Global gene expression analysis reveals a role for the alpha 1 integrin in renal pathogenesis.

Kidney fibrosis is the hallmark of most types of progressive kidney disease, including the genetic disorder Alport's syndrome. We undertook gene expression analysis in Alport's syndrome mouse kidneys using microchip arrays to characterize the development of fibrosis. In addition to matrix and matrix-remodeling genes, consistent with interstitial fibrosis, macrophage-related genes show elevated expression levels in Alport's syndrome kidneys. Immunohistochemical analysis of kidney sections illustrated that macrophages as well as myofibroblasts accumulate in the tubular interstitium. Deletion of alpha(1) integrin results in decreased accumulation of both myofibroblasts and macrophages in the tubular interstitium in Alport's syndrome mice and delays disease progression. Transforming growth factor beta antagonism, although reducing interstitial fibrosis, does not limit macrophage accumulation in the tubular interstitium and disease progression. In this study, we identified previously overlooked inflammatory events that occur in the tubulointerstitial region. We propose that in addition to the previously suggested role for the alpha(1)beta(1) integrin in mesangial expansion and abnormal laminin deposition, this integrin may be critical for monocyte accumulation that, in turn, may lead directly to renal failure. Our gene expression and immunohistochemical data indicate that macrophage accumulation is dependent on alpha(1) integrin expression on the macrophage cell surface and that anti-alpha(1) integrin strategies may be employed as therapeutics in the treatment of chronic inflammatory and fibrotic diseases.     

Phosphodiesterase inhibitor ameliorates senescent changes of renal interstitial pericytes in aging kidney

Pericytes are mesenchymal cells that surround endothelial cells, playing a crucial role in angiogenesis and vessel maturation. Additionally, they are associated with interstitial fibrosis as a major contributor to renal myofibroblasts. In this study, we aim to investigate whether the phosphodiesterase inhibitor, pentoxifylline (PTX), can ameliorate aging-related functional and histological deterioration in the kidney. We subjected aging C57BL/6 mice, dividing into young, aging, and PTX-treated aging groups. Renal function, albuminuria, and histological changes were assessed. Interstitial pericytes were assessed by immunohistochemistry analysis. We examined changes in pericytes in elderly patients using human kidney tissue obtained from healthy kidney donors for kidney transplantation. In vitro experiments with human pericytes and endothelial cells were performed. Aging mice exhibited declined renal function, increased albuminuria, and aging-related histological changes including mesangial expansion and tubulointerstitial fibrosis. Notably, number of pericytes declined in aging kidneys, and myofibroblasts increased. PTX treatment ameliorated albuminuria, histological alterations, and microvascular rarefaction, as well as modulated angiopoietin expression. In vitro experiments showed PTX reduced cellular senescence and inflammation. Human kidney analysis confirmed similar pericyte changes in aging kidneys. The phosphodiesterase inhibitor, PTX preserved microvascular density and improved renal interstitial fibrosis and inflammation in aging mice kidneys. These protective effects were suggested to be associated with the amelioration of pericytes reduction and the transition to myofibroblasts. Additionally, the upregulation of angiopoietin-1 expression may exert potential impacts. To the best of our knowledge, this is the first report on the changes in renal interstitial pericytes in aging human kidneys.     

Autophagy in FOXD1 stroma-derived cells regulates renal fibrosis through TGF-β and NLRP3 inflammasome pathway

