Potential Mechanisms Involved in Chronic Kidney Disease of Unclear Etiology

BACKGROUND AND OBJECTIVES

The etiology of chronic kidney disease of unclear etiology, also known as Mesoamerican nephropathy, remains unclear. We investigated potential etiologies for Mesoamerican nephropathy in an immigrant dialysis population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Migrants with Mesoamerican nephropathy kidney failure (n=52) were identified by exclusion of known causes of kidney disease and compared using a cross-sectional survey with demographically similar patients with kidney failure from other causes (n=63) and age/sex/place of origin-matched healthy participants (n=16). Survey results were extended to the bench; C57BL/6 mice (n=73) received 10-15 weekly intraperitoneal injections of paraquat (a reactive oxygen species-generating herbicide) or vehicle. Kidney function, histology, and expression of organic cation transporter-2 (proximal tubule entry for paraquat) and multidrug and toxin extrusion 1 (extrusion pathway) were examined. Kidney biopsies from Nicaraguan patients with acute Mesoamerican nephropathy were stained for the above transporters and compared with patients with tubulointerstitial nephritis and without Mesoamerican nephropathy.

RESULTS

Patients with Mesoamerican nephropathy and kidney failure were young agricultural workers, almost exclusively men; the majority were from Mexico and El Salvador; and they had prior exposures to agrochemicals, including paraquat (27%). After adjustment for age/sex, exposure to any agrochemical or paraquat was associated with Mesoamerican nephropathy kidney failure (odds ratio, 4.86; 95% confidence interval, 1.82 to 12.96; P=0.002 and odds ratio, 12.25; 95% confidence interval, 1.51 to 99.36; P=0.02, respectively). Adjusted for age/sex and other covariates, 1 year of agrochemical exposure was associated with Mesoamerican nephropathy kidney failure (odds ratio, 1.23; 95% confidence interval, 1.04 to 1.44; P=0.02). Compared with 16 matched healthy controls, Mesoamerican nephropathy kidney failure was significantly associated with exposure to paraquat and agrochemicals. Paraquat-treated male mice developed kidney failure and tubulointerstitial nephritis consistent with Mesoamerican nephropathy. Organic cation transporter-2 expression was higher in male kidneys versus female kidneys. Paraquat treatment increased organic cation transporter-2 expression and decreased multidrug and toxin extrusion 1 expression in male kidneys; similar results were observed in the kidneys of Nicaraguan patients with Mesoamerican nephropathy.

CONCLUSIONS

Exposure to agrochemicals is associated with Mesoamerican nephropathy, and chronic exposure of mice to paraquat, a prototypical oxidant, induced kidney failure similar to Mesoamerican nephropathy.

Spectrum of Biopsy-proven Native Kidney Disease in Central India

Spectrum of native renal biopsy reports varies geographically. Here, we tried to determine the prevalence of renal biopsy disorders and compare it with other studies. Retrospective study was performed at Saraswati Kidney Care Center, Nagpur and Jawaharlal Nehru Medical College, Sawangi, India. All the native kidney biopsies from January 2017 to March 2020 were included in the analysis. Demographic details of all the patients were recorded. Renal diseases were classified as glomerular, tubulo-interstitial, predominant vascular involvement and other disease categories. Total 347 native kidney biopsies were performed during the study period. Mean age of the patients at the time of biopsy was 41.41 ± 15.75 years. Majority of patients were males (58.5%). Most common indication for kidney biopsy was nephrotic syndrome (36.3%) followed by nephritic syndrome (19.9%). Among the glomerular diseases (GDs), 69% were primary glomerulopathies and 31% were secondary GDs. Immunoglobulin (IgA) nephropathy (30.85%) was the most common primary GD followed by membranous nephropathy (MN) (26.59%), focal segmental glomerulosclerosis (FSGS) (17.02 %) and minimal change disease (14.36 %). Among secondary glomerulopathies, lupus nephritis was the most common histopathological diagnosis (31.8%) followed by diabetic nephropathy (26.1%), amyloidosis (17%), infection related glomerulonephritis (11.3%), light chain deposition disease (4%) and anti-neutrophil cytoplasmic antibody associated vasculitis (3.4%). In tubulointerstitial disease, 33.3% had acute tubulointerstitial nephritis, whereas each 26.6% had acute tubular injury and cast nephropathy. The most prevalent diagnosis in our only study from central India was IgA nephropathy followed by MN and FSGS. Data analysis at regular intervals helps in understanding the changing trend of prevalence of native kidney disease and also gives understanding of geographical variations.

