Rapamycin treatment induces tubular proteinuria: role of megalin-mediated protein reabsorption

Introduction: Rapamycin is an immunosuppressor that acts by inhibiting the serine/threonine kinase mechanistic target of rapamycin complex 1. Therapeutic use of rapamycin is limited by its adverse effects. Proteinuria is an important marker of kidney damage and a risk factor for kidney diseases progression and has been reported in patients and animal models treated with rapamycin. However, the mechanism underlying proteinuria induced by rapamycin is still an open matter. In this work, we investigated the effects of rapamycin on parameters of renal function and structure and on protein handling by proximal tubule epithelial cells (PTECs). Methods: Healthy BALB/c mice were treated with 1.5 mg/kg rapamycin by oral gavage for 1, 3, or 7 days. At the end of each treatment, the animals were kept in metabolic cages and renal function and structural parameters were analyzed. LLC-PK1 cell line was used as a model of PTECs to test specific effect of rapamycin. Results: Rapamycin treatment did not change parameters of glomerular structure and function. Conversely, there was a transient increase in 24-h proteinuria, urinary protein to creatinine ratio (UPCr), and albuminuria in the groups treated with rapamycin. In accordance with these findings, rapamycin treatment decreased albumin-fluorescein isothiocyanate uptake in the renal cortex. This effect was associated with reduced brush border expression and impaired subcellular distribution of megalin in PTECs. The effect of rapamycin seems to be specific for albumin endocytosis machinery because it did not modify renal sodium handling or (Na⁺+K⁺)ATPase activity in BALB/c mice and in the LLC-PK1 cell line. A positive Pearson correlation was found between megalin expression and albumin uptake while an inverse correlation was shown between albumin uptake and UPCr or 24-h proteinuria. Despite its effect on albumin handling in PTECs, rapamycin treatment did not induce tubular injury measured by interstitial space and collagen deposition. Conclusion: These findings suggest that proteinuria induced by rapamycin could have a tubular rather than a glomerular origin. This effect involves a specific change in protein endocytosis machinery. Our results open new perspectives on understanding the undesired effect of proteinuria generated by rapamycin.

Management and outcomes of obturator hernias: a systematic review and meta-analysis

PURPOSE

Obturator Hernia (OH) is a rare type of abdominal wall hernia. It usually occurs in elderly women with late symptomatic presentation, increasing mortality rates. Surgery is the standard of care for OH, and laparotomy with simple suture closure of the defect is commonly used. Given the rarity of this disease, large studies are lacking, and data to drive management are still limited. This systematic review and meta-analysis aimed to describe current surgical options for OHs, with a focus on comparing the effectiveness and safety of mesh use with primary repair.

METHODS

PubMed, EMBASE, and Cochrane were searched for studies comparing mesh and non-mesh repair for OH. Postoperative outcomes were assessed by pooled analysis and meta-analysis. Statistical analysis was performed using RevMan 5.4.

RESULTS

One thousand seven hundred and sixty studies were screened and sixty-seven were thoroughly reviewed. We included 13 observational studies with 351 patients surgically treated for OH with mesh or non-mesh repair. One hundred and twenty (34.2%) patients underwent mesh repair and two hundred and thirty-one (65.81%) underwent non-mesh repair. A total of 145 (41.3%) underwent bowel resection, with the majority having a non-mesh repair performed. Hernia recurrence was significantly higher in patients who underwent hernia repair without mesh (RR 0.31; 95% CI 0.11-0.94; p = 0.04). There were no differences in mortality (RR 0.64; 95% CI 0.25-1.62; p = 0.34; I² = 0%) or complication rates (RR 0.59; 95% CI 0.28-1.25; p = 0.17; I² = 50%) between both groups.

CONCLUSION

Mesh repair in OH was associated with lower recurrence rates without an increase in postoperative complications. While mesh in clean cases is more likely to offer benefits, an overall recommendation regarding its use in OH repair cannot be made due to potential bias across studies. Given that many OH patients are frail and present emergently, the decision to use mesh is complex and should consider the patient's clinical status, comorbidities, and degree of intraoperative contamination.

The single-syringe versus the double-syringe techniques of adenosine administration for supraventricular tachycardia: a systematic review and meta-analysis

Funding Acknowledgements

Type of funding sources: None.

Introduction

Intravenous double-syringe technique (DST) of adenosine administration consists of an intravenous bolus of adenosine via three-way stopcock followed by an immediate 10-20ml sodium chloride 0.9% flush and is the recommended first-line treatment for stable supraventricular tachycardia (SVT). However, an alternative single-syringe technique (SST) method for adenosine administration has been described. This consists of diluting adenosine with sodium chloride 0.9% to a total volume of 15-20ml and was recently found to be potentially beneficial in several studies.

