Renal thrombotic microangiopathy in mice with combined deletion of endocytic recycling regulators EHD3 and EHD4

Eps15 Homology Domain-containing 3 (EHD3), a member of the EHD protein family that regulates endocytic recycling, is the first protein reported to be specifically expressed in the glomerular endothelium in the kidney; therefore we generated Ehd3(-/-) mice and assessed renal development and pathology. Ehd3(-/-) animals showed no overt defects, and exhibited no proteinuria or glomerular pathology. However, as the expression of EHD4, a related family member, was elevated in the glomerular endothelium of Ehd3(-/-) mice and suggested functional compensation, we generated and analyzed Ehd3(-/-); Ehd4(-/-) mice. These mice were smaller, possessed smaller and paler kidneys, were proteinuric and died between 3-24 weeks of age. Detailed analyses of Ehd3(-/-); Ehd4(-/-) kidneys demonstrated thrombotic microangiopathy (TMA)-like glomerular lesions including thickening and duplication of glomerular basement membrane, endothelial swelling and loss of fenestrations. Other changes included segmental podocyte foot process effacement, mesangial interposition, and abnormal podocytic and mesangial marker expression. The glomerular lesions observed were strikingly similar to those seen in human pre-eclampsia and mouse models of reduced VEGF expression. As altered glomerular endothelial VEGFR2 expression and localization and increased apoptosis was observed in the absence of EHD3 and EHD4, we propose that EHD-mediated endocytic traffic of key surface receptors such as VEGFR2 is essential for physiological control of glomerular function. Furthermore, Ehd3(-/-); Ehd4(-/-) mice provide a unique model to elucidate mechanisms of glomerular endothelial injury which is observed in a wide variety of human renal and extra-renal diseases.     

The spectrum of renal thrombotic microangiopathy in lupus nephritis

Introduction

Among various lupus renal vascular changes, thrombotic microangiopathy (TMA) presented with the most severe clinical manifestations and high mortality. The pathogenesis of TMA in systemic lupus erythematosus (SLE) was complicated. The aim of this study was to assess clinical manifestations, laboratory characteristics, pathological features and risk factors for clinical outcomes of lupus nephritis patients co-existing with renal TMA in a large cohort in China.

Methods

Clinical and renal histopathological data of 148 patients with biopsy-proven lupus nephritis were retrospectively analyzed. Serum complement factor H, A Disintegrin and Metalloprotease with Thrombospondin type I repeats 13 (ADAMTS-13) activity, antiphospholipid antibodies and C4d deposition on renal vessels were further detected and analyzed.

Results

In the 148 patients with lupus nephritis, 36 patients were diagnosed as co-existing with renal TMA based on pathological diagnosis. Among the 36 TMA patients, their clinical diagnoses of renal TMA were as followings: 2 patients combining with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome, 2 patients combining with anti-phospholipid syndrome, 2 patients with malignant hypertension, 1 patient with scleroderma and the other 29 patients presenting with isolated renal TMA. Compared with the non-renal TMA group, patients with renal TMA had significantly higher urine protein (7.09 ± 4.64 vs. 4.75 ± 3.13 g/24h, P = 0.007) and serum creatinine (159, 86 to 215 vs. 81, 68 to 112 μmol/l, P <0.001), higher scores of total activity indices (AI) (P <0.001), endocapillary hypercellularity (P <0.001), subendothelial hyaline deposits (P = 0.003), interstitial inflammation (P = 0.005), glomerular leukocyte infiltration (P = 0.006), total chronicity indices (CI) (P = 0.033), tubular atrophy (P = 0.004) and interstitial fibrosis (P = 0.018). Patients with renal TMA presented with poorer renal outcome (P = 0.005) compared with the non-TMA group. Renal TMA (hazard ratio (HR): 2.772, 95% confidence interval: 1.009 to 7.617, P = 0.048) was an independent risk factor for renal outcome in patients with lupus nephritis. The renal outcome was poorer for those with both C4d deposition and decreased serum complement factor H in the TMA group (P = 0.007).

Conclusions

There were various causes of renal TMA in lupus nephritis. Complement over-activation via both classical and alternative pathways might play an important role in the pathogenesis of renal TMA in lupus nephritis.     

Pulmonary tumor thrombotic microangiopathy successfully treated with corticosteroids: a case report

Background

Pulmonary tumor thrombotic microangiopathy is a special type of tumor thromboembolism. We report the case of a patient who developed pulmonary tumor thrombotic microangiopathy with alveolar hemorrhage. Almost all patients with pulmonary tumor thrombotic microangiopathy die within 1 week of the onset of dyspnea; however, the prognosis in this case was better, with 10 weeks of survival from presentation.

Case presentation

A 62-year-old Japanese man was referred to our hospital with a 4-week history of dyspnea on exertion and severe pulmonary hypertension. Five years previously, he had undergone distal gastrectomy for gastric cancer. He was afebrile, normotensive, and hypoxemic. A physical examination was unremarkable except for purpura on his upper extremities and trunk. Blood tests showed anemia and disseminated intravascular coagulation. Chest computed tomography revealed diffuse ground-glass opacities with emphysema in his upper lungs, moderate pleural effusions, mediastinal lymphadenopathy, and enlargement of the right ventricle and main pulmonary artery. A computed tomography pulmonary angiogram showed no evidence of pulmonary embolism. Lung perfusion scintigraphy showed multiple segmental defects. Although recurrence of gastric cancer was confirmed from the results of bone marrow biopsy, bronchoscopy was not performed due to bleeding diathesis. He was treated with corticosteroids, antibiotics, and platelet transfusion, following which resolution of the abnormal lung shadows and right ventricular pressure overload along with partial alleviation of respiratory failure was observed. Because of his poor performance status, he was eventually transited to palliative care and died 6 weeks after admission. Necropsy of the lung confirmed the diagnosis of pulmonary tumor thrombotic microangiopathy with alveolar hemorrhage.

Conclusions

Pulmonary tumor thrombotic microangiopathy should be considered in the differential diagnosis of patients with cancer who present with severe pulmonary hypertension. In pulmonary tumor thrombotic microangiopathy, local inflammation in pulmonary microvasculature may contribute to pulmonary hypertension, and regulation of inflammation using corticosteroids may help improve the prognosis.

     

Indicators of acute and persistent renal damage in adult thrombotic microangiopathy

Background

Thrombotic microangiopathies (TMA) in adults such as thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are life-threatening disorders if untreated. Clinical presentation is highly variable and prognostic factors for clinical course and outcome are not well established.

Methods

We performed a retrospective observational study of 62 patients with TMA, 22 males and 40 females aged 16 to 76 years, treated with plasma exchange at one center to identify clinical risk factors for the development of renal insufficiency.

Results

On admission, 39 of 62 patients (63%) had acute renal failure (ARF) with 32 patients (52%) requiring dialysis treatment. High systolic arterial pressure (SAP, p = 0.009) or mean arterial pressure (MAP, p = 0.027) on admission was associated with acute renal failure. Patients with SAP>140 mmHg on admission had a sevenfold increased risk of severe kidney disease (OR 7.464, CI 2.097–26.565). MAP>100 mmHg indicated a fourfold increased risk for acute renal failure (OR 4.261, CI 1.400–12.972). High SAP, diastolic arterial pressure (DAP), and MAP on admission were also independent risk factors for persistent renal insufficiency with the strongest correlation for high MAP. Moreover, a high C-reactive protein (CRP) level on admission correlated with renal failure in the course of the disease (p = 0.003). At discharge, renal function in 11 of 39 patients (28%) had fully recovered, 14 patients (23%) remained on dialysis, and 14 patients (23%) had non-dialysis-dependent chronic kidney disease. Seven patients (11%) died. We identified an older age as risk factor for death.

Conclusions

High blood pressure as well as high CRP serum levels on admission are associated with renal insufficiency in TMA. High blood pressure on admission is also a strong predictor of sustained renal insufficiency. Thus, adult TMA patients with high blood pressure may require special attention to prevent persistent renal failure.     

Improvement of hypertension and vascular dysfunction by hydroxyhydroquinone-free coffee in a genetic model of hypertension

Chlorogenic acid, a polyphenol found in coffee, has antihypertensive actions, but epidemiologic data on the effects of coffee on blood pressure are controversial. Specific coffee components that inhibit the hypotensive effect of chlorogenic acid and the physiologic mechanisms underlying the effects of coffee without these components were investigated. One component, hydroxyhydroquinone (HHQ), inhibited the hypotensive effects of chlorogenic acid in spontaneously hypertensive rats (SHR). The attenuation of hypertension by HHQ-free coffee was associated with nitric oxide, the suppression of mRNA expression of NAD(P)H oxidase, and the improvement in endothelium-dependent vasodilation in the aorta. Thus, HHQ-free coffee might regulate vascular tone by improving the bioavailability of nitric oxide in SHR.     

The hypertriglyceridemic rat as a genetic model of hypertension and diabetes.

Hypertriglyceridemia was demonstrated in untreated hypertensive patients as well as in animals with genetic and experimental hypertension. The main purpose of the present study was to evaluate the possibility to use the hereditary hypertriglyceridemic (HTG) nonobese rats in hypertensive research. Direct measurement of blood pressure demonstrated significantly higher systolic, diastolic and mean arterial pressures in HTG rats in comparison with control Wistar rats. There was significant positive correlation between blood pressure and plasma triglyceride concentration (r = 0.585, n = 40, p less than 0.001). In addition, there were significantly increased plasma norepinephrine and epinephrine concentrations in HTG rats, suggesting that the stimulation of sympathetic nervous system could be one of the pathogenetic mechanisms involved in the increase of blood pressure of HTG rats.     

Reduced sympathetic neuronal uptake (uptake1) in a genetic model of desoxycorticosterone-NaCl hypertension

The effect of desoxycorticosterone (DOC)-NaCl treatment upon sympathetic neuronal uptake of norepinephrine (uptake1) was evaluated in strains of hypertension-resistant (SBN) and -prone (SBH) rats. Uninephrectomized animals were given either a placebo pellet sc and tapwater (untreated) or a 25-mg DOC pellet and 1% NaCl. Four weeks later, tail systolic pressure was significantly higher in DOC-NaCl SBH, 183 +/- 3 mm Hg, than SBN, 141 +/- 2 (P less than 0.01). [3H]Norepinephrine (NE) uptake was determined in heart slices of all four groups by incubation in Krebs buffer at 37 degrees C for 20 min at several concentrations. Preliminary studies confirmed that this is a measure of uptake1. Heart slices of DOC-NaCl-treated SBN and SBH rats had significantly reduced NE uptake at concentrations of 10-80 nM (P less than 0.01); there was no significant difference between SBN and SBH in this regard. Untreated SBH rats have been shown to have a defect in baroreflex regulation when normotensive. The results raise the possibility that the greater increase in arterial pressure caused by DOC-NaCl in SBH compared to SBN may be related to both the inborn difference in reflex function and an acquired reduction in inactivation of norepinephrine by sympathetic neuronal uptake.     

UV-resonance Raman spectroscopic study of human plasma of healthy donors and patients with thrombotic microangiopathy

Various diseases shift the composition of human plasma; hence, the relative quantification of plasma constituents offers the opportunity to use the dynamic and complex composition of plasma to gain information on novel diagnostic and prognostic factors. Since plasma contains, besides water, mostly proteins, UV-resonance Raman spectroscopy (UVRR) seems to be a suitable method for investigating plasma. With this method the signals of aromatic amino acids and proteins are selectively enhanced. In this study an UV-resonance Raman approach was used for the investigation of human plasma of healthy volunteers and patients with thrombotic microangiopathy. For comparison, selected plasma components were analyzed for a more detailed characterization of cryoprecipitates from human plasma.     

Renal denervation: a new treatment option in resistant arterial hypertension

Hypertension is one of the most prevalent cardiovascular risk factors. Despite this high prevalence and a broad availability of effective pharmaceutical agents, a significant proportion of patients do not reach treatment goals. Partly this can be explained by secondary causes of hypertension or non-compliance of patients. Nevertheless, a subgroup of patients can be diagnosed with ‘resistant hypertension’. Activation of the sympathetic nervous system is known to be an important factor in the development and progression of systemic hypertension. In this context, a percutaneous, catheter–based approach has been developed using radiofrequency energy to disrupt renal sympathetic nerves. The first studies have shown this technique to be safe, illustrated by a lack of vascular or renal injury. More importantly, catheter-based renal nerve ablation resulted in a significant reduction in blood pressure on top of traditional medical therapy. Additional to the encouraging effects shown on hypertension, a positive influence of this intervention in other conditions, characterised by sympathetic overactivation, may be expected. Though this technique seems promising, further studies are needed to address long-term safety and efficacy of renal denervation in hypertension and other disease states.     

Effects of tight blood pressure control on glomerular hypertrophy in a model of genetic hypertension and experimental diabetes mellitus

The aim of this study was to evaluate the effect of prevention of hypertension on glomerular hypertrophy, renal cell replication and accumulation of glomerular fibronectin in a model of genetic hypertension and experimental diabetes. Four-week-old streptozotocin induced spontaneously hypertensive rats (SHR) were randomized for no treatment, or for treatment with captopril, losartan or triple therapy (hydrochlorothiazide, reserpine and hydralazine) for 20 days. Increase in systolic blood pressure was equally prevented by captopril (118+/-15 mmHg), losartan (111+/-9) and triple therapy (112+/-14, p<0.0001). Glomerular size was higher (p<0.005) in diabetic SHR (27,300+/-2130 microm(2)) compared with non-diabetic SHR (23,800+/-307). The antihypertensive therapy with captopril (23,900+/-175), losartan (23,800+/-120), and triple therapy (23,400+/-210) prevented the glomerular enlargement in diabetic SHR. Glomerular expression of fibronectin was increased in diabetic SHR (7.61+/-1.22 densitometric unit) as compared to the controls (2.27+/-2.15, p<0.0001), and was decreased (p<0.0001 vs diabetic SHR) with captopril (2.49+/-1.42), losartan (1.57+/-1.1) and triple therapy (2.04+/-1.42). The number of replicating glomerular cell significantly decreased in diabetic SHR and it was restored by all three antihypertensive regimes. The glomerular expression of p27(Kip1) was increased in diabetic SHR but it was not modified by antihypertensive treatment. Strict blood pressure control, in diabetic SHR independently of the class of antihypertensive agent, restores glomerular hypertrophy and renal cellular replication, and prevents the increment in glomerular fibronectin.