Renal fibrosis is the final common pathway of various renal injuries and it leads to chronic kidney disease. Recent studies reported that FOXD1-lineage pericyte plays a critical role in tubulointerstitial fibrosis (TIF). However the regulatory mechanisms remain unclear. Autophagy is a cellular process of degradation of damaged cytoplasmic components that regulates cell death and proliferation. To investigate the role of autophagy in FOXD1-lineage pericytes on renal TIF, we generated the FOXD1-lineage stromal cell-specific Atg7 deletion (Atg7^△FOXD1) mice. FOXD1-lineage stromal cell-specific Atg7 deletion enhanced renal TIF through Smad-dependent transforming growth factor (TGF)-β signaling after unilateral ureteral obstruction (UUO). FOXD1-lineage stromal cell-specific Atg7 deletion increased the accumulation of interstitial myofibroblasts and enhanced the differentiation of pericytes into myofibroblasts after UUO. Peritubular capillary rarefaction was accelerated in Atg7^△FOXD1 mice after UUO. Atg7^△FOXD1 mice increased the accumulation of SQSTM1/p62-positive aggregates in the obstructed kidney and resulted in increased expression of NLRP3 inflammasome, interleukin (IL) 1-β and caspase-1 signaling pathway, which enhanced apoptosis of interstitial cells after UUO. In summary, our data showed that autophagy in FOXD1-lineage stromal cells plays a protective role in renal TIF through regulating the Smad4 dependent TGF-β an NLRP3 inflammasome signaling pathway.     

TLR-2/TLR-4 TREM-1 Signaling Pathway Is Dispensable in Inflammatory Myeloid Cells during Sterile Kidney Injury

Inflammatory macrophages are abundant in kidney disease, stimulating repair, or driving chronic inflammation and fibrosis. Damage associated molecules (DAMPs), released from injured cells engage pattern recognition receptors (PRRs) on macrophages, contributing to activation. Understanding mechanisms of macrophage activation during kidney injury may lead to strategies to alleviate chronic disease. We identified Triggering-Receptor-in-Myeloid-cells (TREM)-1, a regulator of TLR signaling, as highly upregulated in kidney inflammatory macrophages and tested the roles of these receptors in macrophage activation and kidney disease. Kidney DAMPs activated macrophages in vitro, independently of TREM-1, but partially dependent on TLR-2/−4, MyD88. In two models of progressive interstitial kidney disease, TREM-1 blockade had no impact on disease or macrophage activation in vivo, but TLR-2/−4, or MyD88 deficiency was anti-inflammatory and anti-fibrotic. When MyD88 was mutated only in the myeloid lineage, however, there was no bearing on macrophage activation or disease progression. Instead, TLR-2/−4 or MyD88 deficiency reduced activation of mesenchyme lineage cells resulting in reduced inflammation and fibrosis, indicating that these pathways play dominant roles in activation of myofibroblasts but not macrophages. To conclude, TREM-1, TLR2/4 and MyD88 signaling pathways are redundant in myeloid cell activation in kidney injury, but the latter appear to regulate activation of mesenchymal cells.     

Toll-like receptor signaling and SIGIRR in renal fibrosis upon unilateral ureteral obstruction

Innate immune activation via IL-1R or Toll-like receptors (TLR) contibutes to acute kidney injury but its role in tissue remodeling during chronic kidney disease is unclear. SIGIRR is an inhibitor of TLR-induced cytokine and chemokine expression in intrarenal immune cells, therefore, we hypothesized that Sigirr-deficiency would aggravate postobstructive renal fibrosis. The expression of TLRs as well as endogenous TLR agonists increased within six days after UUO in obstructed compared to unobstructed kidneys while SIGIRR itself was downregulated by day 10. However, lack of SIGIRR did not affect the intrarenal mRNA expression of proinflammatory and profibrotic mediators as well as the numbers of intrarenal macrophages and T cells or morphometric markers of tubular atrophy and interstitial fibrosis. Because SIGIRR is known to block TLR/IL-1R signaling at the level of the intracellular adaptor molecule MyD88 UUO experiments were also performed in mice deficient for either MyD88, TLR2 or TLR9. After UUO there was no significant change of tubular interstitial damage and interstitial fibrosis in neither of these mice compared to wildtype counterparts. Additional in-vitro studies with CD90+ renal fibroblasts revealed that TLR agonists induce the expression of IL-6 and MCP-1/CCL2 but not of TGF-β, collagen-1α or smooth muscle actin. Together, postobstructive renal interstitial fibrosis and tubular atrophy develop independent of SIGIRR, TLR2, TLR9, and MyD88. These data argue against a significant role of these molecules in renal fibrosis.     