Purpose

We aimed to perform a meta-analysis of the SST versus the DST of adenosine administration as treatments for SVT.

Methods

We systematically searched EMBASE, PubMed, Cochrane, and ClinicalTrials.gov databases for randomised controlled trials (RCTs) and non-randomised studies of intervention (NRSIs) comparing the DST to SST adenosine administration in patients with SVT. The risk of bias was assessed by RoB-2 for RCTs and ROBINS-I for NRSIs. Outcomes included termination rate, termination rate at first dose, total administered dose, adverse effects, and discharge rate.

Results

We included four studies (three RCTs and one NRSI) with a total of 180 (60.55% female) patients, of whom 100 (55.55%) underwent the SST of adenosine administration. The three RCTs were considered of some concerns due to no pre-specified analysis in all studies and deviation from the intended intervention in one study. The NRSI was considered to carry a serious risk of bias by no analysis method that controlled for confounding, the possible influence of the outcome measure by knowledge of the intervention received, and no pre-specified analysis. No significant difference was found between treatment groups regarding termination rate (p = 0.22, Fig 1a), termination rate restricted to RCTs (p = 0.49, Fig 1b), total administered dose (p = 0.29, Fig 2a) and discharge rate (p = 0.1, Fig 2b). Termination rate at first dose (OR 2.87; CI 1.11-7.41; p = 0.03; I² = 0%, Fig 1c) was significantly increased in patients who received the SST. Major adverse effects were observed in only one study, with one patient suffering extravasation and phlebitis in the DST group.

Conclusion

To our knowledge, this is the first meta-analysis studying SST versus conventional DST for the management of SVT. This study suggests that the SST may be as safe as DST, equally effective for SVT termination, or even potentially more effective with the first dose. The SST would represent a simpler and more rapid approach, obviating the need for syringe switching or three-way stopcock, and reducing the margin of error in adenosine administration. To our knowledge, this is the highest quality evidence to date. Our results demonstrate that the current evidence is sufficient to support both SST and DST. However, favouring one technique over the other is not feasible given the limited sample size.

Subclinical Acute Kidney Injury in COVID-19: Possible Mechanisms and Future Perspectives

Since the outbreak of COVID-19 disease, a bidirectional interaction between kidney disease and the progression of COVID-19 has been demonstrated. Kidney disease is an independent risk factor for mortality of patients with COVID-19 as well as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leading to the development of acute kidney injury (AKI) and chronic kidney disease (CKD) in patients with COVID-19. However, the detection of kidney damage in patients with COVID-19 may not occur until an advanced stage based on the current clinical blood and urinary examinations. Some studies have pointed out the development of subclinical acute kidney injury (subAKI) syndrome with COVID-19. This syndrome is characterized by significant tubule interstitial injury without changes in the estimated glomerular filtration rate. Despite the complexity of the mechanism(s) underlying the development of subAKI, the involvement of changes in the protein endocytosis machinery in proximal tubule (PT) epithelial cells (PTECs) has been proposed. This paper focuses on the data relating to subAKI and COVID-19 and the role of PTECs and their protein endocytosis machinery in its pathogenesis.

SARS-CoV-2 spike protein inhibits megalin-mediated albumin endocytosis in proximal tubule epithelial cells

Patients with COVID-19 have high prevalence of albuminuria which is used as a marker of progression of renal disease and is associated with severe COVID-19. We hypothesized that SARS-CoV-2 spike protein (S protein) could modulate albumin handling in proximal tubule epithelial cells (PTECs) and, consequently contribute to the albuminuria observed in patients with COVID-19. In this context, the possible effect of S protein on albumin endocytosis in PTECs was investigated. Two PTEC lines were used: HEK-293A and LLC-PK1. Incubation of both cell types with S protein for 16 h inhibited albumin uptake at the same magnitude. This effect was associated with canonical megalin-mediated albumin endocytosis because: (1) DQ-albumin uptake, a marker of the lysosomal degradation pathway, was reduced at a similar level compared with fluorescein isothiocyanate (FITC)-albumin uptake; (2) dextran-FITC uptake, a marker of fluid-phase endocytosis, was not changed; (3) cell viability and proliferation were not changed. The inhibitory effect of S protein on albumin uptake was only observed when it was added at the luminal membrane, and it did not involve the ACE2/Ang II/AT1R axis. Although both cells uptake S protein, it does not seem to be required for modulation of albumin endocytosis. The mechanism underlying the inhibition of albumin uptake by S protein encompasses a decrease in megalin expression without changes in megalin trafficking and stability. These results reveal a possible mechanism to explain the albuminuria observed in patients with COVID-19.

