Cyclophilin A Promotes Inflammation in Acute Kidney Injury but Not in Renal Fibrosis

Cyclosporin A-Based PROTACs Can Deplete Abundant Cellular Cyclophilin A without Suppressing T Cell Activation

Cyclophilin A (CypA), the cellular receptor of the immunosuppressant cyclosporin A (CsA), is an abundant cytosolic protein and is involved in a variety of diseases. For example, CypA supports cancer proliferation and mediates viral infections, such as the human immunodeficiency virus 1 (HIV-1). Here, we present the design of PROTAC (proteolysis targeting chimera) compounds against CypA to induce its intracellular proteolysis and to investigate their effect on immune cells. Interestingly, upon connecting to E3 ligase ligands, both peptide-based low-affinity binders and CsA-based high-affinity binders can degrade CypA at nM concentration in HeLa cells and fibroblast cells. As the immunosuppressive effect of CsA is not directly associated with the binding of CsA to CypA but the inhibition of phosphatase calcineurin by the CypA:CsA complex, we investigated whether a CsA-based PROTAC compound could induce CypA degradation without affecting the activation of immune cells. P3, the most efficient PROTAC compound discovered from this study, could deplete CypA in lymphocytes without affecting cell proliferation and cytokine production. This work demonstrates the feasibility of the PROTAC approach in depleting the abundant cellular protein CypA at low drug dosage without affecting immune cells, allowing us to investigate the potential therapeutic effects associated with the endogenous protein in the future.

Pharmacokinetic Parameters of Recombinant Human Cyclophilin A in Mice

BACKGROUND AND OBJECTIVE

Cyclophilin A (CypA) is an isomerase that functions as a chaperone, housekeeping protein, and cyclosporine A (CsA) ligand. Secreted CypA is a proinflammatory factor, chemoattractant, immune regulator, and factor of antitumor immunity. Experimental data suggest clinical applications of recombinant human CypA (rhCypA) as a biotherapeutic for cancer immunotherapy, stimulation of tissue regeneration, treatment of brain pathologies, and as a supportive treatment for CsA-based therapies. The objective of this study is to analyze the pharmacokinetics of rhCypA in a mouse model.

METHODS

rhCypA was isotope-labeled with 125I and injected intraperitoneally (i.p.) or subcutaneously (s/c) into female mice as a single dose of 100 μg per mouse, equivalent to the estimated first-in-human dose. Analysis of 125I-rhCypA biodistribution and excretion was performed by direct radiometry of the blood, viscera, and urine of mice 0.5-72 h following its administration.

RESULTS

rhCypA showed rapid and even tissue-organ distribution, with the highest tropism (fT = 1.56) and accumulation (maximum concentration, Cmax = 137-167 μg/g) in the kidneys, its primary excretory organ. rhCypA showed the lowest tropism to the bone marrow and the brain (fT = 0.07) but the longest retention in these organs [mean retention time (MRT) = 25-28 h].

CONCLUSION

This study identified promising target organs for rhCypA's potential therapeutic effects. The mode of rhCypA accumulation and retention in organs could be primarily due to the expression of its receptors in them. For the first time, rhCypA was shown to cross the blood-brain barrier and accumulate in the brain. These rhCypA pharmacokinetic data could be extrapolated to humans as preliminary data for possible clinical trials.

Bioinformatics analysis and experimental validation of tumorigenic role of PPIA in gastric cancer

Gastric cancer (GC) is a malignant tumor with high incidence rate and mortality. Due to the lack of effective diagnostic indicators, most patients are diagnosed in late stage and have a poor prognosis. An increasing number of studies have proved that Peptidylprolyl isomerase A (PPIA) can play an oncogene role in various cancer types. However, the precise mechanism of PPIA in GC is still unclear. Herein, we analyzed the mRNA levels of PPIA in pan-cancer. The prognostic value of PPIA on GC was also evaluated using multiple databases. Additionally, the relationship between PPIA expression and clinical factors in GC was also examined. We further confirmed that PPIA expression was not affected by genetic alteration and DNA methylation. Moreover, the upstream regulator miRNA and lncRNA of PPIA were identified, which suggested that LINC10232/miRNA-204-5p/PPIA axis might act as a potential biological pathway in GC. Finally, this study revealed that PPIA was negatively correlated with immune checkpoint expression, immune cell biomarkers, and immune cell infiltration in GC.