B lymphocytes in renal interstitial fibrosis

Fibrosis is defined as an excessive deposition of extracellular matrix (ECM), which leads to the destruction of organ structure and impairment of organ function. Fibrosis occurs not only in kidney but also in lung, liver, heart, and skin. Common pathways of fibrosis are thought to exist. Renal interstitial fibrosis is a complex process that involves multiple molecular signaling and multiple cellular components, in which B cells appear to be one of the emerging important players. B cells may affect fibrosis through cytokine production and through interaction with other cells including fibroblasts, macrophages and T cells. This review summarizes recent research findings of B cells in fibrosis and provides an insight of how the future therapeutics of fibrosis could be developed from a B-cell point of view.     

The cellular and signalling alterations conducted by TGF-β contributing to renal fibrosis

Renal fibrosis is a common irreversible process of chronic kidney disease (CKD) characterized by uncontrolled deposits of extracellular matrix, replacement of cellular parenchyma and progressive loss of renal function. Recent evidence suggests that a series of phenotypic transformations of resident renal cells are responsible for the formation of interstitial myofibroblasts, cells that play a key role in the fibrotic process. In the renal glomerulus transformation of mesangial cells to myofibroblasts is an event that orchestrates glomerulosclerosis and the participation of other cells types has also been suggested. Recent findings clarify the role of tubular epithelium in mediating the generation of ECM producing cells in the tubule interstitium. Also, crosstalk between injured cells and myofibroblasts for amplification of the fibrogenic cascade in CKD occurs. The crucial conductor of these changes in the kidney is the transforming growth factor-β (TGF-β). Thus, this review focuses on the control of this cytokines signaling mechanisms and their dysregulation in CKD. Further, some of the promising interventional alternatives targeting TGF-β are also discussed.     

Sphingosine kinase 2 cooperating with Fyn promotes kidney fibroblast activation and fibrosis via STAT3 and AKT

Sphingosine kinases (Sphks) are the rate-limiting enzymes in the conversion of sphingosine to biologically active sphingosine-1-phosphate. The present study aimed to determine the role of Sphk2 and its downstream targets in renal fibroblast activation and interstitial fibrosis. In the kidney interstitium of patients with renal fibrosis, Sphk2^high-expressing cells (mainly interstitial fibroblasts) were significantly elevated and highly correlated with disease progression in patients. In a murine model of renal interstitial fibrosis, Sphk2 was upregulated in the kidney of wild-type mice in response to disease progression. Importantly, Sphk2-knockout (KO) mice exhibited significantly lower levels of extracellular matrix (ECM) production and a suppressed inflammatory response in the kidney tissues, compared to those in their wild-type counterparts, whereas the expression of TGF-β1 was unaffected. TGF-β1 effectively upregulated Sphk2 expression in the renal interstitial fibroblast line, NRK-49F, independent of canonical Smad signaling activation. Furthermore, siRNA-mediated Sphk2 knockdown or suppression of Sphk2 activity by ABC294640 exposure effectively attenuated AKT and STAT3 activation and ECM production, but had no effects on Smad2 and Smad3 activation. Sphk2 phosphorylated Fyn to activate downstream STAT3 and AKT, thereby promoting ECM synthesis. Therefore, our findings indicate that targeting Sphk2-Fyn-STAT3/AKT signaling pathway may be a novel therapeutic approach for renal fibrosis.     