Hyperphosphatemia is associated with cardiac valve calcification in chronic hypoparathyroidism

PURPOSE

To evaluate the association between metabolic abnormalities and cardiovascular risk factors in patients with chronic hypoparathyroidism (HPP).

PATIENTS AND METHODS

Patients 18 years and older, glomerular filtration > 30 mL/min/1.73 m² and no documented coronary artery disease were selected. Serum calcium, phosphorus, glucose, lipids, PTH, 25(OH)D and FGF23 were measured. Cardiovascular risk was estimated by the European Society of Cardiology (ESC) calculator. Transthoracic echocardiogram and carotid ultrasound were performed to detect carotid plaques (CP), carotid intima-media thickness (IMT), cardiac valve calcification (CVC), and left ventricular hypertrophy (LVH).

RESULTS

Thirty-seven patients (94.6% female), aged 56.0 ± 13.5 years and HPP duration 7.0 (4.0; 11.3) years, were included. Fifteen were classified as low cardiovascular risk, 9 as intermediate risk, 9 as high risk and none as very high risk. The prevalence of CP, CVC and LVH was 24.3%, 24.3% and 13.5%, respectively. IMT values were within normal ranges in all cohort. FGF23 were not associated with CP, IMT, CVC or LVH. After logistic regression, phosphorus was the only significant metabolic variable impacting CVC in univariate analysis (OR 2.795; 95% CI 1.132-6.905; p = 0.026), as well as in the multivariate analysis (OR 3.572; 95% CI 1.094-11.665; p = 0.035). Analysis by ROC curve showed serum phosphorus > 5.05 mg/dL (AUC 0.748; CI 0.584-0.877; p = 0.05) as the best cutoff point associated with valve heart calcification (sensitivity 78%; negative predictive value 91.3%).

CONCLUSION

Hyperphosphatemia was associated with CVC in HPP patients. Further studies are needed to investigate whether the control of hyperphosphatemia may reduce cardiovascular risk in this population.

Crosstalk between the signaling pathways triggered by angiotensin II and adenosine in the renal proximal tubules: implications for modulation of Na(+)-ATPase activity

We have previously demonstrated that adenosine (Ado) reverses the stimulatory effect of angiotensin II (Ang II) on Na(+)-ATPase activity via the A(2A) receptor. In this work, the molecular mechanism involved in Ado-induced shutdown in the signaling pathway triggered by 10(-8)M Ang II was investigated. It was observed that: (1) both 10(-12)M PMA (a PKC activator) and 5x10(-8)M U73122 (an inhibitor of PI-PLCbeta) prevent the reversion effect induced by 10(-6)M Ado (only observed in the presence of 10(-6)M DPCPX (an A(1) receptor antagonist)) on Ang II-stimulated Na(+)-ATPase and PKC activities; (2) Ang II-stimulated PKC activity was reversed by 10(-6)M forskolin (an adenylyl cyclase activator) or 10(-8)M PKA inhibitory peptide and 10(-8)M DMPX (an A(2) receptor-selective antagonist). Considering that PMA prevents the inhibitory effect of Ado on Ang II-stimulated Na(+)-ATPase and PKC activities, it is likely that the PMA-induced effect, i.e. PKC activation, is downstream of the target for Ado-induced reversion of Ang II stimulation of Na(+)-ATPase activity. We investigated the hypothesis that PI-PLCbeta could be the target for Ado-induced PKA activation. Our data demonstrate that Ang II-stimulated PI-PLCbeta activity was reversed by Ado or 10(-7)M cAMP; the reversibility of the Ado-induced effect was prevented by either DMPX or PKA inhibitory peptide. These data demonstrate that Ado-induced PKA activation reduces Ang II-induced stimulation of PI-PLCbeta.

PTEN and p53 expression in primary ovarian carcinomas: immunohistochemical study and discussion of pathogenetic mechanisms

Proapoptotic molecules have been studied in epithelial ovarian neoplasms as possible indicators of the pathogenetic pathways, as targets for new therapeutic approaches, and as prognostic markers. PTEN and p53 are proteins that have many different regulatory functions, including apoptosis. We have studied their immunohistochemical expression in 70 cases of primary ovarian carcinomas (26 serous, 27 endometrioid, and 17 mucinous) and compared the results with morphologic parameters (histologic grade, subtype) and clinical data (age, stage, tumor size). Statistical analyses showed a significantly higher expression of p53 in histologically high-grade tumors (grades 2 and 3), mainly of the serous subtype. A statistical tendency of higher expression of p53 in older patients (P= 0.08) was also observed. The loss of expression of PTEN was significantly more frequent in grade 1 endometrioid adenocarcinomas. These markers did not show association with volume or stage of the tumor. p53 is associated with serous carcinoma, loss of differentiation, and older patients, whereas PTEN inactivation is an early event in carcinogenesis of the endometrioid subtype, as observed in type I endometrial carcinoma. Our results are in keeping with different pathogenetic pathways in subtypes of ovarian carcinoma, prompting the search for new strategies of prevention and treatment.

Is it possible to use modification of diet in renal disease (MDRD) equation in a Brazilian population?

BACKGROUND

Accurate assessment of kidney function level is the key to the identification and management of chronic kidney disease (CKD). Glomerular filtration rate (GFR) is the best measure of overall kidney function in health and disease. There is no consensus about the method to be used routinely to measure and/or estimate GFR. The objectives of this study were to assess which method correlates better with creatinine (Cr) clearance, extensively used in medical practice, as well as assessing the efficacy of the modification of diet in renal disease (MDRD) equation, in our population.

METHODS

We studied 262 adult out-patients with stable CKD on conservative treatment. GFR was evaluated by Cr clearance, Cockcroft-Gault (CG) formula, the mean of urea and Cr clearances (total clearance (TCl)), the MDRD study equation, with and without the variable for African-Americans (MDRD1) and the simplified one (MDRDs). Data were analyzed by Pearson's correlation coefficient (r) and Bland & Altman plot analysis.

RESULTS

Pearson's correlation showed that all methods where similar when compared to Cr clearance. A high correlation was observed between CG and MDRD equations, and TCl and MDRD equations showed the worst correlation. Among the MDRD equations, no differences were found. Bland-Altman plot analysis indicated a concordance among the studied methods.

CONCLUSION

The CG formula could replace Cr clearance in our population, being simpler than and equally as sensitive as the MDRD equation.

Adenosine reverses the stimulatory effect of angiotensin II on the renal Na+-ATPase activity through the A2 receptor

In the present paper, we report the modulation of the Angiotensin II (Ang II)-stimulated Na+-ATPase activity of the proximal tubule basolateral membrane by adenosine (Ado). Preincubation of isolated basolateral membrane with 10(-8)M Ang II increases the Na+-ATPase activity from 7.5+/-0.3 (control) to 14.6+/-0.9 nmol Pi x mg(-1)x min(-1)nmol Pi x mg(-1) x min(-1) (p<0.05). Incubation of Ang II-stimulated enzyme with 10(-6)M Ado, in the presence of the A1 receptor antagonist DPCPX (10(-6)M), completely reverses the Ang II-induced effect bringing the Na+-ATPase activity to the basal level. The following evidences demonstrate involvement of the A2 receptor/Gs protein/adenylyl cyclase/PKA signaling pathway in the inhibitory effect induced by Ado on the Ang II-stimulated Na+-ATPase activity in the presence of the DPCPX: 1) the inhibitory effect of Ado is abolished by the A2 receptor selective antagonist DMPX (10(-8)M); 2) the effect induced by Ado is blocked by 10(-8)M GDPbetaS and mimicked by 10(-9)M cholera toxin and 10(-8)M GTPgammaS; 3) the stimulatory effect of Ang II is reduced by 10(-6)M forskolin, an activator of adenylyl cyclase, or 10(-6)M cAMP; 4) Ado stimulates PKA activity; 5) the inhibitory effect induced by this nucleoside is reversed by the PKA inhibitor peptide.

Expression of p53, c-erbB-2, Ki-67, and CD34 in granulosa cell tumor of the ovary

The purpose of this study is to investigate the expression of p53, c-erbB-2, Ki-67, and angiogenic activity and their correlation with the clinicopathologic characteristics in a series of granulosa cell tumors of the ovary (GCTO). Eighteen GCTO cases assisted at the Department of Obstetrics and Gynecology, School of Medical Science, UNICAMP, after diagnostic confirmation by three pathologists, were submitted to immunohistochemistry for assessment of p53, c-erbB-2, Ki-67, and CD34 expressions. The mean tumor size was 13 cm (range: 4-30 cm). Six (33%) cases presented with extraovarian disease. Thirteen (72%) cases presented some solid diffuse or sarcomatoid pattern and six (33%) moderate or strong atypia. Fourteen cases presented </=2 mitoses/10 HPF. Thirteen cases were focally positive for Ki-67. The mean Ki-67 proliferative index was 1.0%. One case presented positive expression for mutant p53 but all cases were negative for c-erbB-2 expression. The mean microvascular density was 28.9/mm2 (range: 0-50). No significant correlations could be established between the biologic markers and clinicopathologic variables. GCTO showed a markedly low rate of immunohistochemical staining for p53 or c-erbB-2 overexpression/amplification, as well as low proliferative and angiogenic activities. Further studies are urgently needed to elaborate the factors responsible for the highly unpredictable clinical course of GCTO.