代谢笼收集24h尿量。利用免疫组织化学染色及图像分析方法,对MMP-9在肾组织不同时间点的含量变化进行定性分析。结果苯那普利治疗组血糖水平和内生肌苷清除率明显降低,与糖尿病模型组相比有显著性差异。免疫组织化学染色显示：MMP-9在正常肾小球有阳性表达;DM组大鼠病程第8周时,MMP-9在肾小球表达明显减弱;DB组大鼠病程第8周时,经苯那普利治疗后,与同期糖尿病组比较表达明显上调。图像分析方法定量分析免疫组织化学染色阳性面积百分比,苯那普利治疗后第4周和第8周糖尿病肾病的大鼠肾小球MMP-9的阳性面积百分比分别为25．55％±3．44％和20．10％±2．11％,与糖尿病组对比有明显的提高（P〈0．01）。结论MMP-9在糖尿病肾小球中的表达随病程进展逐渐减弱,苯那普利可能部分通过上调MMP-9在肾小球中的表达起到保护肾脏的作用。     

Correlation of low molecular weight advanced glycation end products and nitric oxide metabolites with chronic complications in type 1 diabetic patients

Advanced glycation end products (AGEs) are involved in the occurrence of vascular complications in diabetes. The present study was undertaken to investigate the level of low-molecular weight products of AGEs (LMW-AGEs) in relation to microvascular complications in type 1 diabetes, and the possible relationship with nitric oxide (NO) as a marker of endothelial function. Patients with normal renal function (NRF) were classified into two groups: (1) without, and (2) with diabetic neuropathy; and patients with renal impairment also into two groups: (3) diabetic renal disease, and (4) end-stage renal disease. The fluorescence of LMW-AGEs and measurement of NO metabolites was assessed in 277 serum samples. In addition, multiple regression analysis was performed. In group 1, LMW-AGEs level (9.3±1.1 AF%) was higher than in the control group (2.4±0.3 AF%). A trend in the increase of LMW-AGEs with neuropathy (29.7±5.5 AF%, group 2), and further with renal impairment (47.0±8.0, group 3 and 137.8±25.5 AF%, group 4), was observed. In multivariate regression analysis LMW-AGEs were associated with NO metabolites in group 2. In NRF patients, diabetic neuropathy was significantly correlated with LMW-AGEs and NO metabolites, independently of serum creatinine and duration of diabetes. This relationship suggests that the NO and LMW-AGEs’ actions (possibly synergistic) in endothelial activation possess a role in the initiation and development of diabetic microvascular complications.     

Activity of SU11248, a multitargeted inhibitor of vascular endothelial growth factor receptor and platelet-derived growth factor receptor, in patients with metastatic renal cell carcinoma and various other solid tumors

SU11248 sunitinib malate sutent^® is a selective inhibitor of certain protein tyrosine kinases including VEGF-R types 1–3 PDGF-R-a and -b, c-kit, and RET. Its antitumor activity may result from both inhibition of angiogenesis and direct antiprofilerative effects on certain tumor types. In several phase I/II/III studies, sutent^® was found to be effective as second and first line treatment in metastatic renal cell carcinoma (RCC). In fact, with a 37% response rate and an additional 48% stable disease sutent became the drug of choice for first line treatment in RCC. Sutent^® was also effective as second line treatment in patients with gastrointestinal stromal tumors (GIST) with 8% response rate, 70% stable disease and a 20-month median survival. Prolonged stable disease was also documented in neuroendocrine tumors. In addition, a phase II study in multitreated women with breast cancer, sutent^® demonstrated a moderate activity with 16% clinical benefit. Finally, in non-small cell lung cancer (NSCLC) in patients’ progressing on chemotherapy sutent^® was able to achieve a 10% response rate, a level of activity similar to those documented by other agents approved for lung cancer. The agent is being tested in other tumors with a modified schedule of dosage.     

实验性X综合征大鼠模型的建立

目的　建立一种典型的X综合症动物模型。方法　雄性SD大鼠施行两肾一夹术后普通饲料喂养 4周 ,诱发肾性高血压 ,继以高果糖饲料喂养 4周 ,诱导建立X综合症模型。结果　术后 4周 ,大鼠仅出现收缩压升高 ,血糖、血脂未见明显改变。高果糖饲料喂养 4周后 ,大鼠出现高血糖、高胰岛素血症、胰岛素抵抗、高血压和高脂血症。结论　肾性高血压形成后高果糖饮食 1个月 ,可诱导SD大鼠出现典型的X综合症 ,为研究胰岛素抵抗及其伴随的心血管疾病提供了一种理想的动物模型。