Inhibition of mTOR signaling with rapamycin attenuates renal hypertrophy in the early diabetic mice

Early diabetic nephropathy is characterized by renal hypertrophy that is mainly due to proximal tubular hypertrophy. Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase, and its signaling has been reported to regulate protein synthesis and cellular growth, specifically, hypertrophy. Therefore, we examined the effect of mTOR signaling on diabetic renal hypertrophy by using the specific inhibitor for mTOR, rapamycin. Ten days after streptozotocin-induced diabetes, mice showed kidney hypertrophy with increases in the phosphorylation of p70S6kinase and the expression of cyclin kinase inhibitors, p21(Cip1) and p27(Kip1), in the kidneys. The intraperitoneal injection of rapamycin (2 mg/kg/day) markedly attenuated the enhanced phosphorylation of p70S6kinase, the increment of cyclin-dependent kinase inhibitors, and renal enlargement without any changes of clinical parameters, including blood glucose, blood pressure, and food intake. Overexpression of a constitutive active form of p70S6kinase resulted in increased cell size of cultured mouse proximal tubule cells; thus, activation of p70S6kinase causes hypertrophy of proximal tubular cells. Our findings suggest that activation of mTOR signaling causes renal hypertrophy at the early stage of diabetes.     

Overexpression of Heme Oxygenase-1 Prevents Renal Interstitial Inflammation and Fibrosis Induced by Unilateral Ureter Obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases. Many studies have demonstrated that heme oxygenase-1 (HO-1) is involved in diverse biological processes as a cytoprotective molecule, including anti-inflammatory, anti-oxidant, anti-apoptotic, antiproliferative, and immunomodulatory effects. However, the mechanisms of HO-1 prevention in renal interstitial fibrosis remain unknown. In this study, HO-1 transgenic (TG) mice were employed to investigate the effect of HO-1 on renal fibrosis using a unilateral ureter obstruction (UUO) model and to explore the potential mechanisms. We found that HO-1 was adaptively upregulated in kidneys of both TG and wild type (WT) mice after UUO. The levels of HO-1 mRNA and protein were increased in TG mice compared with WT mice under normal conditions. HO-1 expression was further enhanced after UUO and remained high during the entire experimental process. Renal interstitial fibrosis in the TG group was significantly attenuated compared with that in the WT group after UUO. Moreover, overexpression of HO-1 inhibited the loss of peritubular capillaries. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by HO-1 overexpression. Furthermore, HO-1 restrained tubulointerstitial infiltration of macrophages and regulated the secretion of inflammatory cytokines in UUO mice. We also found that high expression of HO-1 inhibited reactivation of Wnt/β-catenin signaling, which could play a crucial role in attenuating renal fibrosis. In conclusion, these data suggest that HO-1 prevents renal tubulointerstitial fibrosis possibly by regulating the inflammatory response and Wnt/β-catenin signaling. This study provides evidence that augmentation of HO-1 levels may be a therapeutic strategy against renal interstitial fibrosis.     

Blockade of CD38 diminishes lipopolysaccharide-induced macrophage classical activation and acute kidney injury involving NF-κB signaling suppression

The CD38, possessing ADP-ribosyl cyclase (ADPR-cyclase) and cyclic ADP-ribose hydrolase (cADPR-hydrolase), is able to regulate a variety of cellular activities. However, the role and mechanisms for CD38 in macrophage activation and sepsis-induced acute kidney injury (AKI) remain to be determined. Here we report that in cultured macrophages, Lipopolysaccharide (LPS) could upregulate CD38 expression in time and dose dependent manner. Knocking down or blockade of CD38 in macrophages could inhibit LPS-induced macrophage M1 polarization accompanied by diminished NF-κB signaling activation. In mouse model with LPS-induced acute kidney injury, blocking CD38 with quercetin could significantly relieve kidney dysfunction, kidney pathological changes as well as inflammatory cell accumulation. Similar to those in the cultured cells, quercetin could inhibit macrophage M1 polarization and NF-κB signaling activation in macrophages from kidneys and spleens in mice after LPS injection. Together, these results demonstrate that CD38 mediates LPS-induced macrophage activation and AKI, which may be treated as a therapeutic target for sepsis-induced AKI in patients.     

CCR2 Regulates the Uptake of Bone Marrow-Derived Fibroblasts in Renal Fibrosis

Recent studies have shown that bone marrow-derived fibroblasts contribute significantly to the pathogenesis of renal fibrosis. However, the molecular mechanisms underlying the recruitment of bone marrow-derived fibroblasts into the kidney are incompletely understood. Bone marrow-derived fibroblasts express the chemokine receptor - CCR2. In this study, we tested the hypothesis that CCR2 participates in the recruitment of fibroblasts into the kidney during the development of renal fibrosis. Bone marrow-derived collagen-expressing GFP⁺ fibroblasts were detected in the obstructed kidneys of chimeric mice transplanted with donor bone marrow from collagen α1(I)-GFP reporter mice. These bone marrow-derived fibroblasts expressed PDGFR-β and CCR2. CCR2 knockout mice accumulated significantly fewer bone marrow-derived fibroblast precursors expressing the hematopoietic marker-CD45 and the mesenchymal markers-PDGFR-β or procollagen I in the obstructed kidneys compared with wild-type mice. Furthermore, CCR2 knockout mice displayed fewer bone marrow-derived myofibroblasts and expressed less α-SMA or FSP-1 in the obstructed kidneys compared with wild-type mice. Consistent with these findings, genetic deletion of CCR2 inhibited total collagen deposition and suppressed expression of collagen I and fibronectin. Moreover, genetic deletion of CCR2 inhibits MCP-1 and CXCL16 gene expression associated with a reduction of inflammatory cytokine expression and macrophage infiltration, suggesting a linear interaction between two chemokines/ligand receptors in tubular epithelial cells. Taken together, our results demonstrate that CCR2 signaling plays an important role in the pathogenesis of renal fibrosis through regulation of bone marrow-derived fibroblasts. These data suggest that inhibition of CCR2 signaling could constitute a novel therapeutic approach for fibrotic kidney disease.     

Akt2 Is Involved in Loss of Epithelial Cells and Renal Fibrosis following Unilateral Ureteral Obstruction

Obstructive nephropathy is an aggressive form of chronic kidney disease (CKD), which is characterized by an epithelial-to-mesenchymal transition (EMT) and interstitial fibrosis. However, the molecular mechanisms of EMT and fibrosis are complex and not fully understood. In this study, we investigated the contribution of Akt2 to experimental renal EMT and fibrosis using the well-established model of unilateral ureteral obstruction (UUO). We found that Akt2 and phosphor (p)-Akt protein levels were increased in the obstructed kidneys. UUO induced activation of transforming growth factor-β1 (TGF-β1) signaling. Importantly, knockout of Akt2 suppressed UUO-induced EMT, kidney fibrosis, increased GSK3β activity, and decreased expression of Snail and β-catenin. Inhibition of GSK3β with LiCl (the inhibitor of GSK3β) increased the expression of Snail and β-catenin in cultured kidney epithelial cells. Our findings suggest that Akt2 partially contributes to interstitial fibrosis following UUO and that inhibition of this signaling pathway may provide a novel approach of prevent progression of renal fibrosis.     

Leptin induces macrophage lipid body formation by a phosphatidylinositol 3-kinase- and mammalian target of rapamycin-dependent mechanism

Leptin is an adipocyte-derived hormone/cytokine that links nutritional status with neuroendocrine and immune functions. Lipid bodies (lipid droplets) are emerging as dynamic organelles with roles in lipid metabolism and inflammation. Here we investigated the roles of leptin in signaling pathways involved in cytoplasmic lipid body biogenesis and leukotriene B(4) synthesis in macrophages. Our results demonstrated that leptin directly activated macrophages and induced the formation of adipose differentiation-related protein-enriched lipid bodies. Newly formed lipid bodies were sites of 5-lipoxygenase localization and correlated with an enhanced capacity of leukotriene B(4) production. We demonstrated that leptin-induced macrophage activation was dependent on phosphatidylinositol 3-kinase (PI3K) activity, since the lipid body formation was inhibited by LY294002 and was absent in the PI3K knock-out mice. Leptin induces phosphorylation of p70(S6K) and 4EBP1 key downstream signaling intermediates of the mammalian target of rapamycin (mTOR) pathway in a rapamycin-sensitive mechanism. The mTOR inhibitor, rapamycin, inhibited leptin-induced lipid body formation, both in vivo and in vitro. In addition, rapamycin inhibited leptin-induced adipose differentiation-related protein accumulation in macrophages and lipid body-dependent leukotriene synthesis, demonstrating a key role for mTOR in lipid body biogenesis and function. Our results establish PI3K/mTOR as an important signaling pathway for leptin-induced cytoplasmic lipid body biogenesis and adipose differentiation-related protein accumulation. Furthermore, we demonstrate a previously unrecognized link between intracellular (mTOR) and systemic (leptin) nutrient sensors in macrophage lipid metabolism. Leptin-induced increased formation of cytoplasmic lipid bodies and enhanced inflammatory mediator production in macrophages may have implications for obesity-related cardiovascular diseases.     

The extracellular matrix: an active or passive player in fibrosis?

Fibrosis is characterized by excessive accumulation of collagen and other extracellular matrix (ECM) components, and this process has been likened to aberrant wound healing. The early phases of wound healing involve the formation of a provisional ECM containing fibrin, fibrinogen, and fibronectin. Fibroblasts occupy this matrix and proliferate in response to activators elaborated by leukocytes that have migrated into the wound and are retained by the ECM. This coincides with the appearance of the myofibroblast, a specialized form of fibroblast whose differentiation is primarily driven by cytokines, such as transforming growth factor-β (TGF-β), and by mechanical tension. When these signals are reduced, as when TGF-β secretion is reduced, or as in scar shrinkage, myofibroblasts undergo apoptosis, resulting in a collagen-rich, cell-poor scar. Retention of myofibroblasts in fibrosis has been described as the result of imbalanced cytokine signaling, especially with respect to levels of activated TGF-β. ECM components can regulate myofibroblast persistence directly, since this phenotype is dependent on extracellular hyaluronan, tenascin-C, and the fibronectin splice variant containing the "extra domain A," and also, indirectly, through retention of TGF-β-secreting cells such as eosinophils. Thus the ECM is actively involved in both cellular and extracellular events that lead to fibrosis. Targeting components of the ECM as cells respond to injury and inflammatory stimuli holds promise as a means to avoid development of fibrosis and direct the wound-healing process toward reestablishment of a healthy equilibrium.     

The renal cortical fibroblast in renal tubulointerstitial fibrosis

Renal cortical fibroblasts have key roles in mediating intercellular communication with neighboring/infiltrating cells and extracellular matrix (ECM) and maintenance of renal tissue architecture. They express a variety of cytokines, chemokines, growth factors and cell adhesion molecules, playing an active role in paracrine and autocrine interactions and regulating both fibrogenesis and the interstitial inflammatory response. They additionally have an endocrine function in the production of epoetin. Tubulointerstitial fibrosis, the common pathological consequence of renal injury, is characterized by the accumulation of extracellular matrix largely due to excessive production in parallel with reduced degradation, and activated fibroblasts characterized by a myofibroblastic phenotype. Fibroblasts in the kidney may derive from resident fibroblasts, from the circulating fibroblast population or from haemopoetic progenitor or stromal cells derived from the bone marrow. Cells exhibiting a myofibroblastic phenotype may derive from these sources and from tubular cells undergoing epithelial to mesenchymal transformation in response to renal injury. The number of interstitial myofibroblasts correlates closely with tubulointerstitial fibrosis and progressive renal failure. Hence inhibiting myofibroblast formation may be an effective strategy in attenuating the development of renal failure in kidney disease of diverse etiology.     

Role of TGF-β in chronic kidney disease: an integration of tubular,glomerular and vascular effects

Transforming growth factor beta (TGF-β) has been recognized as an important mediator in the genesis of chronic kidney diseases (CKD), which are characterized by the accumulation of extracellular matrix (ECM) components in the glomeruli (glomerular fibrosis, glomerulosclerosis) and the tubular interstitium (tubulointerstitial fibrosis). Glomerulosclerosis is a major cause of glomerular filtration rate reduction in CKD and all three major glomerular cell types (podocytes or visceral epithelial cells, mesangial cells and endothelial cells) participate in the fibrotic process. TGF-β induces (1) podocytopenia caused by podocyte apoptosis and detachment from the glomerular basement membrane; (2) mesangial expansion caused by mesangial cell hypertrophy, proliferation (and eventually apoptosis) and ECM synthesis; (3) endothelial to mesenchymal transition giving rise to glomerular myofibroblasts, a major source of ECM. TGF-β has been shown to mediate several key tubular pathological events during CKD progression, namely fibroblast proliferation, epithelial to mesenchymal transition, tubular and fibroblast ECM production and epithelial cell death leading to tubular cell deletion and interstitial fibrosis. In this review, we re-examine the mechanisms involved in glomerulosclerosis and tubulointerstitial fibrosis and the way that TGF-β participates in renal fibrosis, renal parenchyma degeneration and loss of function associated with CKD.     

Impaired erythropoietin synthesis in chronic kidney disease is caused by alterations in extracellular matrix composition

Renal fibrosis and anaemia are two of the most relevant events in chronic kidney disease. Fibrosis is characterized by the accumulation of extracellular matrix proteins in the glomeruli and tubular interstitium. Anaemia is the consequence of a decrease in erythropoietin production in fibrotic kidneys. This work analyses the possibility that the accumulation of abnormal collagens in kidney interstitium could be one of the mechanisms responsible for erythropoietin decreased synthesis. In renal interstitial fibroblast grown on collagen I, erythropoietin mRNA expression and HIF‐2α protein decreased, whereas focal adhesion kinase protein (FAK) phosphorylation and proteasome activity increased, compared to cells grown on collagen IV. Proteasome inhibition or FAK inactivation in cells plated on collagen I restored erythropoietin and HIF‐2α expression. FAK inhibition also decreased the collagen I‐dependent proteasome activation. In a model of tubulointerstitial fibrosis induced by unilateral ureteral obstruction in mice, increased collagen I protein content and an almost complete disappearance of erythropoietin mRNA expression were observed in the ureteral ligated kidney with respect to the contralateral control. Interestingly, erythropoietin synthesis was recovered in obstructed mice treated with proteasome inhibitor. These data suggest that reduced kidney erythropoietin synthesis could be caused by the accumulation of abnormal extracellular matrix proteins.     

Duvelisib attenuates bleomycin-induced pulmonary fibrosis via inhibiting the PI3K/Akt/mTOR signalling pathway

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease that seriously threatens the health of patients. The pathogenesis of IPF is still unclear, and there is a lack of effective therapeutic drugs. Myofibroblasts are the main effector cells of IPF, leading to excessive deposition of extracellular matrix (ECM) and promoting the progression of fibrosis. Inhibiting the excessive activation and relieving autophagy blockage of myofibroblasts is the key to treat IPF. PI3K/Akt/mTOR pathway plays a key regulatory role in promoting fibroblast activation and autophagy inhibition in lung fibrosis. Duvelisib is a PI3K inhibitor that can simultaneously inhibit the activities of PI3K-δ and PI3K-γ, and is mainly used for the treatment of relapsed/refractory chronic lymphocytic leukaemia (CLL) and small lymphocytic lymphoma tumour (SLL). In this study, we aimed to examine the effects of Duvelisib on pulmonary fibrosis. We used a mouse model of bleomycin-induced pulmonary fibrosis to evaluate the effects of Duvelisib on pulmonary fibrosis in vivo and further explored the potential pharmacological mechanisms of Duvelisib in lung fibroblasts in vitro. The in vivo experiments showed that Duvelisib significantly alleviated bleomycin-induced collagen deposition and improved pulmonary function. In vitro and in vivo pharmacological experiments showed that Duvelisib dose-dependently suppressed lung fibroblast activation and improved autophagy inhibition by inhibiting the phosphorylation of PI3K, Akt and mTOR. Our results indicate that Duvelisib can alleviate the severity of pulmonary fibrosis and provide potential drugs for the treatment of pulmonary fibrosis.