Cyclosporine-induced endoplasmic reticulum stress triggers tubular phenotypic changes and death

Oxysterol-binding protein-like 7 deficiency leads to ER stress-mediated apoptosis in podocytes and proteinuria

Chronic kidney disease (CKD) is associated with renal lipid dysmetabolism among a variety of other pathways. We recently demonstrated that oxysterol-binding protein-like 7 (OSBPL7) modulates the expression and function of ATP-binding cassette subfamily A member 1 (ABCA1) in podocytes, a specialized type of cell essential for kidney filtration. Drugs that target OSBPL7 lead to improved renal outcomes in several experimental models of CKD. However, the role of OSBPL7 in podocyte injury remains unclear. Using mouse models and cellular assays, we investigated the influence of OSBPL7 deficiency on podocytes. We demonstrated that reduced renal OSBPL7 levels as observed in two different models of experimental CKD are linked to increased podocyte apoptosis, primarily mediated by heightened endoplasmic reticulum (ER) stress. Although as expected, the absence of OSBPL7 also resulted in lipid dysregulation (increased lipid droplets and triglycerides content), OSBPL7 deficiency-related lipid dysmetabolism did not contribute to podocyte injury. Similarly, we demonstrated that the decreased autophagic flux we observed in OSBPL7-deficient podocytes was not the mechanistic link between OSBPL7 deficiency and apoptosis. In a complementary zebrafish model, osbpl7 knockdown was sufficient to induce proteinuria and morphological damage to the glomerulus, underscoring its physiological relevance. Our study sheds new light on the mechanistic link between OSBPL7 deficiency and podocyte injury in glomerular diseases associated with CKD, and it strengthens the role of OSBPL7 as a novel therapeutic target.NEW & NOTEWORTHY OSBPL7 and ER stress comprise a central mechanism in glomerular injury. This study highlights a crucial link between OSBPL7 deficiency and ER stress in CKD. OSBPL7 deficiency causes ER stress, leading to podocyte apoptosis. There is a selective effect on lipid homeostasis in that OSBPL7 deficiency affects lipid homeostasis, altering cellular triglyceride but not cholesterol content. The interaction of ER stress and apoptosis supports that ER stress, not reduced autophagy, is the main driver of apoptosis in OSBPL7-deficient podocytes.

Immunosuppression with cyclosporine versus tacrolimus shows distinctive nephrotoxicity profiles within renal compartments

AIM

Calcineurin inhibitors (CNIs) are the backbone for immunosuppression after solid organ transplantation. Although successful in preventing kidney transplant rejection, their nephrotoxic side effects contribute to allograft injury. Renal parenchymal lesions occur for cyclosporine A (CsA) as well as for the currently favored tacrolimus (Tac). We aimed to study whether chronic CsA and Tac exposures, before reaching irreversible nephrotoxic damage, affect renal compartments differentially and whether related pathogenic mechanisms can be identified.

METHODS

CsA and Tac were administered chronically in wild type Wistar rats using osmotic minipumps over 4 weeks. Functional parameters were controlled. Electron microscopy, confocal, and 3D-structured illumination microscopy were used for histopathology. Clinical translatability was tested in human renal biopsies. Standard biochemical, RNA-seq, and proteomic technologies were applied to identify implicated molecular pathways.

RESULTS

Both drugs caused significant albeit differential damage in vasculature and nephron. The glomerular filtration barrier was more affected by Tac than by CsA, showing prominent deteriorations in endothelium and podocytes along with impaired VEGF/VEGFR2 signaling and podocyte-specific gene expression. By contrast, proximal tubule epithelia were more severely affected by CsA than by Tac, revealing lysosomal dysfunction, enhanced apoptosis, impaired proteostasis and oxidative stress. Lesion characteristics were confirmed in human renal biopsies.

CONCLUSION

We conclude that pathogenetic alterations in the renal compartments are specific for either treatment. Considering translation to the clinical setting, CNI choice should reflect individual risk factors for renal vasculature and tubular epithelia. As a step in this direction, we share protein signatures identified from multiomics with potential pathognomonic relevance.

Time-course cross-species transcriptomics reveals conserved hepatotoxicity pathways induced by repeated administration of cyclosporine A

Cyclosporine A (CsA) has shown efficacy against immunity-related diseases despite its toxicity in various organs, including the liver, emphasizing the need to elucidate its underlying hepatotoxicity mechanism. This study aimed to capture the alterations in genome-wide expression over time and the subsequent perturbations of corresponding pathways across species. Six data from humans, mice, and rats, including animal liver tissue, human liver microtissues, and two liver cell lines exposed to CsA toxic dose, were used. The microtissue exposed to CsA for 10 d was analyzed to obtain dynamically differentially expressed genes (DEGs). Single-time points data at 1, 3, 5, 7, and 28 d of different species were used to provide additional evidence. Using liver microtissue-based longitudinal design, DEGs that were consistently up- or down-regulated over time were captured, and the well-known mechanism involved in CsA toxicity was elucidated. Thirty DEGs that consistently changed in longitudinal data were also altered in 28-d rat in-house data with concordant expression. Some genes (e.g. TUBB2A, PLIN2, APOB) showed good concordance with identified DEGs in 1-d and 7-d mouse data. Pathway analysis revealed up-regulations of protein processing, asparagine N-linked glycosylation, and cargo concentration in the endoplasmic reticulum. Furthermore, the down-regulations of pathways related to biological oxidations and metabolite and lipid metabolism were elucidated. These pathways were also enriched in single-time-point data and conserved across species, implying their biological significance and generalizability. Overall, the human organoids-based longitudinal design coupled with cross-species validation provides temporal molecular change tracking, aiding mechanistic elucidation and biologically relevant biomarker discovery.

Oxidative stress in pituitary neuroendocrine tumors: Affecting the tumor microenvironment and becoming a new target for pituitary neuroendocrine tumor therapy

Pituitary adenomas (PAs), or pituitary neuroendocrine tumors (PitNETs), are commonly found in the anterior pituitary gland. Although the majority of PitNETs are benign and stable, several tumors have malignant characteristics. The tumor microenvironment (TME) plays an important role in the process of tumorigenesis and is composed of several types of cells. Various cells in the TME are significantly affected by oxidative stress. It has been reported that immunotherapeutic strategies have good effects in several cancers. However, the clinical potential of immunotherapies in PitNETs has not yet been fully discussed. Oxidative stress can regulate PitNET cells and immune cells in the TME, thus affecting the immune status of the TME of PitNETs. Therefore, modulation of oxidative stress-regulated immune cells using a combination of several agents and the immune system to suppress PitNETs is a promising therapeutic direction. In this review, we systematically analyzed the oxidative stress process within PitNET cells and various immune cells to elucidate the potential value of immunotherapy.

Advances in the interaction between endoplasmic reticulum stress and osteoporosis

The endoplasmic reticulum (ER) is the main site for protein synthesis, folding, and secretion, and accumulation of the unfolded/misfolded proteins in the ER may induce ER stress. ER stress is an important participant in various intracellular signaling pathways. Prolonged- or high-intensity ER stress may induce cell apoptosis. Osteoporosis, characterized by imbalanced bone remodeling, is a global disease caused by many factors, such as ER stress. ER stress stimulates osteoblast apoptosis, increases bone loss, and promotes osteoporosis development. Many factors, such as the drug's adverse effects, metabolic disorders, calcium ion imbalance, bad habits, and aging, have been reported to activate ER stress, resulting in the pathological development of osteoporosis. Increasing evidence shows that ER stress regulates osteogenic differentiation, osteoblast activity, and osteoclast formation and function. Various therapeutic agents have been developed to counteract ER stress and thereby suppress osteoporosis development. Thus, inhibition of ER stress has become a potential target for the therapeutic management of osteoporosis. However, the in-depth understanding of ER stress in the pathogenesis of osteoporosis still needs more effort.

