Epidermal growth factor is a potent inhibitor of renin secretion

Effects of Genistein on Common Kidney Diseases

Genistein is a naturally occurring phytoestrogen (soy or soybean products) that is classified as an isoflavone, and its structure is similar to that of endogenous estrogens; therefore, genistein can exert an estrogen-like effect via estrogen receptors. Additionally, genistein is a tyrosine kinase inhibitor, which enables it to block abnormal cell growth and proliferation signals through the inhibition of tyrosine kinase. Genistein is also an angiogenesis inhibitor and an antioxidant. Genistein has effects on kidney cells, some of the kidney’s physiological functions, and a variety of kidney diseases. First, genistein exerts a protective effect on normal cells by reducing the inflammatory response, inhibiting apoptosis, inhibiting oxidative stress, inhibiting remodeling, etc., but after cell injury, the protective effect of genistein decreases or even has the opposite effect. Second, genistein can regulate renin intake to maintain blood pressure balance, regulate calcium uptake to regulate Ca²⁺ and Pi balances, and reduce vasodilation to promote diuresis. Third, genistein has beneficial effects on a variety of kidney diseases (including acute kidney disease, kidney cancer, and different chronic kidney diseases), such as reducing symptoms, delaying disease progression, and improving prognosis. Therefore, this paper reviews animal and human studies on the protective effects of genistein on the kidney in vivo and in vitro to provide a reference for clinical research in the future.

[Paraneoplastic syndrome in renal cell carcinoma]

Renal cell carcinoma associated paraneoplastic symptoms include constitutional symptoms as well as specific metabolic and biochemical abnormalities. These are present in up to 40% of patients with renal cell carcinoma during the course of the disease. This report provides information on the most common manifestations and their therapy; some rare variants are also mentioned. The importance of paraneoplasia lies partly in the fact that paraneoplastic symptoms may be the precursor of either primary or recurrent disease. The presence of paraneoplastic manifestations does not necessarily imply a poor prognosis or metastatic disease.

Attenuation of tubular apoptosis by blockade of the renin-angiotensin system in diabetic Ren-2 rats

BACKGROUND

Tubular atrophy is a major feature of most renal diseases and is closely associated with loss of renal function. The present study sought to investigate tubular epithelial cell apoptosis in experimental diabetic nephropathy and to explore the role of pro-apoptotic [transforming growth factor-beta (TGF-beta) and anti-apoptotic growth factors [epidermal growth factor (EGF)]. The effects of renoprotective therapy with blockade of the renin-angiotensin system (RAS) also were examined.

METHODS

Six-week-old female Ren-2 rats were injected with streptozotocin (STZ) and maintained diabetic for 12 weeks. Further groups of diabetic rats were treated with the angiotensin-converting enzyme (ACE) inhibitor, perindopril, or the angiotensin II type 1 (AT1) receptor antagonist, valsartan, for 12 weeks.

RESULTS

Widespread apoptosis, identified immunohistochemically by single stranded DNA and TUNEL, was noted in the tubules of diabetic Ren-2 rats. These changes were associated with a 50% decrease in EGF expression and a twofold increase in TGF-beta1 mRNA. Treatment of diabetic Ren-2 rats with either valsartan (20 mg/kg/day) or perindopril (6 mg/kg/day) reduced apoptosis to control levels in association with supranormal levels of EGF mRNA (P < 0.01) and a reduction in TGF-beta1 gene expression (P < 0.05) to that of control rats.

CONCLUSIONS

Tubular apoptosis is a prominent feature of diabetic Ren-2 rats that is attenuated by blockade of the RAS in association with modulation of pro- and anti-apoptotic growth factor expression.

Renal cell carcinoma: a paradigm of lanthanic disease

Renal cell carcinoma is characterized by varied and sometimes obscure manifestations, which include unusual metastatic sites and paraneoplastic and vascular syndromes. In this review, uncommon metastatic sites and their clinical significance are discussed, particularly the thyroid, nasal structures, vagina, and gastrointestinal sites. Paraneoplastic syndromes appear to be related predominantly to cytokines or immunologic mechanisms. Vascular syndromes are related to the tendency of the tumor to spread by direct venous extension and to complications related to the vascularity of the tumor or its metastases. The recognition of unusual manifestations of renal cell carcinoma is important because these syndromes may lead to the diagnosis. Moreover, paraneoplastic syndromes and vascular findings may not indicate unresectability or incurability.

Hemodynamic effects of epidermal growth factor in conscious rats and monkeys

The therapeutic application of growth factors to human disease has become closer to reality with the advent of faster means of synthesizing these molecules and novel drug delivery strategies. Epidermal growth factor (EGF) belongs to a large family of molecules with the ability to modulate growth. Purified extracts of EGF have been used clinically to modulate gastrointestinal secretion of hormones and accelerate healing. EGF is also reported to have both vascular smooth muscle contractile and relaxing activity Cardiovascular studies were performed with the bioactive 48-amino acid fragment of human EGF in rodents and primates to determine the effects of EGF on blood pressure and heart rate in conscious animals. Intravenous infusion of EGF induced an initial pressor response in rats followed by a prolonged decrease in blood pressure. In contrast, in monkeys, EGF had dose-related blood pressure-lowering effects only; significant hypotension was observed at doses ranging from 3 to 300 microg/kg i.v. Hypotension was associated with modest tachycardia in both species. To our knowledge, this is the first report of hemodynamic effects of EGF in primates, and it clearly documents that the mitogenic role of growth factors such as EGF is but one aspect of their physiology.

Transferable circulating factors and epithelial sodium transport after unilateral nephrectomy in the rat

1. In order to investigate the role of circulating serum factors in the altered renal haemodynamics and enhanced renal tubular transport observed in renal growth, micropuncture experiments were performed on normal animals infused with 20% plasma derived from animals in whom unilateral nephrectomy had been performed 3 days previously. 2. When animals infused with plasma from uninephrectomized animals (NxP) were compared with those infused with control plasma, the former had a higher tubular fluid flow rate measured at both the late proximal (LP; 26.7 +/- 1.6 vs. 18.4 +/- 1.4 nl min-1; P < 0.001) and early distal (ED; 14.9 +/- 1.0 vs. 7.8 +/- 1.0 nl min-1; P < 0.0001) sites, which was reflected in the final urine flow rate (16.1 +/- 3.4 vs. 5.1 +/- 0.8 microliter min-1; P < 0.005). 3. The single nephron glomerular filtration rate (SNGFR) was higher in animals infused with NxP as determined from samples taken at the LP (45.8 +/- 2.8 vs. 35.7 +/- 2.3 nl min-1; P < 0.01) and at the ED (34.5 +/- 2.5 vs. 28.1 +/- 1.8 nl min-1; P = 0.05) sites. However, this increase was not reflected in the whole kidney GFR (1.04 +/- 0.06 vs. 0.89 +/- 0.06; P = 0.07), suggestive of a preferential increase in filtration in the outer cortical nephrons. 4. Tubular Na+ transport was higher in the animals infused with NxP as evidenced by a decrease in the fractional delivery of Na+ at the ED site (4.5 +/- 0.4 vs. 6.5 +/- 0.6% of the filtered load; P < 0.05). However, in the final urine there was a significant increase in the urinary sodium excretion in animals infused with NxP (0.67 +/- 0.14 vs. 0.29 +/- 0.09%; P < 0.05) indicating that natriuresis and probably diuresis was a result of inhibition of Na+ and water transport in the late distal tubule and collecting duct. 5. In conclusion, these experiments demonstrate that circulating factors induced by a reduction in renal mass significantly alter glomerular filtration and tubular Na+ transport.

Modification of immunoreactive EGF and EGF receptor after acute tubular necrosis induced by tobramycin or cisplatin

Acute tubular necrosis induced by aminoglycoside antibiotics and various other nephrotoxins is followed by a regenerative process which leads to the restoration of damaged tubules. Several lines of evidence indicate that tubular regeneration is mediated by polypeptide growth factors such as epidermal growth factor (EGF). Previous studies devoted to cisplatin nephrotoxicity have shown that this agent causes tubular cystic degeneration possibly related to an impairment of renal tissue repair. Thus, we examined on a comparative basis the time course of the regenerative response subsequent to tubular damage induced by tobramycin or cisplatin, particular attention being paid to renal EGF and its receptor. Female Sprague-Dawley rats (160-180 g body weight) were treated during 4 consecutive days with daily doses of 200 mg/kg tobramycin i.p. (BID) or 2 mg/kg cisplatin (once a day). Sham-treated rats were given 0.9% NaCl i.p. following the same protocol. Groups of experimental animals (n = 5-10) were terminated at increasing time intervals (1, 4, 7, 14, 21, 60 days) after cessation of treatment. One hour prior to sacrifice, each individual received i.p. 200 mg/kg 5-bromo-2'-deoxyuridine (BrdU) for the immunohistochemical demonstration of cell proliferation. Blood was collected at the time of sacrifice in order to assess glomerular filtration rate by measuring serum creatinine and BUN levels. Kidneys were analyzed with respect to total EGF determined by RIA in renal tissue homogenates, and soluble EGF was assayed in extracts prepared by centrifugation. Renal tissue was processed for the immunohistochemical detection of S-phase cells, of EGF, of EGF receptors, and of the intermediate filament vimentin, the latter being used as a marker of epithelium dedifferentiation. In absence of nephrotoxic alterations, EGF was immunolocalized in distal tubules, whereas EGF receptor immunostaining was seen in proximal tubules cells. Vimentin immunostaining was confined to glomeruli and blood vessels. Tobramycin and cisplatin caused acute tubular necrosis in proximal convoluted tubules and proximal straight tubules, respectively. Tissue damage was accompanied by renal dysfunction reflected by an elevation of serum creatinine and BUN levels. Tubular necrosis was followed by a proliferative response indicative of tubular regeneration. Regenerative hyperplasia was associated with a reduction of total immunoreactive EGF due to a decrease of tissue-bound proEGF. Tubules undergoing regenerative repair were characterized by a disappearance of EGF receptors and the presence of immunoreactive vimentin. In tobramycin-treated rats, renal dysfunction lasted for 4-7 days and was fully reversible, as indicated by the return of serum markers to normal values.