Cyclophilins modify their profile depending on the organ or tissue in a murine inflammatory model

Inflammation is the leading subjacent cause of many chronic diseases. Despite several studies in the last decades, the molecular mechanism involving its pathophysiology is not fully known. Recently, the implication of cyclophilins in inflammatory-based diseases has been demonstrated. However, the main role of cyclophilins in these processes remains elusive. Hence, a mouse model of systemic inflammation was used to better understand the relationship between cyclophilins and their tissue distribution. To induce inflammation, mice were fed with high-fat diet for 10 weeks. In these conditions, serum levels of interleukins 2 and 6, tumour necrosis factor-α, interferon-ϒ, and the monocyte chemoattractant protein 1 were elevated, evidencing a systemic inflammatory state. Then, in this inflammatory model, cyclophilins and CD147 profiles in the aorta, liver, and kidney were studied. The results demonstrate that, upon inflammatory conditions, cyclophilins A and C expression levels were increased in the aorta. Cyclophilins A and D were augmented in the liver, meanwhile, cyclophilins B and C were diminished. In the kidney, cyclophilins B and C levels were elevated. Furthermore, CD147 receptor was also increased in the aorta, liver, and kidney. In addition, when cyclophilin A was modulated, serum levels of inflammatory mediators were decreased, indicating a reduction in systemic inflammation. Besides, the expression levels of cyclophilin A and CD147 were also reduced in the aorta and liver, when cyclophilin A was modulated. Therefore, these results suggest that each cyclophilin has a different profile depending on the tissue, under inflammatory conditions.

Sanglifehrin A mitigates multi-organ fibrosis in vivo by inducing secretion of the collagen chaperone cyclophilin B

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis by myofibroblasts have clinical potential as anti-fibrotic agents. Lysine hydroxylation by the prolyl-3-hydroxylase complex, comprised of cartilage associated protein, prolyl 3-hydroxylase 1, and cyclophilin B, is essential for collagen type I crosslinking and formation of stable fibers. Here, we identify the collagen chaperone cyclophilin B as a major cellular target of the macrocyclic natural product sanglifehrin A (SfA) using photo-affinity labeling and chemical proteomics. Our studies reveal a unique mechanism of action in which SfA binding to cyclophilin B in the endoplasmic reticulum (ER) induces the secretion of cyclophilin B to the extracellular space, preventing TGF-β1-activated myofibroblasts from synthesizing collagen type I in vitro without inhibiting collagen type I mRNA transcription or inducing ER stress. In addition, SfA prevents collagen type I secretion without affecting myofibroblast contractility or TGF-β1 signaling. In vivo, we provide chemical, molecular, functional, and translational evidence that SfA mitigates the development of lung and skin fibrosis in mouse models by inducing cyclophilin B secretion, thereby inhibiting collagen synthesis from fibrotic fibroblasts in vivo . Consistent with these findings in preclinical models, SfA reduces collagen type I secretion from fibrotic human lung fibroblasts and precision cut lung slices from patients with idiopathic pulmonary fibrosis, a fatal fibrotic lung disease with limited therapeutic options. Our results identify the primary liganded target of SfA in cells, the collagen chaperone cyclophilin B, as a new mechanistic target for the treatment of organ fibrosis.

Cyclophilin A/CD147 signaling induces the epithelial-to-mesenchymal transition and renal fibrosis in chronic allograft dysfunction by regulating p38 MAPK signaling

Objective

Our study was designed to explore the role of Cyclophilin A (CyPA)/CD147 signaling in renal allograft fibrosis and chronic allograft dysfunction (CAD).

Materials and methods

A rat renal transplant model with significant CAD was successfully achieved. Renal allograft tissues and blood samples were collected. Hematoxylin and eosin, Masson’s, and immunohistochemistry staining were performed. Since CD147 is mainly expressed in the renal tubular epithelial cells, human HK-2 cells were used and intervened by specific concentrations of CyPA, and the total protein and mRNA were extracted. Western blot assay and polymerase chain reaction were performed to explore the protein and mRNA expression of CyPA, CD147, and epithelial-to-mesenchymal transition (EMT)-related biomarkers. SiRNA-CD147 and specific inhibitors of p38 MAPK were used to explore the cellular mechanisms involved in the process.

Results

We have successfully established and validated a 20-week renal transplant CAD model. We observed significant distributed and expressed CyPA and CD147 in the renal allograft fibrotic tissues. We also found a significant expression of CD147 and EMT-related markers in the HK-2 cells stimulated by CyPA. The CD147 siRNA confirmed the previous in vitro results. The selective inhibition of MAPK suggested the notable role of p38 MAPK signaling pathway in the CyP/CD147 signaling involved in renal allograft fibrosis.

Conclusions

Our study reported the positive relationship of CyPA-CD147 signaling with renal allograft dysfunction. The in vitro study suggested that CyPA-CD147 signaling induce the development of the EMT process by p38 MAPK signaling, thus contributing to renal allograft fibrosis and CAD.