Research progress on endoplasmic reticulum homeostasis in kidney diseases

The endoplasmic reticulum (ER) plays important roles in biosynthetic and metabolic processes, including protein and lipid synthesis, Ca²⁺ homeostasis regulation, and subcellular organelle crosstalk. Dysregulation of ER homeostasis can cause toxic protein accumulation, lipid accumulation, and Ca²⁺ homeostasis disturbance, leading to cell injury and even death. Accumulating evidence indicates that the dysregulation of ER homeostasis promotes the onset and progression of kidney diseases. However, maintaining ER homeostasis through unfolded protein response, ER-associated protein degradation, autophagy or ER-phagy, and crosstalk with other organelles may be potential therapeutic strategies for kidney disorders. In this review, we summarize the recent research progress on the relationship and molecular mechanisms of ER dysfunction in kidney pathologies. In addition, the endogenous protective strategies for ER homeostasis and their potential application for kidney diseases have been discussed.

Role of cyclosporin A in the treatment of kidney disease and nephrotoxicity

The clinical use of cyclosporin A (CsA) has led to significant advances and achievements in the field of transplantation and immune diseases. However, the nephrotoxicity of CsA is a major concern in current immunosuppression regimens. CsA causes abnormal kidney function while treating kidney disease, causing problems for clinicians and patients. Evidence of CsA nephrotoxicity is almost always present in transplant recipients after long-term CsA administration (up to 10 years), and similar phenomena occur with other calcineurin inhibitors. In this review, we summarize the mechanisms and influencing factors of CsA for the treatment of primary nephrotic syndrome. The mechanisms of CsA nephrotoxicity, clinical-pathological features, diagnosis, prevention strategies, and risk factors are summarized. We discuss the correlates and mechanisms of the switch between kidney disease prevention and nephrotoxicity of CsA to better understand the function of CsA in the kidney and to provide a basis for the prevention and treatment of CsA nephrotoxicity.

Palliative Role of Zamzam Water against Cyclosporine-Induced Nephrotoxicity through Modulating Autophagy and Apoptosis Crosstalk

Cyclosporine (CsA) is considered one of the main components of treatment protocols for organ transplantation owing to its immunosuppressive effect. However, its use is very restricted due to its nephrotoxic effect. ZW is an alkaline fluid rich in various trace elements and has a great ability to stimulate antioxidant processes. This study aimed to investigate the possible mitigating effect of ZW on CsA-induced nephrotoxicity and its underlying mechanisms. Forty rats were allocated into four groups (n = 10): a control group, ZW group, cyclosporine A group (injected subcutaneously (SC) with CsA (20 mg/kg/day)), and cyclosporine A+ Zamzam water group (administered CsA (SC) and ZW as their only drinking water (100 mL/cage/day) for 21 days). Exposure to CsA significantly (p < 0.001) increased the serum creatinine level, lipid peroxidation marker level (malondialdehyde; MDA), and the expression of apoptotic markers procaspase-8, caspase-8, caspase- 9, calpain, cytochrome c, caspas-3, P62, and mTOR in renal tissues. Meanwhile, it markedly decreased (p< 0.001) the autophagic markers (AMPK, ULK-I, ATag5, LC3, and Beclin-1), antiapoptotic Bcl-2, and antioxidant enzymes. Moreover, the administration of CsA caused histological alterations in renal tissues. ZW significantly (p < 0.001) reversed all the changes caused by CsA and conclusively achieved a positive outcome in restraining CsA-induced nephrotoxicity, as indicated by the restoration of the histological architecture, improvement of renal function, inhibition of apoptosis, and enhancement of autophagy via the AMPK/mTOR pathway.

Amelioration of Cyclosporine A-Induced Acute Nephrotoxicity by Cordyceps cicadae Mycelia via Mg+2 Reabsorption and the Inhibition of GRP78-IRE1-CHOP Pathway: In Vivo and In Vitro

Fruiting bodies of Cordyceps cicadae (CC) have been reported to have a therapeutic effect in chronic kidney disease. Due to the rare and expensive resources from natural habitats, artificially cultivated mycelia using submerged liquid cultivation of CC (CCM) have been recently developed as an alternative to scarce sources of CC. However, little is known regarding potential protective effects of CCM against cyclosporine A (CsA)-induced acute nephrotoxicity in vivo and in vitro. In this study, male Sprague-Dawley rats were divided into six groups: control, CCM (40 mg and 400 mg/kg, orally), CsA (10 mg/kg, oral gavage), and CsA + CCM (40 mg and 400 mg/kg, orally). At the end of the study on day 8, all rats were sacrificed, and the blood and kidneys retrieved. CsA-induced acute nephrotoxicity was evident by increased levels of blood urea nitrogen (BUN). Levels of the endoplasmic reticulum (ER) resident chaperone glucose regulated protein 78 (GRP 78) were increased significantly in rats with acute nephrotoxicity. BUN and GRP 78 were significantly ameliorated in synchronous oral groups of CCM (40 or 400 mg/kg) plus CsA. Examination of hematoxylin and eosin stained kidney tissues revealed that the combined treatment of CCM slightly improved vacuolization in renal tubules upon CsA-induced damage. CsA-induced down-regulation of protein expression of magnesium ion channel proteins and transient receptor potential melastatin 6 and 7 were abolished by the combined treatment of CCM. CCM has the potential to protect the kidney against CsA-induced nephrotoxicity by reducing magnesium ion wasting, tubular cell damage, and ER stress demonstrated further by human renal proximal tubular epithelial cell line HK-2. Our results contribute to the in-depth understanding of the role of polysaccharides and nucleobases as the main secondary metabolites of CCM in the defense system of renal functions in CsA-induced acute nephrotoxicity.

Involvement of oxidative species in cyclosporine-mediated cholestasis

Cyclosporine is an established medication for the prevention of transplant rejection. However, adverse consequences such as nephrotoxicity, hepatotoxicity, and cholestasis have been associated with prolonged usage. In cyclosporine-induced obstructive and chronic cholestasis, for example, the overproduction of oxidative stress is significantly increased. Additionally, cyclosporine exerts adverse effects on liver function and redox balance responses in treated rats, as evidenced by its increasing levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin while also decreasing the levels of glutathione and NADPH. Cyclosporine binds to cyclophilin to produce its therapeutic effects, and the resulting complex inhibits calcineurin, causing calcium to accumulate in the mitochondria. Accumulating calcium with concomitant mitochondrial abnormalities induces oxidative stress, perturbation in ATP balance, and failure of calcium pumps. Also, cyclosporine-induced phagocyte oxidative stress generation via the interaction of phagocytes with Toll-like receptor-4 has been studied. The adverse effect of cyclosporine may be amplified by the release of mitochondrial DNA, mediated by oxidative stress-induced mitochondrial damage. Given the uncertainty surrounding the mechanism of cyclosporine-induced oxidative stress in cholestasis, we aim to illuminate the involvement of oxidative stress in cyclosporine-mediated cholestasis and also explore possible strategic interventions that may be applied in the future.

The Molecular Quality and Mitochondrial Activity of Porcine Cumulus-Oocyte Complexes Are Affected by Their Exposure to Three Endocrine-Active Compounds under 3D In Vitro Maturation Conditions

Thus far, the potential short- and long-term detrimental effects of a variety of environmental chemicals designated as endocrine-active compounds (EACs) have been found to interfere with histo- and anatomo-physiological functions of the reproductive system in humans and wildlife species. For those reasons, this study sought to examine whether selected EACs, which encompass the fungicide vinclozolin (Vnz), the androgenic anabolic steroid nandrolone (Ndn) and the immunosuppressant cyclosporin A (CsA), affect the developmental competence and molecular quality (MQ) of porcine cumulus–oocyte complexes (COCs) subjected to in vitro maturation (IVM) under 3D culture conditions. The COCs underwent 3D-IVM in the presence of Vnz, Ndn or CsA for 48 h. To explore whether the selected EACs induce internucleosomal DNA fragmentation in cumulus cells (CCs), TUNEL-assisted detection of late apoptotic cells was performed. Additionally, for the detailed evaluation of pro- and antiapoptotic pathways in COCs, apoptosis proteome profiler arrays were used. To determine changes in intracellular metabolism in COCs, comprehensive assessments of mitochondrial ultrastructure and activity were carried out. Moreover, the relative abundances (RAs) of mRNAs transcribed from genes that are involved in scavenging reactive oxygen species (ROS), such as SIRT3 and FOXO3, and intramitochondrial bioenergetic balance, such as ATP synthase subunit (ATP5A1), were ascertained. Finally, to investigate the extent of progression of oocyte maturation, the intraooplasmic levels of cAMP and the RAs of mRNA transcripts encoding regulatory and biocatalytic subunits of a heterodimeric meiosis-promoting factor, termed cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2), were also estimated. The obtained results provide, for the first time, strong evidence that both Vnz and Ndn decrease the developmental competence of oocytes and stimulate apoptosis processes in CCs. The present study is also the first to highlight that Vnz accelerates the maturation process in immature oocytes due to both increased ROS production and the augmented RA of the CCNB1 gene. Furthermore, Vnz was proven to trigger proapoptotic events in CCs by prompting the activity of the FOXO3 transcription factor, which regulates the mitochondrial apoptosis pathway. In turn, Ndn was shown to inhibit oocyte maturation by inducing molecular events that ultimately lead to an increase in the intraooplasmic cAMP concentration. However, due to the simultaneous enhancement of the expression of TNF-β and HSP27 proteins in CCs, Ndn might be responsible for the onset of their neoplastic transformation. Finally, our current investigation is the first to clearly demonstrate that although CsA did not interfere with the nuclear and cytoplasmic maturation of oocytes, by inducing mitophagy in CCs, it disrupted oocyte metabolism, consequently attenuating the parameters related to the MQ of COCs. Summing up, Vnz, Ndn and CsA reduced not only the processes of growth and IVM but also the MQ of porcine COCs, which might make them unsuitable for assisted reproductive technologies (ARTs) such as in vitro fertilization by either gamete co-incubation or intracytoplasmic sperm injection (ICSI) and cloning by somatic cell nuclear transfer (SCNT).

Chronic Allograft Injury

With the incremental improvements in long-term kidney transplant survival, there is renewed focus on what causes failure of the transplanted allograft. Over the past decade, our understanding of the injuries that lead to loss of graft function over time has evolved. Chronic allograft injury includes both immune-mediated and nonimmune-mediated injuries, which may involve the organ donor, the recipient, or both. The targets of injury include the kidney tubular epithelium, the endothelium, and the glomerulus. As a response to injury, there are the expected tissue remodeling and repair processes. However, if inflammation persists, which is not uncommon in the transplant setting, the resulting maladaptive response is matrix deposition and/or fibrosis. This ultimately leads to declining graft function and, finally, failure. With our advancing knowledge of the multiple etiologies and mechanisms, enhanced by more recent cohort studies in humans, there is an opportunity to identify those at greater risk to initiate new strategies to ameliorate the process. Although the most recent studies focus on immune-mediated injuries, there is a critical need to identify both markers of injury and mechanisms of injury. In this review, we highlight the findings of recent studies, highlight the potential therapeutic targets, and identify the continued unmet need for understanding the mechanisms of late graft failure.

TDAG51 induces renal interstitial fibrosis through modulation of TGF-β receptor 1 in chronic kidney disease

Chronic kidney disease (CKD) is characterized by the gradual loss of renal function and is a major public health concern. Risk factors for CKD include hypertension and proteinuria, both of which are associated with endoplasmic reticulum (ER) stress. ER stress-induced TDAG51 protein expression is increased at an early time point in mice with CKD. Based on these findings, wild-type and TDAG51 knock-out (TDKO) mice were used in an angiotensin II/deoxycorticosterone acetate/salt model of CKD. Both wild-type and TDKO mice developed hypertension, increased proteinuria and albuminuria, glomerular injury, and tubular damage. However, TDKO mice were protected from apoptosis and renal interstitial fibrosis. Human proximal tubular cells were used to demonstrate that TDAG51 expression induces apoptosis through a CHOP-dependent mechanism. Further, a mouse model of intrinsic acute kidney injury demonstrated that CHOP is required for ER stress-mediated apoptosis. Renal fibroblasts were used to demonstrate that TGF-β induces collagen production through an IRE1-dependent mechanism; cells treated with a TGF-β receptor 1 inhibitor prevented XBP1 splicing, a downstream consequence of IRE1 activation. Interestingly, TDKO mice express significantly less TGF-β receptor 1, thus, preventing TGF-β-mediated XBP1 splicing. In conclusion, TDAG51 induces apoptosis in the kidney through a CHOP-dependent mechanism, while contributing to renal interstitial fibrosis through a TGF-β-IRE1-XBP1 pathway.

Cyclophilins A and B oppositely regulate renal tubular epithelial cell phenotype

Restoration of kidney tubular epithelium following sublethal injury sequentially involves partial epithelial–mesenchymal transition (pEMT), proliferation, and further redifferentiation into specialized tubule epithelial cells (TECs). Because the immunosuppressant cyclosporine-A produces pEMT in TECs and inhibits the peptidyl-prolyl isomerase (PPIase) activity of cyclophilin (Cyp) proteins, we hypothesized that cyclophilins could regulate TEC phenotype. Here we demonstrate that in cultured TECs, CypA silencing triggers loss of epithelial features and enhances transforming growth factor β (TGFβ)-induced EMT in association with upregulation of epithelial repressors Slug and Snail. This pro-epithelial action of CypA relies on its PPIase activity. By contrast, CypB emerges as an epithelial repressor, because CypB silencing promotes epithelial differentiation, prevents TGFβ-induced EMT, and induces tubular structures in 3D cultures. In addition, in the kidneys of CypB knockout mice subjected to unilateral ureteral obstruction, inflammatory and pro-fibrotic events were attenuated. CypB silencing/knockout leads to Slug, but not Snail, downregulation. CypB support of Slug expression depends on its endoplasmic reticulum location, where it interacts with calreticulin, a calcium-buffering chaperone related to Slug expression. As CypB silencing reduces ionomycin-induced calcium release and Slug upregulation, we suggest that Slug expression may rely on CypB modulation of calreticulin-dependent calcium signaling. In conclusion, this work uncovers new roles for CypA and CypB in modulating TEC plasticity and identifies CypB as a druggable target potentially relevant in promoting kidney repair.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

Calcineurin Inhibitors Nephrotoxicity Prevention Strategies With Stress on Belatacept-Based Rescue Immunotherapy: A Review of the Current Evidence

BACKGROUND

A traditional narrative review was performed to evaluate clinical studies that have examined the clinical implications, risk factors, and prevention of calcineurin inhibitors (CNIs) nephrotoxicity with stress on a belatacept-based rescue regimen.

METHODS

The Cochrane Library, PubMed/MEDLINE, EBSCO (Academic Search Ultimate), ProQuest (Central), and Excerpta Medical databases and Google scholar were searched using the keywords (CNI AND Nephrotoxicity prevention) OR ("Calcineurin inhibitor" AND Nephrotoxicity) OR (Tacrolimus AND Nephrotoxicity) OR (Ciclosporin AND Nephrotoxicity) OR (cyclosporine AND Nephrotoxicity) OR (Belatacept) OR (CNI Conversion) for the period from 1990 to 2020. Fifty-five related articles and reviews were found.

CONCLUSION

A better understanding of the mechanisms underlying calcineurin inhibitor nephrotoxicity could help in the individualization of therapy for and prevention of CNI nephrotoxicity. Identification of high-risk patients for CNI nephrotoxicity before renal transplantation enables better use and selection of immunosuppression with reduced adverse effects and, eventually, successful treatment of the kidney recipients. Belatacept conversion is a good and safe option in patients with deteriorating renal function attributed to CNI nephrotoxicity.