Clinical and histopathological analyses of kidney biopsies in a single center for 7 years

Kidney biopsy is the most important tool for diagnosing kidney disease and can be helpful in determining treatment and prognosis. Pathological spectra vary by country, region, race, sex, and age. We are the first to investigate the pathological spectrum of biopsy-proven kidney disease in Gyeongnam province of South Korea. We retrospectively analyzed 631 patients who underwent a kidney biopsy between 2013 and 2019 at Gyeongsang National University Hospital. The mean age of the 631 patients was 51.5 ± 18.1 years, and 361 patients (57.2%) were male. The mean estimated glomerular filtration rate by serum creatinine (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) was 68.0 ± 45.7 mL/min/1.73 m2. The mean systolic blood pressure was higher in 2017, 2018, and 2019 than in 2013 (P = .002). Hypertension (47.4%) was the most common comorbid disease, followed by diabetes (18.2%) and dyslipidemia (10.9%). Common clinical syndromes at the time of biopsy were renal insufficiency (42.0%) and nephrotic syndrome (33.9%). The prevalence of primary and secondary glomerular disease and tubulointerstitial disease were 71.4%, 16.9%, and 5.4%, respectively. Immunoglobulin A nephropathy was the most common primary glomerular disease (34.9%). Diabetic nephropathy was the most common secondary glomerular disease, followed by lupus nephritis. Tubulointerstitial disease was underestimated, as in other reports. Our data can be a useful reference for diagnosing kidney disease and understanding the patients in our province.

Renal sarcoidosis

Renal sarcoidosis (RS) is a rare form of sarcoidosis that results in granulomatous inflammation of renal parenchyma. We describe the epidemiology, pathogenesis, clinical features, diagnostic approach, treatment strategies and outcomes of this condition. RS occurs most commonly at the time of initial presentation of sarcoidosis but can at any time along the course of the disease. The most common presenting clinical manifestations of RS are renal insufficiency or signs of general systemic inflammation. End-stage renal disease requiring dialysis is a rare initial presentation of RS. The diagnosis of RS should be considered in patients who present with renal failure and have either a known diagnosis of sarcoidosis or have extra-renal features consistent with sarcoidosis. A renal biopsy helps to establish the diagnosis of RS, with interstitial non-caseating granulomas confined primarily to the renal cortex being the hallmark pathological finding. However, these histologic findings are not specific for sarcoidosis, and alternative causes for granulomatous inflammation of the renal parenchyma should be excluded. Corticosteroids are the drug of choice for RS. Although RS usually responds well to corticosteroids, the disease may have a chronic course and require long-term immunosuppressive therapy. The risk of progression to ESRD is rare.

Evaluating tubulointerstitial compartments in renal biopsy specimens using a deep learning-based approach for classifying normal and abnormal tubules

Renal pathology is essential for diagnosing and assessing the severity and prognosis of kidney diseases. Deep learning-based approaches have developed rapidly and have been applied in renal pathology. However, methods for the automated classification of normal and abnormal renal tubules remain scarce. Using a deep learning-based method, we aimed to classify normal and abnormal renal tubules, thereby assisting renal pathologists in the evaluation of renal biopsy specimens. Consequently, we developed a U-Net-based segmentation model using randomly selected regions obtained from 21 renal biopsy specimens. Further, we verified its performance in multiclass segmentation by calculating the Dice coefficients (DCs). We used 15 cases of tubulointerstitial nephritis to assess its applicability in aiding routine diagnoses conducted by renal pathologists and calculated the agreement ratio between diagnoses conducted by two renal pathologists and the time taken for evaluation. We also determined whether such diagnoses were improved when the output of segmentation was considered. The glomeruli and interstitium had the highest DCs, whereas the normal and abnormal renal tubules had intermediate DCs. Following the detailed evaluation of the tubulointerstitial compartments, the proximal, distal, atrophied, and degenerated tubules had intermediate DCs, whereas the arteries and inflamed tubules had low DCs. The annotation and output areas involving normal and abnormal tubules were strongly correlated in each class. The pathological concordance for the glomerular count, t, ct, and ci scores of the Banff classification of renal allograft pathology remained high with or without the segmented images. However, in terms of time consumption, the quantitative assessment of tubulitis, tubular atrophy, degenerated tubules, and the interstitium was improved significantly when renal pathologists considered the segmentation output. Deep learning algorithms can assist renal pathologists in the classification of normal and abnormal tubules in renal biopsy specimens, thereby facilitating the enhancement of renal pathology and ensuring appropriate clinical decisions.

Assessment of renal microcirculation in biopsy-proven tubulointerstitial nephritis in patients with and without glomerular disease: the role of resistive index

BACKGROUND

Renal resistive index (RRI) measured by Doppler sonography is a marker of microvascular status and it is associated with changes in renal function. Aim of the study was to assess RRI in biopsy-proven tubulointerstitial nephritis (TIN) in patients with and without glomerular disease.

METHODS

132 consecutive patients underwent to native renal biopsy with diagnosis of isolated TIN or in association with glomerulonephritis. Estimated glomerular filtration rate (eGFR), 24-hour urinary protein excretion and renal ecocolorDoppler ultrasonography with RRI assessment were performed at time of enrollment.

RESULTS

Patients with isolated-TIN had significantly higher RRI than both patients with non-immunoglobulin A glomerulonephritis (non-IgA-TIN) [0.73 (0.68-0.77) vs 0.64 (0.60-0.67), p < 0.001] and patients with IgA nephropathy (IgAN) [0.73 (0.68-0.77) vs 0.66 (0.60-0.71), p < 0.01]. Patients with isolated-TIN had mainly RRI ≥ 0.70 (n = 15, 65.2%) with the respect to patients with non-IgA-TIN (n = 7, 12.3%) and patients with IgAN (n = 17, 32.7%). A negative linear correlation was found between RRI and hemoglobin (r = 0.233, p < 0.01) and between RRI and eGFR (r = 0.537, p < 0.001).

CONCLUSION

Tubulointerstitial damage is the most accurate histological lesion that correlates with eGFR and renal impairment. RRI can be a useful parameter to detect tubulointerstitial lesions.

TRPC6 Inactivation Reduces Albuminuria Induced by Protein Overload in Sprague Dawley Rats

Canonical transient receptor potential-6 (TRPC6) channels have been implicated in familial and acquired forms of focal and segmental glomerulosclerosis (FSGS), and in renal fibrosis following ureteral obstruction in mice. TRPC6 channels also appear to play a role in driving glomerular disease in aging and in autoimmune glomerulonephritis. In the present study, we examine the role of TRPC6 in the proteinuric state caused by prolonged albumin overload (AO) in Sprague Dawley rats induced by daily injections of exogenous albumin. This was assessed in rats with a global and constitutive inactivation of TRPC6 channels (Trpc6del/del rats) and in wild-type littermates (Trpc6wt/wt rats). AO for 14 and 28 days caused increased urine albumin excretion that was significantly attenuated in Trpc6del/del rats compared to Trpc6wt/wt controls. AO overload did not induce significant glomerulosclerosis or azotemia in either genotype. AO induced mild tubulointerstitial disease characterized by fibrosis, hypercellularity and increased expression of markers of fibrosis and inflammation. Those changes were equally severe in Trpc6wt/wt and Trpc6del/del rats. Immunoblot analysis of renal cortex indicated that AO increased the abundances of TRPC3 and TRPC6, and caused a nearly complete loss of TRPC5 in Trpc6wt/wt rats. The increase in TRPC3 and the loss of TRPC5 occurred to the same extent in Trpc6del/del rats. These data also suggest that TRPC6 plays a role in the normal function of the glomerular filtration barrier. However, whether TRPC6 inactivation protects the tubulointerstitial compartments in Sprague Dawley rats depends on the disease model examined.

Tubulointerstitial nephritis: a biopsy case series of 139 Japanese patients

BACKGROUND

Tubulointerstitial nephritis (TIN) is an important cause of acute kidney injury (AKI) and advanced CKD. Only a limited number of studies have reported etiology-based differences in the clinical and/or histopathological properties and kidney outcomes of the biopsy-proven TIN.

METHODS

Patients with biopsy-proven TIN identified from 2005 to 2016 in five hospitals were categorized based on the etiologies and were retrospectively analyzed in relation to the clinicopathological findings and kidney outcomes.

RESULTS

Among 4815 biopsy cases screened, 153 Japanese TIN patients were identified, of whom 139 patients with ≥ 6 months of follow-up data (median 58 years old, 45.3% female, median 31.5 months follow-up) were further analyzed. TIN was drug-induced in 32.4%, autoimmune-related in 24.5%, of unknown etiology in 27.3% and other disease-related in 15.8%. Non-steroidal anti-inflammatory drugs and antibiotics were major causative drugs in drug-induced TIN, and IgG4-related disease, Sjögren's syndrome and sarcoidosis were common in autoimmune-related TIN. Among etiology groups, drug-induced TIN showed advanced AKI with elevated serum creatinine (sCr) and increased C-reactive protein levels at the diagnosis. TIN patients with autoimmune diseases showed less-severe AKI, but were more frequently treated with corticosteroids than others. Tubulointerstitial injury expansion in biopsy specimens was comparable among the groups. Complete or partial kidney function recovery at 6 months was more frequent in drug-induced and autoimmune-related TIN than in others. sCr levels at 6 months were similar among the groups.

CONCLUSIONS

This largest case series study of the biopsy-proven TIN in Japan provides detailed information regarding both etiology-based clinicopathological properties and kidney outcomes.

Acute Tubulointerstitial Nephritis in Rosai-Dorfman Disease Mimicking IgG4-related Disease

Rosai-Dorfman-Destombes disease (RDD) is a non-Langerhans cell histiocytosis characterized by the accumulation of histiocytes inside the lymph nodes or extranodally. The association between RDD and IgG4-related disease (IgG4-RD) is discussed. We herein report a case of RDD manifesting as acute tubulointerstitial nephritis mimicking IgG4-RD. The first renal biopsy showed severe tubulointerstitial nephritis with infiltration of S100-positive histiocytes and IgG4-positive plasma cells; storiform fibrosis and obliterative phlebitis were not confirmed. After prednisolone therapy, IgG4-positive cells and S100-positive histiocytes were decreased, but the IgG4/IgG ratio increased despite clinical improvement. These findings indicated extranodal RDD in the kidney presenting as tubulointerstitial nephritis.

Acute kidney injury in patients with COVID-19: Epidemiology, pathogenesis and treatment

Acute kidney injury occurs in about 30% of patients hospitalized with coronavirus disease 2019 (COVID-19) and is one of the most common extrapulmonary complications of this disease. The highest risk of acute kidney injury is found in hospitalized patients who require mechanical ventilation. The pathogenesis of acute kidney injury in COVID-19 is multifactorial and seems to not be fully understood. Both direct and indirect mechanisms of kidney injury caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) should be considered. The histological picture of kidney specimens obtained from patients with acute kidney injury in the course of COVID-19 is dominated by acute tubular necrosis. Some patients also have acute interstitial nephritis, blood clots in the kidney vessels and focal segmental glomerulosclerosis (the variant with collapsing vascular loops). Acute kidney injury in COVID-19 is primarily caused not by direct viral effect, but by indirect pathophysiological mechanisms. The histopathological findings in these patients does not differ from the majority of the other patients with acute kidney injury. The main pathophysiological mechanisms underlying acute kidney injury in COVID-19 are: hemodynamic abnormalities, hypoxia and cytokine storm. The methods of treating the underlying disease, i.e., COVID-19 in patients with acute kidney injury and those without acute kidney injury are similar. However, it should be stressed that in the treatment of COVID-19 accompanied by acute kidney injury, the contraindication to remdesivir is estimated using glomerular filtration rate (eGFR) <30 mL/min/1.73 m2. The general principles of management in patients with both, COVID-19 and acute kidney injury do not differ from the principles of management in patients with acute kidney injury due to the other causes.

All-trans retinoic acid regulating angiopoietins-1 and alleviating extracellular matrix accumulation in interstitial fibrosis rats

All-trans retinoic acid (ATRA) is one of essentially active metabolite of vitamin A, and plays an important role in diverse physiological processes, such as cellular growth and function. Renal interstitial fibrosis (RIF) is a common pathological characteristic of chronic renal disease causing end-stage renal disease currently lacking effective treatment. Low level of Angiopoietins-1 (Angpt-1) is associated with extracellular matrix accumulation and fibrosis diseases. This study was performed to assess the association of ATRA with Angpt-1 in RIF disease. Rats were divided into three groups: group of sham (SHO group), group of unilateral ureteral obstruction group (UUO group), UUO mice administrated daily at the dose of ATRA (ATRA group). Masson-staining was used to detect the histologic lesion. Immunohistochemistry and Western-blot were applied to determine the targeted proteins. RIF score was significantly increased in UUO rats when compared with that of SHO group, and the fibrosis score was notably reduced in ATRA group. Transforming growth factor-β1 (TGF-β1), collagen IV (Col-IV) and fibronectin (FN) expressions in UUO group were significantly up-regulated, whereas Angpt-1 expression was significantly down-regulated compared with the SHO group. ATRA treatment reduced TGF-β1, Col-IV and FN expressions and improved Angpt-1 expression compared with the UUO group. The protein expression of Angpt-1 in kidney tissue of UUO group was negatively correlated with RIF index and protein expressions of Col-IV, FN and TGF-β1. In conclusion, low expression of Angpt-1 was associated with the RIF disease and ATRA treatment can increase the Angpt-1 and alleviate the RIF lesion in UUO rats.

Aristolochic Acid Induces Renal Fibrosis and Senescence in Mice

The kidney is one of the most susceptible organs to age-related impairments. Generally, renal aging is accompanied by renal fibrosis, which is the final common pathway of chronic kidney diseases. Aristolochic acid (AA), a nephrotoxic agent, causes AA nephropathy (AAN), which is characterized by progressive renal fibrosis and functional decline. Although renal fibrosis is associated with renal aging, whether AA induces renal aging remains unclear. The aim of the present study is to investigate the potential use of AAN as a model of renal aging. Here, we examined senescence-related factors in AAN models by chronically administering AA to C57BL/6 mice. Compared with controls, the AA group demonstrated aging kidney phenotypes, such as renal atrophy, renal functional decline, and tubulointerstitial fibrosis. Additionally, AA promoted cellular senescence specifically in the kidneys, and increased renal p16 mRNA expression and senescence-associated β-galactosidase activity. Furthermore, AA-treated mice exhibited proximal tubular mitochondrial abnormalities, as well as reactive oxygen species accumulation. Klotho, an antiaging gene, was also significantly decreased in the kidneys of AA-treated mice. Collectively, the results of the present study indicate that AA alters senescence-related factors, and that renal fibrosis is closely related to renal aging.

NSC828779 Alleviates Renal Tubulointerstitial Lesions Involving Interleukin-36 Signaling in Mice

Renal tubulointerstitial lesions (TILs), a common pathologic hallmark of chronic kidney disease that evolves to end-stage renal disease, is characterized by progressive inflammation and pronounced fibrosis of the kidney. However, current therapeutic approaches to treat these lesions remain largely ineffectual. Previously, we demonstrated that elevated IL-36α levels in human renal tissue and urine are implicated in impaired renal function, and IL-36 signaling enhances activation of NLRP3 inflammasome in a mouse model of TILs. Recently, we synthesized NSC828779, a salicylanilide derivative (protected by U.S. patents with US 8975255 B2 and US 9162993 B2), which inhibits activation of NF-κB signaling with high immunomodulatory potency and low IC50, and we hypothesized that it would be a potential drug candidate for renal TILs. The current study validated the therapeutic effects of NSC828779 on TILs using a mouse model of unilateral ureteral obstruction (UUO) and relevant cell models, including renal tubular epithelial cells under mechanically induced constant pressure. Treatment with NSC828779 improved renal lesions, as demonstrated by dramatically reduced severity of renal inflammation and fibrosis and decreased urinary cytokine levels in UUO mice. This small molecule specifically inhibits the IL-36α/NLRP3 inflammasome pathway. Based on these results, the beneficial outcome represents synergistic suppression of both the IL-36α-activated MAPK/NLRP3 inflammasome and STAT3- and Smad2/3-dependent fibrogenic signaling. NSC828779 appears justified as a new drug candidate to treat renal progressive inflammation and fibrosis.

Mesoamerican nephropathy: A not so unknown chronic kidney disease

From 2000, Mesoamerican region has reached an important rate of chronic kidney disease of unknown etiology. Under the name of Meroamerican Nephropathy (MeN) several hypotheses (including dehydration, heat stress, environmental or toxic exposure or even infections) have tried to explain the etiology this new disease. MeN affects young men, agricultural workers exposed to high temperatures. MeN courses with unspecific symptoms as low-grade fever and dysuria and progressive kidney disease with impaired renal function and hydroelectrolyte disturbances. The diagnosis requires kidney biopsy showing tubule-interstitial nephritis (usually at chronic stage). Although MeN conditions a high morbi-mortality in endemic regions, there is a lack of specific treatment and only preventive measures have demonstrated some effect of prognosis (avoid heat stress, constant hydration). In this review we aim to summarize the available information of MeN, illustrating the information in a case report.

Gene Expression Profiling in Kidney Transplants with Immune Checkpoint Inhibitor-Associated Adverse Events

BACKGROUND AND OBJECTIVES

Immune checkpoint inhibitors are increasingly used to treat various malignancies, but their application in patients with kidney transplants is complicated by high allograft rejection rates. Immune checkpoint inhibitor-associated rejection is a novel, poorly understood entity demonstrating overlapping histopathologic features with immune checkpoint inhibitor-associated acute interstitial nephritis, which poses a challenge for diagnosis and clinical management. We sought to improve the understanding of these entities through biopsy-based gene expression analysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

NanoString was used to measure and compare the expression of 725 immune-related genes in 75 archival kidney biopsies, including a 25-sample discovery cohort comprising pure T cell-mediated rejection and immune checkpoint inhibitor-associated acute interstitial nephritis and an independent 50-sample validation cohort comprising immune checkpoint inhibitor-associated acute interstitial nephritis, immune checkpoint inhibitor-associated T cell-mediated rejection, immune checkpoint inhibitor-associated crescentic GN, drug-induced acute interstitial nephritis, BK virus nephropathy, and normal biopsies.

RESULTS

Significant molecular overlap was observed between immune checkpoint inhibitor-associated acute interstitial nephritis and T cell-mediated rejection. Nevertheless, IFI27, an IFN-α-induced transcript, was identified and validated as a novel biomarker for differentiating immune checkpoint inhibitor-associated T cell-mediated rejection from immune checkpoint inhibitor-associated acute interstitial nephritis (validation cohort: P<0.001, area under the receiver operating characteristic curve =100%, accuracy =86%). Principal component analysis revealed heterogeneity in inflammatory gene expression patterns within sample groups; however, immune checkpoint inhibitor-associated T cell-mediated rejection and immune checkpoint inhibitor-associated acute interstitial nephritis both demonstrated relatively more molecular overlap with drug-induced acute interstitial nephritis than T cell-mediated rejection, suggesting potential dominance of hypersensitivity mechanisms in these entities.

CONCLUSIONS

These results indicate that, although there is significant molecular similarity between immune checkpoint inhibitor-associated rejection and acute interstitial nephritis, biopsy-based measurement of IFI27 gene expression represents a potential biomarker for differentiating these entities.

Renal Morphology in Coronavirus Disease: A Literature Review

Renal biopsy is useful to better understand the histological pattern of a lesion (glomerular, tubulointerstitial, and vascular) and the pathogenesis that leads to kidney failure. The potential impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the kidneys is still undetermined, and a variety of lesions are seen in the kidney tissue of coronavirus disease patients. This review is based on the morphological findings of patients described in case reports and a series of published cases. A search was conducted on MEDLINE and PubMed of case reports and case series of lesions in the presence of non-critical infection by SARS-CoV-2 published until 15/09/2020. We highlight the potential of the virus directly influencing the damage or the innate and adaptive immune response activating cytokine and procoagulant cascades, in addition to the genetic component triggering glomerular diseases, mainly collapsing focal segmental glomerulosclerosis, tubulointerstitial, and even vascular diseases. Kidney lesions caused by SARS-CoV-2 are frequent and have an impact on morbidity and mortality; thus, studies are needed to assess the morphological kidney changes and their mechanisms and may help define their spectrum and immediate or long-term impact.

Acute Tubulointerstitial Nephritis in Clinical Oncology: A Comprehensive Review

Acute kidney injury in patients who suffer a malignancy is a common complication. Due to its high prevalence and effective treatment, one of the most frequent causes that both oncologists and nephrologists must be aware of is acute tubulointerstitial nephritis (ATIN). ATIN is an immunomediated condition and the hallmark of the disease, with the presence of a tubulointerstitial inflammatory infiltrate in the renal parenchyma. This infiltrate is composed mainly of T lymphocytes that can be accompanied by macrophages, neutrophils, or eosinophils among other cells. One of the major causes is drug-related ATIN, and some antineoplastic treatments have been related to this condition. Worthy of note are the novel immunotherapy treatments aimed at enhancing natural immunity in order to defeat cancer cells. In the context of the immunosuppression status affecting ATIN patients, some pathogen antigens can trigger the development of the disease. Finally, hematological malignancies can also manifest in the kidney leading to ATIN, even at the debut of the disease. In this review, we aim to comprehensively examine differential diagnosis of ATIN in the setting of a neoplastic patient.

Contribution of TFEB-mediated autophagy to tubulointerstitial fibrosis in mice with adenine-induced chronic kidney disease

Autophagy has been implicated in the pathogenesis of chronic kidney disease (CKD). Transcription factor EB (TFEB) is a master controller of autophagy. However, the pathophysiological roles of TFEB in modulating autophagy and tubulointerstitial injury in CKD are unknown. This study aimed to determine whether TFEB-mediated autophagy contributed to the tubulointerstitial injury in mice with CKD. After the mice were treated with an adenine diet (0.2 % adenine) for 8 weeks, the development of CKD was observed to be characterised by increased levels of plasma blood urea nitrogen (BUN), creatinine (Cre), tubulointerstitial inflammation and fibrosis. Immunohistochemical and Western blot analysis further revealed that TFEB and autophagy genes were significantly up-regulated in the kidney of the mice with adenine-induced CKD, and this increase was mostly found in the tubular epithelial cells. Interestingly, a similar expression pattern of TFEB-autophagy genes was observed in tubular epithelial cells in the kidney tissue of patients with immunoglobulin A (IgA) nephropathy. Moreover, a pathogenic role of TFEB in adenine-induced CKD was speculated because the pharmacological activation of TFEB by trehalose failed to protect mice from tubulointerstitial injuries. In the epithelioid clone of normal rat kidney cells (NRK-52E), the activation of TFEB by trehalose increased autophagy induction, cell death and inflammatory cytokine (Interleukin-6, IL-6) release. Collectively, these results suggested that the activation of TFEB-mediated autophagy might cause autophagic cell death and inflammation in tubular epithelial cells, contributing to renal fibrosis in adenine-induced CKD. This study provided novel insights into the pathogenic role of TFEB in CKD associated with a high purine diet.

Kidney involvement and histological findings in two pediatric COVID-19 patients

BACKGROUND

Histological findings of kidney involvement have been rarely reported in pediatric patients with SARS-CoV-2 infection. Here, we describe clinical, laboratory, and histological findings of two pediatric cases with almost exclusive kidney involvement by SARS-CoV-2.

RESULTS

A 10-year-old girl with IgA vasculitis nephritis underwent kidney biopsy, showing diffuse and segmental mesangial-proliferative glomerulonephritis, and steroid therapy was initiated. After the worsening of the clinical picture, including an atypical skin rash, she was diagnosed with SARS-CoV-2. The re-evaluation of initial biopsy showed cytoplasmatic blebs and virus-like particles in tubular cells at electron microscopy. Despite SARS-CoV-2 clearance and the intensification of immunosuppression, no improvement was observed. A second kidney biopsy showed a crescentic glomerulonephritis with sclerosis, while virus-like particles were no longer evident. The second patient was a 12-year-old girl with a 3-week history of weakness and weight loss. Rhinitis was reported the month before. No medications were being taken. Blood and urine analysis revealed elevated serum creatinine, hypouricemia, low molecular weight proteinuria, and glycosuria. A high SARS-CoV-2-IgG titre was detected. Kidney biopsy showed acute tubular-interstitial nephritis. Steroid therapy was started with a complete resolution of kidney involvement.

CONCLUSION

We can speculate that in both cases SARS-CoV-2 played a major role as inflammatory trigger of the kidney damage. Therefore, we suggest investigating the potential kidney damage by SARS-CoV-2 in children. Moreover, SARS-CoV-2 can be included among infectious agents responsible for pediatric acute tubular interstitial nephritis.

Expression pattern of apoptosis-inducing factor in the kidneys of streptozotocin-induced diabetic rats

BACKGROUND

It is believed that tubulo-interstitial fibrosis and atrophy in diabetic patients are directly associated with the progression of chronic kidney disease, CKD. AIF is one of the crucial factors responsible for mitochondrial apoptosis, however, it can also promote cell survival independently from its role in apoptosis, and therefore can be potentially used as a tool in prevention of the onset of CKD in diabetic patients. Our aim was to investigate the significance of AIF expression in the development of CKD by observing the expression of AIF in 2 weeks' and 2 months' kidneys of diabetic rats compared to their controls.

METHODS

Male Sprague-Dawley rats were treated with 55 mg/kg streptozotocin (model of type 1 diabetes mellitus; DM group) or citrate buffer (control). After 2 weeks and 2 months kidney samples were collected and analysed in different renal areas.

RESULTS

Characteristic morphologic changes were found between the 2 months' control and 2 months' diabetic groups. Those changes, including fibrosis and possible replacement of podocytes with connective tissue were mainly present in the glomeruli. AIF expression was seen in the both cortex, and in the collecting ducts of the medulla. Strong intensity of AIF expression was seen in proximal and distal convoluted tubules in both diabetic groups. In the control groups the glomeruli showed no AIF staining but moderate staining was seen in both diabetic groups. Overall, the percentage of AIF positive cells in the glomeruli was the lowest. The greatest rise in cell positivity was displayed from the 2 weeks' control group to 2 weeks' diabetes group (38 %) in glomeruli. The cell positivity of the 2 weeks' diabetic group is significantly reduced to 18 % in the 2 months' diabetic group in glomeruli. A similar pattern was seen in the proximal tubular cells (92 % positivity 2 weeks diabetic groups; 89 % positivity 2 months diabetic groups), as well as in the distal tubules. The highest percentage of AIF positive cells was seen in the collecting ducts, more than 80 % in all groups.

CONCLUSIONS

Our study provides insight into AIF expression pattern during short term diabetes model, confirming possible dual role of AIF, not only in apoptosis but also in cell function and homeostasis, and proving AIF as potential therapeutic target and marker of advancement of CKD.

Pathophysiology and Pathology of Acute Kidney Injury in Patients With COVID-19

Acute kidney injury (AKI) is common among hospitalized patients with Coronavirus Infectious Disease 2019 (COVID-19), with the occurrence of AKI ranging from 0.5% to 80%. The variability in the occurrence of AKI has been attributed to the difference in geographic locations, race/ethnicity, and severity of illness. AKI among hospitalized patients is associated with increased length of stay and in-hospital deaths. Even patients with AKI who survive to hospital discharge are at risk of developing chronic kidney disease or end-stage kidney disease. An improved knowledge of the pathophysiology of AKI in COVID-19 is crucial to mitigate and manage AKI and to improve the survival of patients who developed AKI during COVID-19. The goal of this article is to provide our current understanding of the etiology and the pathophysiology of AKI in the setting of COVID-19.

A novel HNF1B mutation p.R177Q in autosomal dominant tubulointerstitial kidney disease and maturity-onset diabetes of the young type 5: A pedigree-based case report

RATIONALE

Mutations in the hepatocyte nuclear factor-1-beta (HNF1B) gene result in a very variable presentation, including maturity onset diabetes of the young (MODY), renal cysts, renal dysplasia, and autosomal dominant tubulointerstitial kidney disease (ADTKD), which is characterized by tubular damage, renal fibrosis, and progressive renal dysfunction.

PATIENT CONCERNS

A 22-year-old man came to the hospital presenting with hyperglycemia, hyperuricemia and elevated serum creatinine. His urine protein was within the normal range. The ultrasound examination revealed shrunken kidneys with renal cysts. The patient's mother was diagnosed with diabetes mellitus when she was 25 years old. Her laboratory results showed elevated serum creatinine. Her ultrasonography revealed shrunken kidneys with renal cysts and hydronephrosis without kidney stones. The next-generation sequencing revealed that the proband and his mother held the same heterozygous missense mutation (c.530G>A, NM_000458, p.R177Q) in the HNF1B gene. Bioinformatic analyses predicted that the mutation was likely pathogenic.

DIAGNOSIS

The patient and his mother were diagnosed as ADTKD and MODY5 due to HNF1B mutation.

INTERVENTION

The proband was administered metformin at a dose of 500 mg/day.

OUTCOMES

The patient had well-controlled blood glucose levels and a stable renal function at his 12-month follow-up.

LESSONS

We should take into account the diagnoses of ADTKD and MODY5 if patients present with early onset diabetes and multiple renal cysts or evidence of renal tubulointerstitial dysplasia, especially those with negative proteinuria results. Genetic testing helps detect the HNF1B gene mutations.

Long-term Renal Outcome of Biopsy-proven Acute Tubular Necrosis and Acute Interstitial Nephritis

BACKGROUND

Although emerging evidence suggest acute kidney injury (AKI) progress to chronic kidney disease (CKD), long-term renal outcome of AKI still remains unclear. Acute tubular necrosis (ATN) is the most common cause of AKI due to ischemia, toxin or sepsis. Acute interstitial nephritis (AIN), caused by drugs or autoimmune diseases is also increasingly recognized as an important cause of AKI. Unlike glomerular diseases, AKI is usually diagnosed in the clinical context without kidney biopsies, and lack of histology might contribute to this uncertainty.

METHODS

Among 8,769 biopsy series, 253 adults who were histologically diagnosed with ATN and AIN from 1982 to 2018 at five university hospitals were included. Demographic and pathological features that are associated with the development of end stage renal disease (ESRD) were also examined.

RESULTS

Rate of non-recovery of renal function at 6 month was significantly higher in the AIN (ATN vs AIN 49.3 vs 69.4%, P = 0.007) with a 2.71-fold higher risk of non- recovery compared to ATN (95% confidence interval [CI], 1.20-6.47). During the mean follow up of 76.5 ± 91.9 months, ESRD developed in 39.4% of patients with AIN, and 21.5% patients of ATN. The risk of ESRD was significantly higher in AIN (23.05; 95% CI, 2.42-219.53) and also in ATN (12.14; 95% CI, 1.19-24.24) compared to control with non-specific pathology. Older age, female gender, renal function at the time of biopsy and at 6 months, proteinuria and pathological features including interstitial inflammation and fibrosis, tubulitis, vascular lesion were significantly associated with progression to ESRD.

CONCLUSION

Our study demonstrated that patients with biopsy proven ATN and AIN are at high risk of developing ESRD. AIN showed higher rate of non-renal recovery at 6 month than ATN.

Successful Treatment of Non-small-cell Lung Cancer with Atezolizumab Following Tubulointerstitial Nephritis Due to Pembrolizumab

We herein report a 75-year-old man with non-small-cell lung cancer who developed tubulointerstitial nephritis due to pembrolizumab administration. He was successfully treated with atezolizumab following steroid administration. He was initially diagnosed with lung adenocarcinoma (T1bN3M1b, stage IV), with a programmed cell death-ligand 1 tumor proportion score of 25-49%. Although the tumor responded well to pembrolizumab, the drug was discontinued because of the diagnosis of tubulointerstitial nephritis on a renal biopsy. Tubulointerstitial nephritis was treated with 30 mg prednisolone, the dose of which was tapered to and maintained at 5 mg. Following lung cancer progression, atezolizumab was administered, and the tumor responded again. Its efficacy has been sustained for >15 months without recurrence of tubulointerstitial nephritis.