Role of MMP-2 and CD147 in kidney fibrosis

Matrix metalloproteinase-2 (MMP-2) and cluster of differentiation 147 (CD147) both play important roles in the development of kidney fibrosis, and CD147 can induce the production and activation of MMP-2. In the early stage of kidney fibrosis, MMP-2 promotes extracellular matrix (ECM) production and accelerates the development of kidney fibrosis, while in the advanced stage, MMP-2 activity decreases, leading to reduced ECM degradation and making it difficult to alleviate kidney fibrosis. The reason for the decrease in MMP-2 activity in the advanced stage is still unclear. On the one hand, it may be related to hypoxia and endocytosis, which lead to changes in the expression of MMP-2-related active regulatory molecules; on the other hand, it may be related to insufficient CD147 function. At present, the specific process by which CD147 is involved in the regulation of MMP-2 activity is not completely clear, and further in-depth studies are needed to clarify the roles of both factors in the pathophysiology of kidney fibrosis.

Determination of reference genes as a quantitative standard for gene expression analysis in mouse mesangial cells stimulated with TGF-β

Reverse transcription-quantitative polymerase chain reaction (RT-PCR) is the gold standard technique for gene expression analysis, but the choice of quantitative reference genes (housekeeping genes, HKG) remains challenging. Identify the best HKG is essential for estimating the expression level of target genes. Therefore, the aim of this study was to determine the best HKG for an in vitro model with mouse mesangial cells (MMCs) stimulated with 5 ng/mL of TGF-β. Five candidates HKG were selected: Actb, Hprt, Gapdh, 18S and Ppia. After quantitative expression, the best combination of these genes was analyzed in silico using six software programs. To validate the results, the best genes were used to normalize the expression levels of fibronectin, vimentin and α-SMA. In silico analysis revealed that Ppia, Gapdh and 18S were the most stable genes between the groups. GenEX software and Spearman's correlation determined Ppia and Gapdh as the best HKG pair, and validation of the HKG by normalizing fibronectin, vimentin and α-SMA were consistent with results from the literature. Our results established the combination of Ppia and Gapdh as the best HKG pair for gene expression analysis by RT-PCR in this in vitro model using MMCs treated with TGF-β.

Exploratory Investigation of the Plasma Proteome Associated with the Endotheliopathy of Trauma

BACKGROUND

The endotheliopathy of trauma (EoT) is associated with increased mortality following injury. Herein, we describe the plasma proteome related to EoT in order to provide insight into the role of the endothelium within the systemic response to trauma.

METHODS

99 subjects requiring the highest level of trauma activation were included in the study. Enzyme-linked immunosorbent assays of endothelial and catecholamine biomarkers were performed on admission plasma samples, as well as untargeted proteome quantification utilizing high-performance liquid chromatography and tandem mass spectrometry.

RESULTS

Plasma endothelial and catecholamine biomarker abundance was elevated in EoT. Patients with EoT (n = 62) had an increased incidence of death within 24 h at 21% compared to 3% for non-EoT (n = 37). Proteomic analysis revealed that 52 out of 290 proteins were differentially expressed between the EoT and non-EoT groups. These proteins are involved in endothelial activation, coagulation, inflammation, and oxidative stress, and include known damage-associated molecular patterns (DAMPs) and intracellular proteins specific to several organs.

CONCLUSIONS

We report a proteomic profile of EoT suggestive of a surge of DAMPs and inflammation driving nonspecific activation of the endothelial, coagulation, and complement systems with subsequent end-organ damage and poor clinical outcome. These findings support the utility of EoT as an index of cellular injury and delineate protein candidates for therapeutic intervention.

Mice with Established Diabetes Show Increased Susceptibility to Renal Ischemia/Reperfusion Injury: Protection by Blockade of Jnk or Syk Signaling Pathways

Patients with diabetes are at an increased risk for acute kidney injury (AKI) after renal ischemia/reperfusion injury (IRI). However, there is a lack preclinical models of IRI in established diabetes. The current study characterized renal IRI in mice with established diabetes and investigated potential therapies. Diabetes was induced in C57BL/6J mice by low-dose streptozotocin injection. After 7 weeks of sustained diabetes, mice underwent 13 minutes of bilateral renal ischemia and were euthanized after 24 hours of reperfusion. Age-matched, nondiabetic controls underwent the same surgical procedure. Renal IRI induced two- and sevenfold increases in plasma creatinine level in nondiabetic and diabetic mice, respectively (P < 0.001). Kidney damage, as indicated by histologic damage, tubular cell death, tubular damage markers, and inflammation, was more severe in the diabetic IRI group. The diabetic IRI group showed greater accumulation of spleen tyrosine kinase (Syk)-expressing cells, and increased c-Jun N-terminal kinase (Jnk) signaling in tubules compared to nondiabetic IRI. Prophylactic treatment with a Jnk or Syk inhibitor substantially reduced the severity of AKI in the diabetic IRI model, with differential effects on neutrophil infiltration and Jnk activation. In conclusion, established diabetes predisposed mice to renal IRI-induced AKI. Two distinct proinflammatory pathways, JNK and SYK, were identified as potential therapeutic targets for anticipated AKI in patients with diabetes.