A Review of Traditional Chinese Medicine in Treating Renal Interstitial Fibrosis via Endoplasmic Reticulum Stress-Mediated Apoptosis

Renal interstitial fibrosis (RIF) is the main pathological manifestation of end-stage renal disease. Recent studies have shown that endoplasmic reticulum (ER) stress is involved in the pathogenesis and development of RIF. Traditional Chinese medicine (TCM), as an effective treatment for kidney diseases, can improve kidney damage by affecting the apoptotic signaling pathway mediated by ER stress. This article reviews the apoptotic pathways mediated by ER stress, including the three major signaling pathways of unfolded protein response, the main functions of the transcription factor C/EBP homologous protein. We also present current research on TCM treatment of RIF, focusing on medicines that regulate ER stress. A new understanding of using TCM to treat kidney disease by regulating ER stress will promote clinical application of Chinese medicine and discovery of new drugs for the treatment of RIF.

Cyclosporine A blocks autophagic flux in tubular epithelial cells by impairing TFEB-mediated lysosomal function

Cyclosporine A (CsA) is an immunosuppressor widely used for the prevention of acute rejection during solid organ transplantation. However, severe nephrotoxicity has substantially limited its long‐term usage. Recently, an impaired autophagy pathway was suggested to be involved in the pathogenesis of chronic CsA nephrotoxicity. However, the underlying mechanisms of CsA‐induced autophagy blockade in tubular cells remain unclear. In the present study, we observed that CsA suppressed the activation and expression of transcription factor EB (TFEB) by increasing the activation of mTOR, in turn promoting lysosomal dysfunction and autophagy flux blockade in tubular epithelial cells (TECs) in vivo and in vitro. Restoration of TFEB activation by Torin1‐mediated mTOR inhibition significantly improved lysosomal function and rescued autophagy pathway activity, suppressing TEC injury. In summary, targeting TFEB‐mediated autophagy flux represents a potential therapeutic strategy for CsA‐induced nephrotoxicity.

Astragalus membranaceus and Salvia miltiorrhiza ameliorates cyclosporin A-induced chronic nephrotoxicity through the "gut-kidney axis"

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Astragalus membranaceus and Salvia miltiorrhiza (AS) is an effective prescription that is widely used to treat chronic kidney disease (CKD) clinically in traditional Chinese medicine. Our previous studies have shown that AS can alleviate early CKD through the "gut-kidney axis", but the regulatory role of AS in the "gut-kidney axis" in the middle and late stages of CKD caused by cyclosporin A-induced chronic nephrotoxicity (CICN) has remained unclear.

AIM OF THE STUDY

To explore the protective effect of AS by regulating the intestinal flora to further control the miRNA-mRNA interaction profiles in CICN.

MATERIALS AND METHODS

Thirty-two mice were divided into four groups: Normal (N) (olive oil), Model (M) (CsA, 30 mg kg-1 d-1), AS (CsA + AS, 30 + 8.4 g kg-1 d-1) and FMT-AS (CsA + Faeces of AS group, 30 mg + 10 mL kg-1 d-1). The mice were treated for 6 weeks. Changes in renal function related metabolites were detected, pathological changes in the colon and kidney were observed, and 16S rDNA sequencing was performed on mouse faeces. In addition, miRNA and mRNA sequencing were performed on the kidney to construct differential expression (DE) profiles of the other 3 groups compared with group M. The target mRNAs among the DE miRNAs were then predicted, and an integrated analysis was performed with the DE mRNAs to annotate gene function by KEGG. DE miRNAs and DE mRNAs related to CICN in the overlapping top 20 KEGG pathways were screened and verified.

RESULTS

Eight metabolites that could worsen renal function were increased in group M, accompanied by thickening of the glomerular basement membrane, vacuolar degeneration of renal tubules, and proliferation of collagen fibres, while AS and FMT-AS intervention amended these changes to varying degrees. Simultaneously, intestinal permeability increased, the abundance and diversity of the flora decreased, and the ratio of Firmicum to Bacteroides (F/B) increased in group M. The AS and FMT-AS treatments reversed the flora disorder and increased probiotics producing butyric acid and lactic acid, especially Akkermansia and Lactobacillus, which might regulate the 12 overlapping top 20 KEGG pathways, such as Butanoate metabolism, Tryptophan metabolism and several RF-related pathways, leading to the remission of renal metabolism. Finally, 15 DE miRNAs and 45 DE mRNAs were screened as the therapeutic targets, and the results coincided with the sequencing results.

CONCLUSION

AS could alleviate renal fibrosis and metabolism caused by CICN through the "gut-kidney axis". Probiotics such as Akkermansia and Lactobacillus were the primary driving factors, and the miRNA-mRNA interaction profiles, especially Butanoate metabolism and Tryptophan metabolism, may be an important subsequent response and regulatory mechanism.

Inhibition of oxygen-sensing prolyl hydroxylases increases lipid accumulation in human primary tubular epithelial cells without inducing ER stress

The role of the hypoxia-inducible transcription factor (HIF) pathway in renal lipid metabolism is largely unknown. As HIF stabilizing prolyl hydroxylase (PHD) inhibitors are currently investigated in clinical trials for the treatment of renal anemia, we studied the effects of genetic deletion and pharmacological inhibition of PHDs on renal lipid metabolism in transgenic mice and human primary tubular epithelial cells (hPTEC). Tubular cell-specific deletion of HIF prolyl hydroxylase 2 (Phd2) increased the size of Oil Red-stained lipid droplets in mice. In hPTEC, the PHD inhibitors (PHDi) DMOG and ICA augmented lipid accumulation, which was visualized by Oil Red staining and assessed by microscopy and an infrared imaging system. PHDi-induced lipid accumulation required the exogenous availability of fatty acids and was observed in both proximal and distal hPTEC. PHDi treatment was not associated with structural features of cytotoxicity in contrast to treatment with the immunosuppressant cyclosporine A (CsA). PHDi and CsA differentially upregulated the expression of the lipid droplet-associated genes PLIN2, PLIN4 and HILPDA. Both PHDi and CsA activated AMP-activated protein kinase (AMPK) indicating the initiation of a metabolic stress response. However, only CsA triggered endoplasmic reticulum (ER) stress as determined by the increased mRNA expression of multiple ER stress markers but CsA-induced ER stress was not linked to lipid accumulation. Our data raise the possibility that PHD inhibition may protect tubular cells from toxic free fatty acids by trapping them as triacylglycerides in lipid droplets. This mechanism might contribute to the renoprotective effects of PHDi in experimental kidney diseases.

Endoplasmic reticulum stress signaling in cancer and neurodegenerative disorders: Tools and strategies to understand its complexity

The endoplasmic reticulum (ER) comprises a network of tubules and vesicles that constitutes the largest organelle of the eukaryotic cell. Being the location where most proteins are synthesized and folded, it is crucial for the upkeep of cellular homeostasis. Disturbed ER homeostasis triggers the activation of a conserved molecular machinery, termed the unfolded protein response (UPR), that comprises three major signaling branches, initiated by the protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and the activating transcription factor 6 (ATF6). Given the impact of this intricate signaling network upon an extensive list of cellular processes, including protein turnover and autophagy, ER stress is involved in the onset and progression of multiple diseases, including cancer and neurodegenerative disorders. There is, for this reason, an increasing number of publications focused on characterizing and/or modulating ER stress, which have resulted in a wide array of techniques employed to study ER-related molecular events. This review aims to sum up the essentials on the current knowledge of the molecular biology of endoplasmic reticulum stress, while highlighting the available tools used in studies of this nature.

Cyclosporine A inhibits MRTF-SRF signaling through Na+/K+ ATPase inhibition and actin remodeling

Calcineurin inhibitors (CNI) are the pillars of immunosuppression in transplantation. However, they display a potent nephrotoxicity whose mechanisms remained widely unsolved. We used an untargeted quantitative proteomic approach (iTRAQ technology) to highlight new targets of CNI in renal proximal tubular cells (RPTCs). CNI-treated RPTCs proteome displayed an over-representation of actin-binding proteins with a CNI-specific expression profile. Cyclosporine A (CsA) induced F-actin remodeling and depolymerization, decreased F-actin-stabilizing, polymerization-promoting cofilin (CFL) oligomers, and inhibited the G-actin-regulated serum response factor (SRF) pathway. Inhibition of CFL canonical phosphorylation pathway reproduced CsA effects; however, S3-R, an analogue of the phosphorylation site of CFL prevented the effects of CsA which suggests that CsA acted independently from the canonical CFL regulation. CFL is known to be regulated by the Na+/K+-ATPase. Molecular docking calculations identified two inhibiting sites of CsA on Na+/K+-ATPase and a 23% decrease in Na+/K+-ATPase activity of RPTCs was observed with CsA. Ouabain, a specific inhibitor of Na+/K+-ATPase also reproduced CsA effects on actin organization and SRF activity. Altogether, these results described a new original pathway explaining CsA nephrotoxicity.

Inhibition of the dephosphorylation of eukaryotic initiation factor 2α ameliorates murine experimental pancreatitis

BACKGROUND

Endoplasmic reticulum (ER) stress in the pancreas is closely associated with the development of acute pancreatitis. However, the role of the protein kinase RNA-like ER kinase (PERK) in this disease is not fully understood. We investigated whether an inhibitor of the dephosphorylation of eukaryotic initiation factor 2α, salubrinal, could improve murine experimental pancreatitis through the amelioration of ER stress.

METHODS

Acute pancreatitis was induced by the intraperitoneal administration of cerulein (50 μg/kg) six times at 1-h intervals followed by lipopolysaccharide (10 mg/kg). Salubrinal was administered intraperitoneally immediately after lipopolysaccharide injection and 3 h later. Mice were sacrificed 24 h after the first injection of cerulein, and serum amylase and proinflammatory cytokines were measured. The severity of pancreatitis was evaluated histologically using a scoring system. The expression levels of ER stress-related proteins were evaluated by Western blotting.

RESULTS

The administration of salubrinal significantly attenuated the increase in serum amylase levels and improved histologically assessed pancreatitis. The serum levels of proinflammatory cytokines were significantly suppressed in salubrinal-treated mice, as was the expression of glucose-regulated protein 78, CCAAT/enhancer-binding protein homologous protein, and cleaved caspase-3.

CONCLUSIONS

The amelioration of ER stress through augmentation of the PERK-signaling pathway may be a therapeutic target for the treatment of acute pancreatitis.

Metabolic Pathway of Cyclosporine A and Its Correlation with Nephrotoxicity

Background:

Cyclosporine A (CsA) is widely used for organ transplantation and autoimmune disorders. However, CsA nephrotoxicity is a serious side effect that limits the clinical use of CsA. The metabolism of CsA has a close relationship with this disease in renal-transplant patients. However, the metabolic pathways of CsA and its metabolizing enzymes have rarely been comprehensively reviewed. In this review, we have summarized the specific metabolic profiles of CsA in humans, especially renal-transplant patients. Moreover, the specific metabolizing enzymes and the potential roles that CsA metabolism plays in CsA nephrotoxicity were summarized and discussed.

Methods:

Electronic databases including PubMed, Web of Science, and Scifinder were searched with the keywords "Cyclosporine A and metabolism", and "Cyclosporine A and nephrotoxicity", "Cyclosporine A metabolism and nephrotoxicity". All these studies published until 2018 were included in this review.

Results:

The major metabolic pathways of CsA in humans are hydroxylation and N-demethylation. Normally, these metabolites are relatively less toxic than CsA. However, the metabolism of CsA in the kidneys is much weaker than that in the liver, which explains why CsA is so toxic to the kidneys. CYP3A families, especially CYP3A4 and CYP3A5, play an important role in the biotransformation of CsA. Moreover, increased lines of evidence show that some metabolites (including AM19) associate directly with nephrotoxicity in CsA-treated organ-transplant patients.

Conclusion:

The findings of this review help to further understand the metabolic activities of CsA in renal-transplant patients and cast some light on the mechanisms of CsA nephrotoxicity.

Cyclosporine A binding to COX-2 reveals a novel signaling pathway that activates the IRE1α unfolded protein response sensor

Cyclosporine, a widely used immunosuppressant in organ transplantation and in treatment of various autoimmune diseases, activates the unfolded protein response (UPR), an ER stress coping response. In this study we discovered a new and unanticipated cyclosporine-dependent signaling pathway, with cyclosporine triggering direct activation of the UPR. COX-2 binds to and activates IRE1α, leading to IRE1α splicing of XBP1 mRNA. Molecular interaction and modeling analyses identified a novel interaction site for cyclosporine with COX-2 which caused enhancement of COX-2 enzymatic activity required for activation of the IRE1α branch of the UPR. Cyclosporine-dependent activation of COX-2 and IRE1α in mice indicated that cyclosporine-COX-2-IRE1α signaling pathway was functional in vivo. These findings identify COX-2 as a new IRE1α binding partner and regulator of the IRE1α branch of the UPR pathway, and establishes the mechanism underlying cytotoxicity associated with chronic cyclosporine exposure.

Endoplasmic reticulum stress in pulmonary fibrosis

Endoplasmic reticulum (ER) stress is associated with development and progression of fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). ER stress was first implicated in the pathogenesis of IPF >15 years ago with the discovery of disease-causing mutations in surfactant protein C, which result in a misfolded gene product in type II alveolar epithelial cells (AECs). ER stress and the unfolded protein response (UPR) have been linked to lung fibrosis through regulation of AEC apoptosis, epithelial-mesenchymal transition, myofibroblast differentiation, and M2 macrophage polarization. Although progress has been made in understanding the causes and consequences of ER stress in IPF and a number of chronic fibrotic disorders, further studies are needed to identify key factors that induce ER stress in important cell types and define critical down-stream processes and effector molecules that mediate ER stress-related phenotypes. This review discusses potential causes of ER stress induction in the lungs and current evidence linking ER stress to fibrosis in the context of individual cell types: AECs, fibroblasts, and macrophages. As our understanding of the relationship between ER stress and lung fibrosis continues to evolve, future studies will examine new strategies to modulate UPR pathways for therapeutic benefit.

Activation of Endoplasmic Reticulum Stress in Granulosa Cells from Patients with Polycystic Ovary Syndrome Contributes to Ovarian Fibrosis

Recent studies report the involvement of intra-ovarian factors, such as inflammation and oxidative stress, in the pathophysiology of polycystic ovary syndrome (PCOS), the most common endocrine disorder of reproductive age women. Endoplasmic reticulum (ER) stress is a local factor that affects various cellular events during a broad spectrum of physiological and pathological conditions. It may also be an important determinant of pro-fibrotic remodeling during tissue fibrosis. In the present study, we showed that ER stress was activated in granulosa cells of PCOS patients as well as in a well-established PCOS mouse model. Pharmacological inducers of ER stress, tunicamycin and thapsigargin, were found to increase the expression of pro-fibrotic growth factors, including transforming growth factor (TGF)-β1, in human granulosa cells, and their expression also increased in granulosa cells of PCOS patients. By contrast, treatment of PCOS mice with an ER stress inhibitor, tauroursodeoxycholic acid or BGP-15, decreased interstitial fibrosis and collagen deposition in ovaries, accompanied by a reduction in TGF-β1 expression in granulosa cells. These findings suggest that ER stress in granulosa cells of women with PCOS contributes to the induction of pro-fibrotic growth factors during ovarian fibrosis, and that ER stress may serve as a therapeutic target in PCOS.

Transcriptional regulation of endothelial-to-mesenchymal transition in cardiac fibrosis: role of myocardin-related transcription factor A and activating transcription factor 3

The etiology of cardiac fibrogenesis is quite diverse, but a common feature is the presence of activated fibroblasts. Experimental evidence suggests that a subset of cardiac fibroblasts is derived via transition of vascular endothelial cells into fibroblasts by endothelial-to-mesenchymal transition (EndMT). During EndMT, endothelial cells lose their endothelial characteristics and acquire a mesenchymal phenotype. Molecular mechanisms and the transcriptional mediators controlling EndMT in heart during development or disease remain relatively undefined. Myocardin-related transcription factor A facilitates the transcription of cytoskeletal genes by serum response factor during fibrosis; therefore, its specific role in cardiac EndMT might be of importance. Activation of activating transcription factor 3 (ATF-3) during cardiac EndMT is speculative, since ATF-3 responds to a transforming growth factor β (TGF-β) stimulus and controls the expression of the primary epithelial-to-mesenchymal transition markers Snail, Slug, and Twist. Although the role of TGF-β in EndMT-mediated cardiac fibrosis has been established, targeting of the TGF-β ligand has not proven to be a viable anti-fibrotic strategy owing to the broad functional importance of this ligand. Thus, targeting of downstream transcriptional mediators may be a useful therapeutic approach in attenuating cardiac fibrosis. Here, we discuss some of the transcription factors that may regulate EndMT-mediated cardiac fibrosis and their involvement in type 2 diabetes.

A potential role of the unfolded protein response in post-transplant cancer

Cancer is one of the major causes of mortality in organ transplant patients receiving immunosuppressive regimen based on Cyclosporin A (CsA). Organ transplantation and chronic immunosuppression are typically associated with skin cancers (both squamous cell carcinoma and melanoma) and renal cell carcinoma (RCC). Recent studies have shown that in addition to its immunosuppressive effects, accounted for by the inhibition of calcineurin and the modulation of the transcriptional programme of lymphocytes, CsA also directly stimulates the growth and aggressive behaviour of various cancer cells. Using renal carcinogenesis as an example, we discuss the current evidence for a role of cellular proteostasis, i.e. the regulation of the production, maturation and turnover of proteins in eukaryotic cells, in tumorigenesis arising under conditions of chronic immunosuppression. We present the recent studies showing that CsA induces the unfolded protein response (UPR) in normal and transformed kidney cells. We examine how the UPR might be important, considering in particular the genomic analyses showing the existence of a correlation between the levels of expression of the actors of the UPR, the chaperones of the endoplasmic reticulum (ER) and the aggressiveness of renal carcinoma. The UPR may offer a possible explanation for how immunosuppressive regimens based on CsA promote renal carcinogenesis. We discuss the opportunities offered by this biological knowledge in terms of screening, diagnosis and treatment of post-transplant cancers, and propose possible future translational studies examining the role of tumour proteostasis and the UPR in this context.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Cyclosporine-A induces endoplasmic reticulum stress and influences pro-apoptotic factors in human gingival fibroblasts

Cyclosporine-A (CsA) induces gingival overgrowth. Cyclosporine's anti-apoptotic activity in human gingival fibroblast is due to desensitization of mitochondrial permeability transition pore (MPTP) and augmentation of anti-apoptotic, Bcl2. Alternative mechanisms of apoptosis exist involving enzymes like calcium-dependent Calpain and signaling events related to apoptosis, like Glycogen synthase kinase 3β (GSK3β) and protein kinase A (PKA). Cyclosporine-A in renal tubular cells induces endoplasmic reticulum stress (ER stress) which has not been explored in gingival overgrowth. Hence, this study was carried out to assess the influence of Cyclosporine-on ER stress and on the alternate anti-apoptotic mechanisms. Human gingival fibroblasts were treated with CsA, and expression of ER stress markers, such as binding immunoglobulin protein and CCAAT/enhancer-binding protein homologous protein (CHOP), MPTP, and expression of Calpain & GSK3β /PKA were estimated. The results showed CsA-added fibroblast significantly increasing the expression of Endoplasmic reticulum stress markers. Contrary to usual ER stress outcome of apoptosis, we observed Cyclosporine's anti-apoptotic action in spite of augmented ER stress markers. We conclude that CsA's independent action on different organelles may alter the conventional outcome of ER stress.

Endothelin receptor-specific control of endoplasmic reticulum stress and apoptosis in the kidney

Endothelin-1 (ET-1) promotes renal damage during cardiovascular disease; yet, the molecular mechanisms involved remain unknown. Endoplasmic reticulum (ER) stress, triggered by unfolded protein accumulation in the ER, contributes to apoptosis and organ injury. These studies aimed to determine whether the ET-1 system promotes renal ER stress development in response to tunicamycin. ET_B deficient (ET_B def) or transgenic control (TG-con) rats were used in the presence or absence of ET_A receptor antagonism. Tunicamycin treatment similarly increased cortical ER stress markers in both rat genotypes; however, only ET_B def rats showed a 14-24 fold increase from baseline for medullary GRP78, sXBP-1, and CHOP. Pre-treatment of TG-con rats with the ET_A blocker ABT-627 for 1 week prior to tunicamycin injection significantly reduced the ER stress response in cortex and medulla, and also inhibited renal apoptosis. Pre-treatment with ABT-627 failed to decrease renal ER stress and apoptosis in ET_B def rats. In conclusion, the ET-1 system is important for the development of tunicamycin-induced renal ER stress and apoptosis. ET_A receptor activation induces renal ER stress genes and apoptosis, while functional activation of the ET_B receptor has protective effects. These results highlight targeting the ET_A receptor as a therapeutic approach against ER stress-induced kidney injury.

Cyclosporine-A induces endoplasmic reticulum stress in human gingival fibroblasts - An in vitro study

Drug induced gingival overgrowth is one of the side effects affecting the gingiva due to administration of certain systemic drugs. Cyclosporine A is one such drug which is commonly used in organ transplant conditions. The resultant overgrowth is fibrotic and extensive in nature which could impair patient esthetics and masticatory function. Endoplasmic reticulum stress is a recently identified phenomenon implicated in other fibrotic pathologies such as lung and renal fibrosis. In fact, endoplasmic reticulum stress has been known to play an important role in cyclosporine A induced renal fibrosis. Thus in this study, we sought to identify it's role in drug induced gingival overgrowth.

Klotho mitigates cyclosporine A (CsA)-induced epithelial-mesenchymal transition (EMT) and renal fibrosis in rats

PURPOSE

Klotho deficiency is implicated in various kidney diseases, including renal fibrosis. The aim of this study was to investigate the effect of Klotho administration on epithelial-mesenchymal transition (EMT) and renal fibrosis induced by cyclosporine A (CsA) in rats.

METHODS

CsA-induced renal fibrosis was established by oral administration of CsA (30 mg/kg) to rats on a low-salt diet for 28 days. Klotho was administered to rats by intraperitoneal injection. Renal pathological changes were evaluated by hematoxylin and eosin and Masson's trichrome staining. The EMT response was assessed by measuring the level of TGF-β1, E-cadherin and α-SMA by immunohistochemistry and Western blot.

RESULTS

Administration of CsA for 28 days induced renal damage, decreased Klotho expression and activated the EMT response (demonstrated as increased TGF-β1 and α-SMA expression accompanied by decreased in E-cadherin expression). Treatment with Klotho significantly ameliorated pathological lesions of the kidney by modulating the expression of EMT-associated proteins in the kidney.

CONCLUSIONS

Klotho inhibits CsA-induced EMT and renal fibrosis in rats. Klotho may serve as a therapeutic agent to minimize CsA-induced renal fibrosis.

Stress Response Gene Nupr1 Alleviates Cyclosporin A Nephrotoxicity In Vivo

Acute tubular damage is a major cause of renal failure, especially at the early phase of kidney transplant when ischemia-reperfusion injury and cyclosporin A toxicity may coexist. The mechanisms of the latter are largely unknown. Using an mRNA microarray on microdissected tubules from a rat model of cyclosporin A toxicity to describe the related epithelial-specific transcriptional signature in vivo, we found that cyclosporin A induces pathways dependent on the transcription factor ATF4 and identified nuclear protein transcriptional regulator 1 (Nupr1), a stress response gene induced by ATF4, as the gene most strongly upregulated. Upon cyclosporin A treatment, Nupr1-deficient mice exhibited worse renal tubular lesions than wild-type mice. In primary cultures treated with cyclosporin A, renal tubular cells isolated from Nupr1-deficient mice exhibited more apoptosis and ATP depletion than cells from wild-type mice. Furthermore, cyclosporin A decreased protein synthesis and abolished proliferation in wild-type tubular cells, but only reduced proliferation in Nupr1-deficient cells. Compared with controls, mouse models of ischemia-reperfusion injury, urinary obstruction, and hypertension exhibited upregulated expression of renal NUPR1, and cyclosporin A induced Nupr1 expression in cultured human tubular epithelial cells. Finally, immunohistochemical analysis revealed strong expression of NUPR1 in the nuclei of renal proximal tubules of injured human kidney allografts, but not in those of stable allografts. Taken together, these results suggest that epithelial expression of NUPR1 has a protective role in response to injury after renal transplant and, presumably, in other forms of acute tubular damage.

The epoxyeicosatrienoic acid analog PVPA ameliorates cyclosporine-induced hypertension and renal injury in rats

The introduction of calcineurin inhibitors (CNI) into clinical practice in the late 1970s transformed organ transplantation and led to significant improvement in acute rejection episodes. However, despite their significant clinical utility, the use of these agents is hampered by the development of hypertension and nephrotoxicity, which ultimately lead to end-stage kidney disease and overt cardiovascular outcomes. There are currently no effective agents to treat or prevent these complications. Importantly, CNI-free immunosuppressive regimens lack the overall efficacy of CNI-based treatments and put patients at risk of allograft rejection. Cytochrome P-450 epoxygenase metabolites of arachidonic acid, epoxyeicosatrienoic acids (EETs), have potent vasodilator and antihypertensive properties in addition to many cytoprotective effects, but their effects on CNI-induced nephrotoxicity have not been explored. Here, we show that PVPA, a novel, orally active analog of 14,15-EET, effectively prevents the development of hypertension and ameliorates kidney injury in cyclosporine-treated rats. PVPA treatment reduced proteinuria and renal dysfunction induced by cyclosporine. PVPA inhibited inflammatory cell infiltration into the kidney and decreased renal fibrosis. PVPA also reduced tubular epithelial cell apoptosis, attenuated the generation of reactive oxygen species, and modulated the unfolded protein response that is associated with endoplasmic reticulum stress. Consistent with the in vivo data, PVPA attenuated cyclosporine-induced apoptosis of NRK-52E cells in vitro. These data indicate that the cytochrome P-450/EET system offers a novel therapeutic strategy to treat or prevent CNI-induced nephrotoxicity.

GRP78 and CHOP modulate macrophage apoptosis and the development of bleomycin-induced pulmonary fibrosis

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) have been associated with fibrotic lung disease, although exactly how they modulate this process remains unclear. Here we investigated the role of GRP78, the main UPR regulator, in an experimental model of lung injury and fibrosis. Grp78(+/-) , Chop(-/-) and wild type C57BL6/J mice were exposed to bleomycin by oropharyngeal intubation and lungs were examined at days 7 and 21. We demonstrate here that Grp78(+/-) mice were strongly protected from bleomycin-induced fibrosis, as shown by immunohistochemical analysis, collagen content and lung function measurements. In the inflammatory phase of this model, a reduced number of lung macrophages associated with an increased number of TUNEL-positive cells were observed in Grp78(+/-) mice. Dual immunohistochemical and in situ hybridization experiments showed that the macrophage population from the protected Grp78(+/-) mice was also strongly positive for cleaved caspase-3 and Chop mRNA, respectively. In contrast, the administration of bleomycin to Chop(-/-) mice resulted in increased quasi-static elastance and extracellular matrix deposition associated with an increased number of parenchymal arginase-1-positive macrophages that were negative for cleaved caspase-3. The data presented indicate that the UPR is activated in fibrotic lung tissue and strongly localized to macrophages. GRP78- and CHOP-mediated macrophage apoptosis was found to protect against bleomycin-induced fibrosis. Overall, we demonstrate here that the fibrotic response to bleomycin is dependent on GRP78-mediated events and provides evidence that macrophage polarization and apoptosis may play a role in this process. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Endoplasmic Reticulum Stress Predicts Clinical Response to Cyclosporine Treatment in Primary Membranous Nephropathy

BACKGROUND

Little is known about the endoplasmic reticulum stress (ERS) marker glucose regulated protein 78 (GRP78) and calcineurin in the kidney in primary membranous nephropathy (PMN) and if they could predict post-cyclosporine treatment outcome.

METHODS

This is a retrospective study using a dataset of biopsy-confirmed PMN from Peking Union Medical College Hospital from 1996 to 2014. Seventy-six adult patients treated with cyclosporine as primary immunosuppression for at least 6 months were studied. Immunohistochemistry was used to detect GRP78 and calcineurin in the kidney. Serum calcineurin was assayed by ELISA. Patients were grouped into no-remission (NR, n = 17), partial remission (PR, n = 39), or complete remission (CR, n = 20) at the end of 6 months of treatment.

RESULTS

There was no difference of initial dose of cyclosporine among NR, PR, and CR groups. Kidney calcineurin expression in PMN was significantly increased compared to that in controls (p < 0.0083). The glomerular GRP78 in NR PMN was higher than that in control, CR and PR patients (p < 0.0083). Kidney calcineurin expression and GRP78 expression was positively correlated. However, there were no differences in either serum calcineurin levels or kidney calcineurin expressions among NR, PR or CR groups. There was a negative correlation between serum calcineurin activity and whole kidney calcineurin expression (p = 0.034) or glomerular calcineurin expression (p = 0.007). Neither kidney calcineurin nor GRP78 expression was correlated with proteinuria.

CONCLUSIONS

ERS marker GRP78 in the glomeruli but not serum or kidney calcineurin expression could be a useful marker in PMN to negatively predict the response to cyclosporine treatment at the sixth month.

Unfolded protein response induced by Brefeldin A increases collagen type I levels in hepatic stellate cells through an IRE1α, p38 MAPK and Smad-dependent pathway

Unfolded protein response (UPR) triggered as a consequence of ER stress has been shown to be involved in the development of different pathologies, including fibrotic disorders. In the present paper we explore the role played by UPR on a key fibrogenic parameter in the liver: collagen type I levels in activated hepatic stellate cells (HSC). Using Brefeldin A (BFA) as an ER stress inducer we found that UPR correlated with enhanced mRNA and protein levels of collagen type I in a cell line of immortalized non-tumoral rat HSC. Analysis of the three branches of UPR revealed the activation of IRE1α, PERK and ATF6 in response to BFA, although PERK activation was shown not to be involved in the fibrogenic action of BFA. BFA also activated p38 MAPK in an IRE1α-dependent way and the p38 MAPK inhibitor SB203580 prevented the increase in collagen type I mRNA and protein levels caused by BFA, suggesting the involvement of this kinase on this effect. Analysis of Smad activation showed that phosphorylated nuclear levels of Smad2 and 3 were increased in response to BFA treatment. Inhibition of Smad3 phosphorylation by SIS3 prevented the enhancement of collagen type I levels caused by BFA. Pretreatment with IRE1α and p38 MAPK inhibitors also prevented the increased p-Smad3 accumulation in the nucleus, suggesting an IRE1α-p38 MAPK-Smad pathway to be responsible for the fibrogenic action of BFA on HSC.

Tacrolimus Modulates TGF-β Signaling to Induce Epithelial-Mesenchymal Transition in Human Renal Proximal Tubule Epithelial Cells

Epithelial-mesenchymal transition (EMT), a process which describes the trans-differentiation of epithelial cells into motile mesenchymal cells, is pivotal in stem cell behavior, development and wound healing, as well as contributing to disease processes including fibrosis and cancer progression. Maintenance immunosuppression with calcineurin inhibitors (CNIs) has become routine management for renal transplant patient, but unfortunately the nephrotoxicity of these drugs has been well documented. HK-2 cells were exposed to Tacrolimus (FK506) and EMT markers were assessed by RT PCR and western blot. FK506 effects on TGF-β mRNA were assessed by RT PCR and TGF-β secretion was measured by ELISA. The impact of increased TGF-β secretion on Smad signaling pathways was investigated. The impact of inhibition of TGF-β signaling on EMT processes was assessed by scratch-wound assay. The results presented in this study suggest that FK506 initiates EMT processes in the HK-2 cell line, with altered expression of epithelial and myofibroblast markers evident. Additionally, the study demonstrates that FK506 activation of the TGF-β/ SMAD pathways is an essential step in the EMT process. Overall the results demonstrate that EMT is heavily involved in renal fibrosis associated with CNI nephrotoxicity.

Endoplasmic reticulum stress contributes to arsenic trioxide-induced intrinsic apoptosis in human umbilical and bone marrow mesenchymal stem cells

Arsenic trioxide is an old drug and has been used for a long time in traditional Chinese and Western medicines. However, the cancer treatment of arsenic trioxide has heart and vascular toxicity. The cytotoxic effects of arsenic trioxide and its molecular mechanism in human umbilical mesenchymal stem cells (HUMSC) and human bone marrow-derived mesenchymal stem cells (HMSC-bm) were investigated in this study. Our results showed that arsenic trioxide significantly reduced the viability of HUMSC and HMSC-bm in a concentration- and time-dependent manner. Arsenic trioxide is able to induce apoptotic cell death in HUMSC and HMSC-bm, as shown from the results of morphological examination, flow cytometric analyses, DAPI staining and comet assay. The appearance of arsenic trioxide also led to an increase of intracellular free calcium (Ca(2+) ) concentration and the disruption of mitochondrial membrane potential (ΔΨm). The caspase-9 and caspase-3 activities were time-dependently increased in arsenic trioxide-treated HUMSC and HMSC-bm. In addition, the proteomic analysis and DNA microarray were carried out to investigate the expression level changes of genes and proteins affected by arsenic trioxide treatment in HUMSC. Our results suggest that arsenic trioxide induces a prompt induction of ER stress and mitochondria-modulated apoptosis in HUMSC and HMSC-bm. A framework was proposed for the effect of arsenic trioxide cytotoxicity by targeting ER stress.

Role of endoplasmic reticulum stress in drug-induced toxicity

Drug‐induced toxicity is a key issue for public health because some side effects can be severe and life‐threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug‐induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug‐induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug‐induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models.

Ginsenoside Rg1 protects chronic cyclosporin a nephropathy from tubular cell apoptosis by inhibiting endoplasmic reticulum stress in rats

INTRODUCTION

This study tested the effect of ginsenoside Rg1 (G-Rg1) in cyclosporin A (CsA)-induced endoplasmic reticulum (ER) stress on renal tubular cell apoptosis in a rat model of chronic CsA nephropathy.

MATERIALS AND METHODS

Twenty-two Sprague-Dawley rats were randomized into 3 groups: a control group, a model group (CsA 25 mg/kg per day), and a G-Rg1 treatment group (CsA 25 mg/kg per day and G-Rg1 20 mg/kg per day). We examined the effects of G-Rg1 on histopathology, terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, and expression of glucose-regulated protein 78, CCAAT/enhancer-binding protein homologous protein, and caspase-3 by using Western blot analysis.

RESULTS

G-Rg1 attenuated CsA-induced tubulointerstitial fibrosis and reduced tubular epithelial cell apoptosis as assessed by terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and caspase-3 expression. Compared with the model group, it reduced the expression of glucose-regulated protein 78 and CCAAT/enhancer-binding protein homologous protein (0.12 ± 0.03 vs 0.48 ± 0.05 [P < .01]; 0.55 ± 0.11 vs 1.08 ± 0.07 [P < .05]), respectively.

CONCLUSIONS

G-Rg1 mitigates the progression of chronic CsA nephropathy, at least in part, through inhibition of ER stress-triggered tubular cell apoptosis.

Endoplasmic reticulum stress as a novel target to ameliorate epithelial-to-mesenchymal transition and apoptosis of human peritoneal mesothelial cells

Epithelial-to-mesenchymal transition (EMT) and apoptosis of peritoneal mesothelial cells are known to be the earliest mechanisms of peritoneal fibrosis in peritoneal dialysis (PD). Endoplasmic reticulum (ER) stress with an unfolded protein response is regarded to have a role in the development of organ fibrosis. To investigate the potential role of ER stress as a target to prevent and/or delay the development of peritoneal fibrosis, we examined the effect of ER stress on EMT or apoptosis of human peritoneal mesothelial cells (HPMCs) and elucidated the mechanisms underlying the protective effect of ER stress preconditioning on TGF-β1-induced EMT. ER stress inducers, tunicamycin (TM) and thapsigargin (TG), induced EMT with Smad2/3 phosphorylation, an increased nuclear translocation of β-catenin and Snail expression. Low concentrations of TM and TG did not induce apoptosis within 48 h; however, high concentrations of TM- (>1 ng/ml) and TG- (>1 nM) induced apoptosis at 12 h with a persistent increase in C/EBP homologous protein. TGF-β1 induced EMT and apoptosis in HPMCs, which was ameliorated by taurine-conjugated ursodeoxycholic acid, an ER stress blocker. Interestingly, pre-treatment with TM or TG for 4 h also protected the cells from TGF-β1-induced EMT and apoptosis, demonstrating the role of ER stress as an adaptive response to protect HPMCs from EMT and apoptosis. Peritoneal mesothelial cells isolated from PD patients displayed an increase in GRP78/94, which was correlated with the degree of EMT. These findings suggest that the modulation of ER stress in HPMCs could serve as a novel approach to ameliorate peritoneal damage in PD patients.

Inhibition of the dephosphorylation of eukaryotic initiation factor 2α ameliorates murine experimental colitis

BACKGROUND/AIMS

Endoplasmic reticulum (ER) stress in the intestine is closely associated with the development of inflammatory bowel disease (IBD). However, the role of the protein kinase RNA-like ER kinase in this disease is not fully known. We studied whether an inhibitor of the dephosphorylation of eukaryotic initiation factor 2α, salubrinal, improves murine experimental colitis through the amelioration of ER stress.

METHODS

Colitis was induced by the administration of 3% dextran sulfate sodium (DSS) for 5 days. Mice were injected salubrinal intraperitoneally from the commencement of DSS treatment and were sacrificed on day 10. The severity of colitis was evaluated histologically using a scoring system.Myeloperoxidase activity and the expression of proinflammatory cytokine genes in the colon were analyzed. The expression levels of ER stress-related proteins were evaluated by Western blotting.

RESULTS

The administration of salubrinal significantly attenuated body weight loss and improved colitis, as assessed histologically. The elevation of myeloperoxidase activity and the expression of proinflammatory cytokine genes were suppressed in salubrinal-treated mice. The expression of glucose-regulated protein 78, activating translation factor 4, and heat-shock protein 70 was elevated in mice treated with salubrinal.

CONCLUSION

The amelioration of ER stress may be a therapeutic target for the treatment of IBD.