Tacrolimus ameliorates podocyte injury by restoring FK506 binding protein 12 (FKBP12) at actin cytoskeleton

FKBP12 was identified as a binding protein of tacrolimus (Tac). Tac binds to FKBP12 and exhibits immunosuppressive effects in T cells. Although it is reported that Tac treatment directly ameliorates the dysfunction of the podocyte in nephrotic syndrome, the precise pharmacological mechanism of Tac is not well understood yet. It is also known that FKBP12 functions independently of Tac. However, the localization and the physiological function of FKBP12 are not well elucidated. In this study, we observed that FKBP12 is highly expressed in glomeruli, and the FKBP12 in glomeruli is restricted in podocytes. FKBP12 in cultured podocytes was expressed along the actin cytoskeleton and associated with filamentous actin (F-actin). FKBP12 interacted with the actin-associated proteins 14-3-3 and synaptopodin. RNA silencing for FKBP12 reduced 14-3-3 expression, F-actin staining, and process formation in cultured podocytes. FKBP12 expression was decreased in the nephrotic model caused by adriamycin (ADR) and the cultured podocyte treated with ADR. The process formation was deteriorated in the podocytes treated with ADR. Tac treatment ameliorated these decreases. Tac treatment to the normal cells increased the expression of FKBP12 at F-actin in processes and enhanced process formation. Tac enhanced the interaction of FKBP12 with synaptopodin. These observations suggested that FKBP12 at actin cytoskeleton participates in the maintenance of processes, and Tac treatment ameliorates podocyte injury by restoring FKBP12 at actin cytoskeleton.

The Role of Cyclophilins in Inflammatory Bowel Disease and Colorectal Cancer

Cyclophilins (Cyps) is a kind of ubiquitous protein family in organisms, which has biological functions such as promoting intracellular protein folding and participating in the pathological processes of inflammation and tumor. Inflammatory bowel disease (IBD) and colorectal cancer (CRC) are two common intestinal diseases, but the etiology and pathogenesis of these two diseases are still unclear. IBD and CRC are closely associated, IBD has always been considered as one of the main risks of CRC. However, the role of Cyps in these two related intestinal diseases is rarely studied and reported. In this review, the expression of CypA, CypB and CypD in IBD, especially ulcerative colitis (UC), and CRC, their relationship with the development of these two intestinal diseases, as well as the possible pathogenesis, were briefly summarized, so as to provide modest reference for clinical researches and treatments in future.

JUN Amino-Terminal Kinase 1 Signaling in the Proximal Tubule Causes Cell Death and Acute Renal Failure in Rat and Mouse Models of Renal Ischemia/Reperfusion Injury

Activation of the JUN amino-terminal kinase (JNK) pathway is prominent in most forms of acute and progressive tubulointerstitial damage, including acute renal ischemia/reperfusion injury (IRI). Two forms of JNK, JNK1 and JNK2, are expressed in the kidney. Systemic administration of pan-JNK inhibitors suppresses renal IRI; however, the contribution of JNK1 versus JNK2, and the specific role of JNK activation in the proximal tubule in IRI, remains unknown. These questions were addressed in rat and mouse models of acute bilateral renal IRI. Administration of the JNK inhibitor, CC-930, substantially reduced the severity of renal failure, tubular damage, and inflammation at 24 hours in a rat IRI model. Additionally, Jnk1^-/- mice, but not Jnk2^-/- mice, were shown to be significantly protected against acute renal failure, tubular damage, and inflammation in the IRI model. Furthermore, mice with conditional Jnk1 deletion in the proximal tubule also showed considerable protection from IRI-induced renal failure, tubular damage, and inflammation. Finally, primary cultures of Jnk1^-/-, but not Jnk2^-/-, tubular epithelial cells were protected from oxidant-induced cell death, in association with preventing phosphorylation of proteins (receptor interacting serine/threonine kinase 3 and mixed lineage kinase domain-like pseudokinase) in the necroptosis pathway. In conclusion, JNK1, but not JNK2, plays a specific role in IRI-induced cell death in the proximal tubule, leading to acute renal failure.

Cyclophilin Inhibition Protects Against Experimental Acute Kidney Injury and Renal Interstitial Fibrosis

Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease.