TGF-β1-activated kinase-1 regulates inflammation and fibrosis in the obstructed kidney

TGF-β Down-regulates Apolipoprotein M Expression through the TAK-1-JNK-c-Jun Pathway in HepG2 Cells

Apolipoprotein M (apoM) is a relatively novel apolipoprotein that plays pivotal roles in many dyslipidemia-associated diseases; however, its regulatory mechanisms are poorly understood. Many cytokines have been identified that down-regulate apoM expression in HepG2 cells, among which transforming growth factor-β (TGF-β) exerts the most potent effects. In addition, c-Jun, a member of the activated protein 1 (AP-1) family whose activity is modulated by c-Jun N-terminal kinase (JNK), decreases apoM expression at the transcriptional level by binding to the regulatory element in the proximal apoM promoter. In this study, we investigated the molecular mechanisms through which TGF-β decreases the apoM level in HepG2 cells. The results revealed that TGF-β inhibited apoM expression at both the mRNA and protein levels in a dose- and time-dependent manner and that it suppressed apoM secretion. These effects were attenuated by treatment of cells with either SP600125 (JNK inhibitor) or c-Jun siRNA. 5Z-7-oxozeaenol [(a TGF-β-activated kinase 1 (TAK-1) inhibitor)] also attenuated the TGF-β-mediated inhibition of apoM expression and suppressed the activation of JNK and c-Jun. These results have demonstrated that TGF-β suppresses apoM expression through the TAK-1-JNK-c-Jun pathway in HepG2 cells.

Structure-guided development of covalent TAK1 inhibitors

TAK1 (transforming growth factor-β-activated kinase 1) is an essential intracellular mediator of cytokine and growth factor signaling and a potential therapeutic target for the treatment of immune diseases and cancer. Herein we report development of a series of 2,4-disubstituted pyrimidine covalent TAK1 inhibitors that target Cys174, a residue immediately adjacent to the 'DFG-motif' of the kinase activation loop. Co-crystal structures of TAK1 with candidate compounds enabled iterative rounds of structure-based design and biological testing to arrive at optimized compounds. Lead compounds such as 2 and 10 showed greater than 10-fold biochemical selectivity for TAK1 over the closely related kinases MEK1 and ERK1 which possess an equivalently positioned cysteine residue. These compounds are smaller, more easily synthesized, and exhibit a different spectrum of kinase selectivity relative to previously reported macrocyclic natural product TAK1 inhibitors such as 5Z-7-oxozeanol.

High glucose induced-macrophage activation through TGF-β-activated kinase 1 signaling pathway

OBJECTIVE AND DESIGN

Transforming growth factor-β-activated kinase 1 (TAK1) plays a pivotal role in innate immune responses and kidney disease, and is critically involved in macrophage activation. However, there is a paucity of data to explore the role of high glucose (HG) in the regulation of TAK1 signaling and its functional role in macrophage activation. We assume that TAK1 signaling in hyperglycemic condition could be a key factor leading to macrophage activation and inflammation response.

METHODS

Mice macrophages were seeded on a 96-well cell culture plate; cell viability was tested after treatment with different concentration of TAK1 inhibitors. Cells were divided into groups (OZ300; MC; NC; HG; HG + OZ30, 100, 300 nM) and treated for given time course. Monocyte chemotactic protein1(MCP-1) and tumor necrosis factor-α (TNF-α) mRNA levels were evaluated by qRT-PCR. Flow cytometry and confocal microscopy are used to analyse the activated macrophage induced by HG. Expression levels of p-TAK1, TAB 1, p-JNK, p-p38MAPK, NF-κBpp65 were detected by western blot. Nuclear translocation of NF-κBp65 was assessed by confocal microscopy.

RESULTS

Our data revealed that high glucose not only significantly increased macrophage activation and subsequently abnormal high-expression of MCP-1 and TNF-α, but likewise remarkably enhanced TAK1 activation, MAPK phosphorylation, NF-κB expression in macrophages. Furthermore, pharmacological inhibition of TAK1 attenuated high glucose-triggered signal pathways, macrophage activation and inflammatory cytokines in a simulated diabetic environment.

CONCLUSION

Our findings suggested that high glucose activated macrophages mainly in TAK1/MAPKs and TAK1/NF-κB-dependent manners, which lead to the polarization of macrophages towards a pro-inflammatory phenotype, and finally lead to diabetic nephropathy. In sum, the study raises novel data about the molecular mechanisms involved in the high glucose-mediated inflammatory response in macrophages.

Areca nut components stimulate ADAM17, IL-1α, PGE2 and 8-isoprostane production in oral keratinocyte: role of reactive oxygen species, EGF and JAK signaling

Betel quid (BQ) chewing is an etiologic factor of oral submucous fibrosis (OSF) and oral cancer. There are 600 million BQ chewers worldwide. The mechanisms for the toxic and inflammatory responses of BQ are unclear. In this study, both areca nut (AN) extract (ANE) and arecoline stimulated epidermal growth factor (EGF) and interleukin-1α (IL-1α) production of gingival keratinocytes (GKs), whereas only ANE can stimulate a disintegrin and metalloproteinase 17 (ADAM17), prostaglandin E2 (PGE2) and 8-isoprostane production. ANE-induced EGF production was inhibited by catalase. Addition of anti-EGF neutralizing antibody attenuated ANE-induced cyclooxygenase-2 (COX-2), mature ADAM9 expression and PGE2 and 8-isoprostane production. ANE-induced IL-1α production was inhibited by catalase, anti-EGF antibody, PD153035 (EGF receptor antagonist) and U0126 (MEK inhibitor) but not by α-naphthoflavone (cytochrome p450-1A1 inhibitor). ANE-induced ADAM17 production was inhibited by pp2 (Src inhibitor), U0126, α-naphthoflavone and aspirin. AG490 (JAK inhibitor) prevented ANE-stimulated ADAM17, IL-1α, PGE2 production, COX-2 expression, ADAM9 maturation, and the ANE-induced decline in keratin 5 and 14, but showed little effect on cdc2 expression and EGF production. Moreover, ANE-induced 8-isoprostane production by GKs was inhibited by catalase, anti-EGF antibody, AG490, pp2, U0126, α-naphthoflavone, Zinc protoporphyrin (ZnPP) and aspirin. These results indicate that AN components may involve in BQ-induced oral cancer by induction of reactive oxygen species, EGF/EGFR, IL-1α, ADAMs, JAK, Src, MEK/ERK, CYP1A1, and COX signaling pathways, and the aberration of cell cycle and differentiation. Various blockers against ROS, EGF, IL-1α, ADAM, JAK, Src, MEK, CYP1A1, and COX can be used for prevention or treatment of BQ chewing-related diseases.

Arecoline-induced pro-fibrotic proteins in LLC-PK1 cells are dependent on c-Jun N-terminal kinase

Areca nut (AN) chewing is associated with chronic kidney disease (CKD). However, the molecular mechanisms of AN-induced CKD are not known. Thus, we studied the effects of arecoline, a major alkaloid of AN, on proximal tubule (LLC-PK1) cells in terms of cytotoxicity, fibrosis, transforming growth factor-β (TGF-β) and c-Jun N-terminal kinase (JNK). We found that arecoline dose (0.1-0.5mM) and time (24-72h)-dependently induced cytotoxicity without causing cell death. Arecoline (0.25 mM) also time-dependently (24-72h) increased fibronectin and plasminogen activator inhibitor-1 (PAI1) protein expressions. Arecoline (0.25 mM) time-dependently (24-72h) increased TGF-β gene transcriptional activity and supernatant levels of active TGF-β1. Moreover, arecoline (0.25 mM) activated JNK while SP600125 (a JNK inhibitor) attenuated arecoline-induced TGF-β gene transcriptional activity. SP600125, but not SB431542 (a TGF-β receptor type I kinase inhibitor), attenuated arecoline-induced fibronectin and PAI1 protein expressions. Finally, tubulointerstitial fibrosis occurred and renal cortical expressions of fibronectin and PAI1 proteins increased in arecoline-fed mice at 24 weeks. We concluded that arecoline induced tubulointerstitial fibrosis in mice while arecoline-induced TGF-β and pro-fibrotic proteins (fibronectin, PAI1) are dependent on JNK in LLC-PK1 cells.

A role for spleen tyrosine kinase in renal fibrosis in the mouse obstructed kidney

AIMS

Spleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase involved in the signalling pathways of the B cell receptor, Fcγ-receptor and some leukocyte integrins. However, Syk can also be expressed by some non-haematopoietic cell types, although whether Syk signalling in these cells contributes to the pathogenesis of kidney disease is unknown. To address this question, we examined the function of Syk in antibody-independent renal interstitial fibrosis in the unilateral ureteric obstruction (UUO) model.

MAIN METHODS

Groups of C57BL/6J mice were treated with a selective Syk inhibitor (CC0417, 30 mg/kg/bid), vehicle, or no treatment, from the time of surgery until being killed 7 days later.

KEY FINDINGS

A substantial accumulation of interstitial Syk(+) cells was seen in the UUO kidney. Double staining identified Syk expression by infiltrating macrophages and by a subset of α-SMA(+) myofibroblasts. CC0417 treatment substantially reduced the Syk(+) cell population in conjunction with a reduction in both myofibroblast and macrophage accumulation. This was associated with a substantial reduction in collagen IV deposition and mRNA levels of pro-fibrotic (collagen I, collagen IV, fibronectin, α-SMA, TGF-β1 and PAI-1) and pro-inflammatory molecules (MCP-1, TNF-α and NOS2). CC0417 treatment reduced both PDGF-B mRNA levels and Ki67(+) proliferating interstitial cells in the UUO kidney. Furthermore, CC0417 inhibited PDGF-AB induced ERK activation and cell proliferation of cultured primary kidney fibroblasts.

SIGNIFICANCE

This study has identified a pathologic role for Syk in renal interstitial fibrosis. Syk inhibitors may have therapeutic potential in chronic fibrotic kidney disease.

TGF-β signaling in the kidney: profibrotic and protective effects

Transforming growth factor-β (TGF-β) is generally considered as a central mediator of fibrotic diseases. Indeed, much focus has been placed on inhibiting TGF-β and its downstream targets as ideal therapeutic strategies. However, pharmacological blockade of TGF-β has not yet translated into successful therapy for humans, which may be due to pleiotropic effects of TGF-β signaling. Equally, TGF-β signaling as a protective response in kidney injury has been relatively underexplored. An emerging body of evidence from experimental kidney disease models indicates multifunctionality of TGF-β capable of inducing profibrotic and protective effects. This review discusses recent advances highlighting the diverse roles of TGF-β in promoting not only renal fibrosis but also protective responses of TGF-β signaling. We review, in particular, growing evidence that supports protective effects of TGF-β by mechanisms which include inhibiting inflammation and induction of autophagy. Additional detailed studies are required to fully understand the diverse mechanisms of TGF-β actions in renal fibrosis and inflammation that will likely direct toward effective antifibrotic therapies.

Blockade of TGF-β-activated kinase 1 prevents advanced glycation end products-induced inflammatory response in macrophages

Advanced glycation end products (AGEs), inflammatory-activated macrophages are essential in the initiation and progression of diabetic nephropathy (DN). TGF-β-activated kinase 1 (TAK1) plays a vital role in innate immune responses and inflammation. However, little information has been available about the effects of AGEs on the regulation of TAK1 expression and underlying mechanisms in AGEs-stimulated macrophage activation. We hypothesized TAK1 signal pathway in AGEs conditions could be a vital factor contributing to macrophage activation and inflammation. Thus, in the present study, we used bone marrow-derived macrophages (BMMs) to explore the functional role and potential mechanisms of TAK1 pathway under AGEs conditions. Results indicated that TAK1 played important roles in AGEs-induced mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B protein (NF-κB) activation, which regulated the production of monocyte chemo-attractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) in AGEs-stimulated macrophages. The results also suggested that TAK1 inhibitor (5Z-7-oxozeaenol) could inhibit AGEs-induced macrophage activation to down-regulate inflammatory cytokine production via MAPKs and NF-κB pathways, indicating that 5Z-7-oxozeaenol might be an immunoregulatory agent against AGEs-stimulated inflammatory response in DN.

Targeting of TGF-β-activated protein kinase 1 inhibits chemokine (C-C motif) receptor 7 expression, tumor growth and metastasis in breast cancer

TGF-β-activated protein kinase 1 (TAK1) is a critical mediator in inflammation, immune response and cancer development. Our previous study demonstrated that activation of TAK1 increases the expression of chemokine (C-C motif) receptor 7 (CCR7) and promotes lymphatic invasion ability of breast cancer cells. However, the expression and association of activated TAK1 and CCR7 in breast tumor tissues is unknown and the therapeutic effect by targeting TAK1 is also unclear. We showed that activated TAK1 (as indicated by phospho-TAK1) and its binding protein TAB1 are strongly expressed in breast tumor tissues (77% and 74% respectively). In addition, increase of phospho-TAK1 or TAB1 is strongly associated with over-expression of CCR7. TAK1 inhibitor 5Z-7-Oxozeaenol (5Z-O) inhibited TAK1 activity, suppressed downstream signaling pathways including p38, IκB kinase (IKK) and c-Jun N-terminal kinase (JNK) and reduced CCR7 expression in metastatic MDA-MB-231 cells. In addition, 5Z-O repressed NF-κB- and c-JUN-mediated transcription of CCR7 gene. Knockdown of TAB1 attenuated CCR7 expression and tumor growth in an orthotopic animal study. More importantly, lymphatic invasion and lung metastasis were suppressed. Collectively, our results demonstrate that constitutive activation of TAK1 is frequently found in human breast cancer and this kinase is a potential therapeutic target for this cancer.

Mycophenolic acid inhibits the phosphorylation of nuclear factor‑κB and Akt in renal tubular epithelial cells

Renal tubulointerstitial injury induced by albumin overload is a critical stage during the progression of renal interstitial fibrosis and progression of chronic renal diseases. Inosine‑5'‑monophosphate dehydrogenase inhibitor mycophenolate mofetil (MMF), a pro‑drug of mycophenolic acid (MPA), is known to attenuate the progression of renal interstitial fibrosis; however, the underlying molecular mechanisms of the anti‑fibrotic effects of derivatives of MMF have not yet been studied. The present study assessed the effects of the MPA on renal tubular epithelial cells. Transforming growth factor beta 1 (TGF‑β1) has been indicated to have a central role in the underlying molecular mechanisms of renal fibrosis; furthermore, nuclear transcription factor‑κB (NF‑κB) is a transcription factor associated with the production of inflammatory cytokines, cell proliferation and apoptosis. In addition, the Akt signaling pathway has important roles in cell proliferation, differentiation, metabolism and apoptosis. The present study subjected the NRK52E rat kidney epithelial‑derived cell line to albumin overload, which resulted in an increase in TGF‑β1 production as well as phosphorylation of Akt and the binding activity of NF‑κB to the promoter region of the TGF‑β1 gene, which was, however, reduced following pre‑incubation of the cells with MPA. In addition, the effects of albumin were partially blocked by Ly294002, a specific inhibitor of Akt. In conclusion, the results of the present study suggested that MPA may exert its anti‑fibrotic effects by inhibiting the upregulation of TGF‑β1 and the activation of NF‑κB following albumin overload, which may be partly dependent on the Akt pathway.

ASK1 Inhibitor Halts Progression of Diabetic Nephropathy in Nos3-Deficient Mice

p38 mitogen-activated protein kinase (MAPK) signaling promotes diabetic kidney injury. Apoptosis signal-regulating kinase (ASK)1 is one of the upstream kinases in the p38 MAPK-signaling pathway, which is activated by inflammation and oxidative stress, suggesting a possible role for ASK1 in diabetic nephropathy. In this study, we examined whether a selective ASK1 inhibitor can prevent the induction and progression of diabetic nephropathy in mice. Diabetes was induced in hypertensive endothelial nitric oxide synthase (Nos3)-deficient mice by five low-dose streptozotocin (STZ) injections. Groups of diabetic Nos3(-/-) mice received ASK1 inhibitor (GS-444217 delivered in chow) as an early intervention (2-8 weeks after STZ) or late intervention (weeks 8-15 after STZ). Control diabetic and nondiabetic Nos3(-/-) mice received normal chow. Treatment with GS-444217 abrogated p38 MAPK activation in diabetic kidneys but had no effect upon hypertension in Nos3(-/-) mice. Early intervention with GS-444217 significantly inhibited diabetic glomerulosclerosis and reduced renal dysfunction but had no effect on the development of albuminuria. Late intervention with GS-444217 improved renal function and halted the progression of glomerulosclerosis, renal inflammation, and tubular injury despite having no effect on established albuminuria. In conclusion, this study identifies ASK1 as a new therapeutic target in diabetic nephropathy to reduce renal inflammation and fibrosis independent of blood pressure control.

Impact of AMP-Activated Protein Kinase α1 Deficiency on Tissue Injury following Unilateral Ureteral Obstruction

Background

AMP-activated protein kinase (Ampk) is a sensor of the cellular energy status and a powerful regulator of metabolism. Activation of Ampk was previously shown to participate in monocyte-to-fibroblast transition and matrix protein production in renal tissue. Thus, the present study explored whether the catalytic Ampkα1 isoform participates in the regulation of the renal fibrotic response following unilateral ureteral obstruction (UUO).

Methods

UUO was induced in gene-targeted mice lacking functional Ampkα1 (Ampkα1^-/-) and in corresponding wild-type mice (Ampkα1^+/+). In the obstructed kidney and, for comparison, in the non-obstructed control kidney, quantitative RT-PCR, Western blotting and immunostaining were employed to determine transcript levels and protein abundance, respectively.

Results

In Ampkα1^+/+ mice, UUO significantly up-regulated the protein abundance of the Ampkα1 isoform, but significantly down-regulated the Ampkα2 isoform in renal tissue. Phosphorylated Ampkα protein levels were significantly increased in obstructed kidney tissue of Ampkα1^+/+ mice but not of Ampkα1^-/- mice. Renal expression of α-smooth muscle actin was increased following UUO, an effect again less pronounced in Ampkα1^-/- mice than in Ampkα1^+/+ mice. Histological analysis did not reveal a profound effect of Ampkα1 deficiency on collagen 1 protein deposition. UUO significantly increased phosphorylated and total Tgf-ß-activated kinase 1 (Tak1) protein, as well as transcript levels of Tak1-downstream targets c-Fos, Il6, Pai1 and Snai1 in Ampkα1^+/+ mice, effects again significantly ameliorated in Ampkα1^-/- mice. Moreover, Ampkα1 deficiency inhibited the UUO-induced mRNA expression of Cd206, a marker of M2 macrophages and of Cxcl16, a pro-fibrotic chemokine associated with myeloid fibroblast formation. The effects of Ampkα1 deficiency during UUO were, however, paralleled by increased tubular injury and apoptosis.

Conclusions

Renal obstruction induces an isoform shift from Ampkα2 towards Ampkα1, which contributes to the signaling involved in cell survival and fibrosis.

Transforming growth factor-β-activated kinase 1 resistance limits glucocorticoid responsiveness to Toll-like receptor 4-mediated inflammation

Glucocorticoids (GC) are among the most effective anti-inflammatory drugs, but are often associated with serious adverse effects or inadequate therapeutic responses. Here, we use activation of different Toll-like receptors (TLRs) by their respective ligands to evaluate context-specific GC sensitivity in the macrophage. Recruitment and activation of transforming growth factor-β-activated kinase 1 (TAK1), downstream of TLR engagement, is crucial in activating multiple inflammatory pathways, and contributes to inflammatory disorders. We hypothesize that GC exert anti-inflammatory effects through regulation of TAK1. Both in vivo and in vitro, in comparison to other TLRs, there was limited GC potency in restricting TLR4 ligand-mediated secretion of interleukin-6, tumour necrosis factor-α and interleukin-12. Also, we found that inactivation of TAK1 both in vivo and in vitro strongly inhibits TLR4-induced inflammation-associated genes beyond the suppressive effects from GC treatment. However, there was no effect of TAK1 inactivation on GC inhibition of TLR3- or TLR9-initiated inflammatory actions. Together, our findings demonstrate that GC resistance for TAK1 activation associated with TLR4 engagement may be an important contributor to GC resistance in inflammatory disorders.

TGF-β1 induced transdifferentiation of rpe cells is mediated by TAK1

BACKGROUND AND AIM

Proliferative vitreoretinopathy (PVR) is an active process that develops as a complication upon retinal detachment (RD), accompanied by formation of fibrotic tissue. The main cells involved in the development of fibrotic tissue during PVR are the retinal pigment epithelial (RPE) cells. The RPE cells undergo epithelial-mesenchymal transition (EMT) which leads to complex retinal detachment and loss of vision. Transforming growth factor-β1 (TGF-β1) is considered as the main player in the EMT of RPE cells, even though the mechanism is not fully understood. This study was performed to determine the possible involvement of transforming growth factor β activated kinase 1 (TAK1) in the EMT process of the RPE cells.

METHODOLOGY

ARPE-19 Cells were treated with 5Z-7 oxozeaenol (TAK1 inhibitor) or SB431542 (TGF-β1 receptor kinase inhibitor) followed by TGF-β1 stimulation. Immunofluorescence, scratch assay Real time PCR and collagen contraction assay assessed the EMT features. The phosphorylation of Smad2/3 and p38 was examined using western blots analysis.

RESULTS

This study demonstrates that stimulation of RPE cells with TGF-β1 increases α-SMA expression, cell migration and cell contractility, all of which are EMT features. Remarkably, addition of TAK1 inhibitor abolishes all these processes. Furthermore, we show hereby that TAK1 regulates not only the activation of the non-canonical cascade of TGF-β1 (p38), but also the canonical cascade, the Smad2/3 activation. Thus, the outcome of the TGF-β response in RPE cells is TAK1 dependent.

CONCLUSIONS/SIGNIFICANCE

This work demonstrated TAK1, a component of the non-canonical pathway of TGF-β1, is a key player in the EMT process, thus provides deep insight into the pathogenesis of PVR. The ability to halt the process of EMT in RPE cells may reduce the severity of the fibrotic response that occurs upon PVR, leading to a better prognosis and increase the probability of success in RD treatment.

Ginsenoside-Rg1 inhibits endoplasmic reticulum stress-induced apoptosis after unilateral ureteral obstruction in rats

AIM

Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are implicated in many fibrotic diseases, including renal fibrosis. Whether Ginsenoside-Rg1 (G-Rg1) could attenuate renal fibrosis via suppression of ER stress and UPR has not been reported. The aim of this study was to explore the effect of G-Rg1 on ER stress and UPR-induced apoptosis in kidneys with unilateral ureteral obstruction (UUO) rat model.

METHODS

Twenty-four male Sprague-Dawley rats were randomly divided into control group, model group and G-Rg1 treatment group. G-Rg1 was administered to rats by intraperitoneal injection. Renal interstitial fibrosis in the model group was developed by UUO in rats. Renal function was estimated by the levels of serum creatinine (Scr) and blood urea nitrogen (BUN). Renal pathological damage was evaluated by hematoxylin and eosin (HE) and Masson's trichrome staining. The ER stress was assessed with glucose-regulated protein (GRP) 78 expression, and the proapoptotic response was detected with CCAAT/enhancer-binding protein homologous protein (CHOP) and caspase-12 expressions by Western Blot. The number of apoptotic cells was determined by Terminal-deoxynucleotidyl Transferase Mediated Nick End Labeling (TUNEL) analysis.

RESULTS

UUO for 14 days aggravated renal function, renal damage and renal interstitial fibrosis, activated ER stress response (induction of GRP78 protein), enhanced the proapoptotic response (increase in CHOP and caspase-12 proteins) and increased the number of apoptotic cells (shown by the TUNEL assay). Treatment with G-Rg1 significantly ameliorates the renal pathological lesions and decreases expressions of ER stress-associated proteins and the level of apoptotic cells in kidneys.

CONCLUSION

G-Rg1 suppresses renal cell apoptotic and fibrotic process partly through inhibition of ERS- and UPR-related apoptotic pathway in the kidneys after UUO.

Genistein alleviates pressure overload-induced cardiac dysfunction and interstitial fibrosis in mice

BACKGROUND AND PURPOSE

Pressure overload-induced cardiac interstitial fibrosis is viewed as a major cause of heart failure in patients with hypertension or aorta atherosclerosis. The purpose of this study was to investigate the effects and the underlying mechanisms of genistein, a natural phytoestrogen found in soy bean extract, on pressure overload-induced cardiac fibrosis.

EXPERIMENTAL APPROACH

Genisten was administered to mice with pressure overload induced by transverse aortic constriction. Eight weeks later, its effects on cardiac dysfunction, hypertrophy and fibrosis were determined. Its effects on proliferation, collagen production and myofibroblast transformation of cardiac fibroblasts (CFs) and the signalling pathways were also assessed in vitro.

KEY RESULTS

Pressure overload-induced cardiac dysfunction, hypertrophy and fibrosis were markedly attenuated by genistein. In cultured CFs, genistein inhibited TGFβ1-induced proliferation, collagen production and myofibroblast transformation. Genistein suppressed TGFβ-activated kinase 1 (TAK1) expression and produced anti-fibrotic effects by blocking the TAK1/MKK4/JNK pathway. Further analysis indicated that it up-regulated oestrogen-dependent expression of metastasis-associated gene 3 (MTA3), which was found to be a negative regulator of TAK1. Silencing MTA3 by siRNA, or inhibiting the activity of the MTA3-NuRD complex with trichostatin A, abolished genistein's anti-fibrotic effects.

CONCLUSIONS AND IMPLICATIONS

Genistein improved cardiac function and inhibited cardiac fibrosis in response to pressure overload. The underlying mechanism may involve regulation of the MTA3/TAK1/MKK4/JNK signalling pathway. Genistein may have potential as a novel agent for prevention and therapy of cardiac disorders associated with fibrosis.

ASK1/p38 signaling in renal tubular epithelial cells promotes renal fibrosis in the mouse obstructed kidney

Stress-activated kinases p38 MAPK and JNK promote renal fibrosis; however, how the pathways by which these kinases are activated in kidney disease remain poorly defined. Apoptosis signal-regulating kinase 1 (ASK1/MAPKKK5) is a member of the MAPKKK family that can induce activation of p38 and JNK. The present study examined whether ASK1 induces p38/JNK activation and renal fibrosis in unilateral ureteric obstruction (UUO) using wild-type (WT) and Ask1-deficient ( Ask1−/−) mice. Basal p38 and JNK activation in WT kidneys was increased three- to fivefold in day 7 UUO mice in association with renal fibrosis. In contrast, there was no increase in p38 activation in Ask1−/− UUO mice, whereas JNK activation was only partially increased. The progressive increase in kidney collagen (hydroxyproline) content seen on days 7 and 12 of UUO in WT mice was significantly reduced in Ask1−/− UUO mice in association with reduced α-smooth muscle actin-positive myofibroblast accumulation. However, cultured WT and Ask1−/− renal fibroblasts showed equivalent proliferation and matrix production, indicating that ASK1 acts indirectly on fibroblasts. Tubular epithelial cells are the main site of p38 activation in the obstructed kidney. Angiotensin II and H2O2, but not IL-1 or lipopolysaccharide, induced p38 activation and upregulation of transforming growth factor-β1, platelet-derived growth factor-B, and monocyte chemoattractant protein-1 production was suppressed in Ask1−/− tubular epithelial cells. In addition, macrophage accumulation was significantly inhibited in Ask1−/− UUO mice. In conclusion, ASK1 is an important upstream activator of p38 and JNK signaling in the obstructed kidney, and ASK1 is a potential therapeutic target in renal fibrosis.

Astragaloside IV ameliorates renal fibrosis via the inhibition of mitogen-activated protein kinases and antiapoptosis in vivo and in vitro

Apoptosis of renal tubular cells plays a crucial role in renal fibrosis. Astragaloside IV (AS-IV), a compound extracted from Radix Astragali, has been shown to inhibit renal tubular cell apoptosis induced by high glucose, but its role in preventing chronic renal fibrosis as well as the underlying molecular mechanisms involved still remain obscure. In this study, human kidney tubular epithelial cells induced by transforming growth factor-β1 (TGF-β1) were used to investigate the protective role of AS-IV in antifibrosis. As an in vivo model, mice subjected to unilateral ureteral obstruction (UUO) were administered AS-IV (20 mg/kg) by intraperitoneal injection for 7 days. AS-IV significantly alleviated renal mass loss and reduced the expression of α-smooth muscle actin, fibronectin, and collagen IV both in vitro and in vivo, suggesting that this compound functions in the inhibition of renal tubulointerstitial fibrosis. Furthermore, transferase-mediated dUTP nick-end labeling assay results both in vivo and in vitro showed that AS-IV significantly attenuated both UUO and TGF-β1-induced cell apoptosis and prevented renal tubular epithelial cell injury in a dose-dependent manner. Western blotting results also revealed that the antiapoptotic effect of AS-IV was reflected in the inhibition of caspase-3 activation, which might be mediated primarily by the downregulation of mitogen-activated protein kinase effectors phospho-p38 and phospho-c-Jun N-terminal kinase. These data infer that AS-IV effectively attenuates the progression of renal fibrosis after UUO injury and may have a promising clinical role as a potential antifibrosis treatment in patients with chronic kidney disease.

Berberine hydrochloride prevents postsurgery intestinal adhesion and inflammation in rats

Intestinal adhesion, characterized by connection of the loops of the intestine with other abdominal organs by fibrous tissue bands, remains an inevitable event of abdominal operations and can cause a number of complications. Berberine hydrochloride (berberine), a natural plant alkaloid derived from Chinese herbal medicine, is characterized by diverse pharmacological effects, such as anticancer and lower elevated blood glucose. This study is designed to investigate the effects of berberine on adhesion and inflammation after abdominal surgeries and the underlying molecular mechanisms. Adhesion severity grades and collagen deposition were assessed 14 days after surgery. We evaluated the levels of intercellular adhesion molecule-1 (ICAM-1) and inflammatory cytokines interleukin-1β (IL-1β), IL-6, transforming growth factor β (TGF-β), tumor necrosis factor-α (TNF-α), and examined transforming growth factor-activated kinase 1 (TAK1)/c-Jun N-terminal kinase (JNK) and TAK1/nuclear factor κB (NF-κB) signaling. The surgery group experienced the most severe adhesions, and berberine strikingly reduced the density and severity of adhesion. Results showed significant lower expression of IL-1β, IL-6, TGF-β, TNF-α, and ICAM-1, in berberine groups compared with the operation group. Activities of phosphorylated JNK and phosphorylated NF-κB were inhibited in the berberine groups compared with the surgery group. Our novel findings identified berberine hydrochloride as a promising strategy to prevent adhesion by downregulating ICAM-1 and reduce inflammation by inhibiting the TAK1/JNK and TAK1/NF-κB signaling after abdominal surgery, which brought out a good therapeutic approach for the development of clinical application for postoperative abdominal adhesion and inflammation.

Histopathological changes in supraspinous ligaments, ligamentum flava and paraspinal muscle tissues of patients with ankylosing spondylitis

OBJECTIVE

To examine the histopathological changes in spinal tissues of ankylosing spondylitis (AS) patients.

METHODS

Tissue samples from 10 AS patients and 10 control subjects were obtained. Hematoxylin and eosin, picrosirius, Masson and van Gieson stainings were utilized to determine the pathological changes in tissues. Ultrastructural alterations were examined by electronic microscopy. Proteoglycan levels were assessed by enzyme-linked immunosorbent assays (ELISA). Matrix metalloproteinase-3 (MMP-3), transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α) levels were evaluated by immunohistochemistry.

RESULTS

Our results demonstrate that the density of collagen fibrils was reduced in the supraspinous ligaments of AS tissue and fibrils were loosely and irregularly organized as compared to a regular distribution of collagen fibrils in controls. In ligamentum flava from AS patients, activated fibroblasts with enlarged nuclei were detected, while the number of elastic fibers was greatly decreased. Paraspinal muscle tissues of AS patients exhibited increased collagen fibril accumulation and atrophy. Significantly decreased proteoglycan and elevated MMP-3 levels were found in supraspinous ligament samples from AS patients (P < 0.01). Additionally, the levels of TGF-β1 in ligamentum flava and paraspinal muscle tissues of AS patients were increased (P < 0.01). The expression of TNF-α was also upregulated in the ligamentum flavum (P < 0.01), with no significant difference in the paraspinal muscle between control and AS patients (P > 0.05).

CONCLUSIONS

Our findings reveal histopathological changes that occur in certain spinal tissues of AS patients and suggest that increased levels of MMP-3 and TGF-β1 may contribute to the pathogenesis of AS.

Endothelial dysfunction exacerbates renal interstitial fibrosis through enhancing fibroblast Smad3 linker phosphorylation in the mouse obstructed kidney

Endothelial dysfunction and enhanced transforming growth factor-β (TGF-β)/Smad3 signalling are common features of progressive renal fibrosis. This study investigated a potential link between these mechanisms. In unilateral ureteric obstruction (UUO) we observed an acute (6 hr) down-regulation of nitric oxide synthase 3 (NOS3/eNOS) levels and increased phosphorylation of the linker region of Smad3 at T179 and S208 in Smad3/JNK complexes. These events preceded Smad3 C-terminal domain phosphorylation and the induction of myofibroblast proliferation at 48 hrs. Mice deficient in NOS3 showed enhanced myofibroblast proliferation and collagen accumulation compared to wild type mice in a 7 day UUO model. This was associated with enhanced phosphorylation of Smad3 T179 and S208 by 92% and 88%, respectively, whereas Smad3-C-terminal phosphorylation was not affected. Resolvin D1 (RvD1) can suppress renal fibrosis in the UUO model, and further analysis herein showed that RvD1 protected against endothelial dysfunction and suppressed Smad3/JNK complex formation with a consequent reduction in phosphorylation of Smad3 T179 and S208 by 78% and 65%, respectively, while Smad3 C-terminal phosphorylation was unaltered. In vitro, conditioned media from mouse microvascular endothelial cells (MMEC) treated with a general inhibitor of nitric oxide synthase (L-NAME) augmented the proliferation and collagen production of renal fibroblasts (NRK49F cells) compared to control MMEC media and this was associated with increased phosphorylation of JNK and Smad3 T179 and S208, whereas Smad3-C-terminal domain phosphorylation was unaffected. The addition of RvD1 to L-NAME treated MMEC abrogated these effects of the conditioned media on renal fibroblasts. Finally, Smad3 T179/V and S208/A mutations significantly inhibit TGF-β1 induced up-regulation collagen I promoter. In conclusion, these data suggest that endothelial dysfunction can exacerbate renal interstitial fibrosis through increased fibroblast proliferation and collagen production via enhanced Smad3 linker phosphorylation.

Signalling mechanisms involved in renal pathological changes during cisplatin-induced nephropathy

CONTEXT

Cisplatin, a coordination platinum complex, is used as a potential anti-neoplastic agent, having well recognized DNA-damaging property that triggers cell-cycle arrest and cell death in cancer therapy. Beneficial chemotherapeutic actions of cisplatin can be detrimental for kidneys.

BACKGROUND

Unbound cisplatin gets accumulated in renal tubular cells, leading to cell injury and death. This liable action of cisplatin on kidneys is mediated by altered intracellular signalling pathways such as mitogen-activated protein kinase (MAPK), extracellular regulated kinase (ERK), or C- Jun N terminal kinase/stress-activated protein kinase (JNK/SAPK). Further, these signalling alterations are responsible for release and activation of tumour necrosis factor (TNF-α), mitochondrial dysfunction, and apoptosis, which ultimately cause the renal pathogenic process. Cisplatin itself enhances the generation of reactive oxygen species (ROS) and activation of nuclear factor-κB (NF-κB), inflammation, and mitochondrial dysfunction, which further leads to renal apoptosis. Cisplatin-induced nephropathy is also mediated through the p53 and protein kinase-Cδ (PKCδ) signalling pathways.

OBJECTIVE

This review explores these signalling alterations and their possible role in the pathogenesis of cisplatin-induced renal injury.

Inhibition of transforming growth factor beta-activated kinase 1 confers neuroprotection after traumatic brain injury in rats

The transforming growth factor beta-activated kinase 1 (TAK1), a member of the Mitogen-activated protein kinase kinase kinase family, is characterized as a key regulator in inflammatory and apoptosis signaling pathways. The aim of the present study was to evaluate the role of the TAK1 pathway in experimental traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were subjected to TBI using a modified Feeney's weight-drop model. The time course showed that a significant increase of TAK1 and p-TAK1 expression in the cortex after TBI. Moreover, TBI induced TAK1 redistribution both in neurons and astrocytes of the lesion boundary zone. The effects of specific inhibition of the TAK1 pathway by 5Z-7-oxozeaenol (OZ, intracerebroventricular injection at 10min post-trauma) on histopathological and behavioral outcomes in rats were assessed at 24h post injury. The number of TUNEL-positive stained cells was diminished and neuronal survival and neurological function were improved with OZ treatment. Biochemically, the high dose of OZ significantly reduced the levels of TAK1 and p-TAK1, further decreased nuclear factor-κB and activator protein 1 activities and the release of inflammatory cytokines. In addition, we found that both 10min and 3h post-trauma OZ therapies could markedly improve neurological function and neuronal survival after long-term survival. These results revealed that the TAK1 pathway is activated after experimental TBI and the inhibitor OZ affords significant neuro- protection and amelioration of neurobehavioral deficits after experimental TBI, suggesting a potential rationale for manipulating this pathway in clinical practice.

TAK1 is required for dermal wound healing and homeostasis

Dermal connective tissue is a supportive structure required for skin's barrier function; dysregulated dermal homeostasis results in chronic wounds and fibrotic diseases. The multifunctional cytokine transforming growth factor (TGF) β promotes connective tissue deposition, repair, and fibrosis. TGF-β acts through well-defined canonical pathways; however, the non-canonical pathways through which TGF-β selectively promotes connective tissue deposition are unclear. In dermal fibroblasts, we show that inhibition of the non-canonical TGF-β-activated kinase 1 (TAK1) selectively reduced the ability of TGF-β to induce expression of a cohort of wound healing genes, such as collagens, CCN2, TGF-β1, and IL-6. Fibroblast-specific TAK1-knockout mice showed impaired cutaneous tissue repair and decreased collagen deposition, α-smooth muscle actin and CCN2 expression, proliferating cell nuclear antigen staining, and c-Jun N-terminal kinase and p38, but not Smad3, phosphorylation. TAK1-deficient fibroblasts showed reduced cell proliferation, migration, cell attachment/spreading, and contraction of a floating collagen gel matrix. TAK1-deficient mice also showed progressively reduced skin thickness and collagen deposition. Thus, TAK1 is essential for connective tissue deposition in the dermis.

Transforming growth factor-β1 receptor inhibition preserves glomerulotubular integrity during ureteral obstruction in adults but worsens injury in neonatal mice

Unilateral ureteral obstruction (UUO), a widely used model of chronic kidney disease and congenital obstructive uropathy, causes proximal tubular injury and formation of atubular glomeruli. Because transforming growth factor-β1 (TGF-β1) is a central regulator of renal injury, neonatal and adult mice were subjected to complete UUO while under general anesthesia and treated with vehicle or ALK5 TGF-β1 receptor inhibitor (IN-1130, 30 mg·kg(-1)·day(-1)). After 14 days, glomerulotubular integrity and proximal tubular mass were determined by morphometry of Lotus tetragonolobus lectin distribution, and the fraction of atubular glomeruli was determined by serial section analysis of randomly selected individual glomeruli. Glomerular area, macrophage infiltration, fibronectin distribution, and interstitial collagen were measured by morphometry. Compared with placebo, inhibition of TGF-β1 by IN-1130 decreased apoptosis and formation of atubular glomeruli, prevented parenchymal loss, increased glomerular area and glomerulotubular integrity, and increased proximal tubule fraction of the adult obstructed kidney parenchyma from 17 to 30% (P < 0.05, respectively). IN-1130 decreased macrophage infiltration and fibronectin and collagen deposition in the adult obstructed kidney by ∼50% (P < 0.05, respectively). In contrast to these salutary effects in the adult, IN-1130 caused widespread necrosis in obstructed neonatal kidneys. We conclude that whereas IN-1130 reduces obstructive injury in adult kidneys through preservation of glomerulotubular integrity and proximal tubular mass, TGF-β1 inhibition aggravates obstructive injury in neonates. These results indicate that while caution is necessary in treating congenital uropathies, ALK5 inhibitors may prevent nephron loss due to adult kidney disease.

TGF-β signaling via TAK1 pathway: role in kidney fibrosis

In progressive kidney diseases, fibrosis represents the common pathway to end-stage kidney failure. Transforming growth factor-β1 (TGF-β1) is a pleiotropic cytokine that has been established as a central mediator of kidney fibrosis. Emerging evidence shows a complex scheme of signaling networks that enable multifunctionality of TGF-β1 actions. Specific targeting of the TGF-β signaling pathway is seemingly critical and an attractive molecular therapeutic strategy. TGF-β1 signals through the interaction of type I and type II receptors to activate distinct intracellular pathways involving the Smad and the non-Smad. The Smad signaling axis is known as the canonical pathway induced by TGF-β1. Importantly, recent investigations have shown that TGF-β1 also induces various non-Smad signaling pathways. In this review, we focus on current insights into the mechanism and function of the Smad-independent signaling pathway via TGF-β-activated kinase 1 and its role in mediating the profibrotic effects of TGF-β1.

Cardiomyocyte ATP release through pannexin 1 aids in early fibroblast activation

Fibrosis following myocardial infarction is associated with increases in arrhythmias and sudden cardiac death. Initial steps in the development of fibrosis are not clear; however, it is likely that cardiac fibroblasts play an important role. In immune cells, ATP release from pannexin 1 (Panx1) channels acts as a paracrine signal initiating activation of innate immunity. ATP has been shown in noncardiac systems to initiate fibroblast activation. Therefore, we propose that ATP release through Panx1 channels and subsequent fibroblast activation in the heart drives the development of fibrosis in the heart following myocardial infarction. We identified for the first time that Panx1 is localized within sarcolemmal membranes of canine cardiac myocytes where it directly interacts with the postsynaptic density 95/Drosophila disk large/zonula occludens-1-containing scaffolding protein synapse-associated protein 97 via its carboxyl terminal domain (amino acids 300-357). Induced ischemia rapidly increased glycosylation of Panx1, resulting in increased trafficking to the plasma membrane as well as increased interaction with synapse-associated protein 97. Cellular stress enhanced ATP release from myocyte Panx1 channels, which, in turn, causes fibroblast transformation to the activated myofibroblast phenotype via activation of the MAPK and p53 pathways, both of which are involved in the development of cardiac fibrosis. ATP release through Panx1 channels in cardiac myocytes during ischemia may be an early paracrine event leading to profibrotic responses to ischemic cardiac injury.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.

Targeting of TAK1 in inflammatory disorders and cancer

The transcription factors nuclear factor-κB (NF-κB) and activating protein-1 (AP-1) are critical regulators of stress responses, immunity, inflammation and cancer. A large variety of cellular stimuli utilize these signaling pathways through a common upstream kinase transforming growth factor-β-activated kinase 1 (TAK1). TAK1 was originally identified as a mitogen-activated kinase kinase kinase (MAP3K) activated by transforming growth factor-β (TGF-β); however, it has been characterized as a key regulator in inflammatory and immune signaling pathways. In addition, microbial proteins and components of host cell signaling scramble for the TAK1 complex in innate immunity. This review highlights the recent advances in the activation mechanisms and physiological functions of TAK1. Research targeting TAK1 raises the potential for new therapeutic options for inflammatory disorders, including cancer.

Less expression of prohibitin is associated with increased caspase-3 expression and cell apoptosis in renal interstitial fibrosis rats

AIMS

Prohibitin (PHB), a ubiquitous protein, is involved in a variety of molecular functions. Renal interstitial fibrosis (RIF) is a hallmark of common progressive chronic diseases that lead to renal failure. This study was performed to investigate whether PHB was associated with caspase-3 expression/cell apoptosis in RIF rats.

METHODS

Twenty-four male Wistar rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 12, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14 days and 28 days after surgery. RIF index, cell apoptosis index, protein expression of PHB, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV), fibronectin (FN) or caspase-3 in renal interstitium, and mRNA expression of PHB in renal tissue were detected.

RESULTS

Compared with that in the SHO group, the PHB expression (mRNA and protein) was significantly reduced (P < 0.01). Protein expressions of TGF-β1, Col-IV, FN and caspase-3, and RIF index or cell apoptosis index in GU group were markedly elevated compared with those in SHO group (all P < 0.01). The protein expression of PHB had a negative correlation with the protein expression of TGF-β1, Col-IV, FN or caspase-3, and RIF index or cell apoptosis index (each P < 0.01).

CONCLUSIONS

Less expression of PHB is associated with increased caspase-3 expression/cell apoptosis in RIF rats. However, further research is needed to determine the effect of PHB on caspase-3 expression/cell apoptosis and to determine the potential of PHB as a therapeutic target.

TGF-β-activated kinase-1: New insights into the mechanism of TGF-β signaling and kidney disease

Transforming growth factor-β (TGF-β) is a multifunctional cytokine that regulates a wide variety of cellular functions, including cell growth, cellular differentiation, apoptosis, and wound healing. TGF-β1, the prototype member of the TGF-β superfamily, is well established as a central mediator of renal fibrosis. In chronic kidney disease, dysregulation of expression and activation of TGF-β1 results in the relentless synthesis and accumulation of extracellular matrix proteins that lead to the development of glomerulosclerosis and tubulointerstitial fibrosis, and ultimately to end-stage renal disease. Therefore, specific targeting of the TGF-β signaling pathway is seemingly an attractive molecular therapeutic strategy in chronic kidney disease. Accumulating evidence demonstrates that the multifunctionality of TGF-β1 is connected with the complexity of its cell signaling networks. TGF-β1 signals through the interaction of type I and type II receptors to activate distinct intracellular pathways. Although the Smad signaling pathway is known as a canonical pathway induced by TGF-β1, and has been the focus of many previous reviews, importantly TGF-β1 also induces various Smad-independent signaling pathways. In this review, we describe evidence that supports current insights into the mechanism and function of TGF-β-activated kinase 1 (TAK1), which has emerged as a critical signaling molecule in TGF-β-induced Smad-independent signaling pathways. We also discuss the functional role of TAK1 in mediating the profibrotic effects of TGF-β1.

The critical role of TAK1 in accentuated epithelial to mesenchymal transition in obliterative bronchiolitis after lung transplantation

Therapies to limit or reverse fibrosis have proven unsuccessful, highlighting the need for a greater understanding of basic mechanisms that drive fibrosis and, in particular, the link between fibrosis and inflammation. It has been shown that pro-fibrotic transforming growth factor β1 (TGF-β1)-driven epithelial-to-mesenchymal transition (EMT) can be accentuated by tumor necrosis factor α (TNF-α). TGF-β-activated kinase 1 (TAK1) is activated by both TGF-β1 and TNF-α, activating both nuclear factor kappa-light-chain-enhancer of activated B cells and mitogen-activated protein kinase signaling pathways. In this study, we evaluated the potential for TAK1 to modulate the synergistic effect between TGF-β1 and TNF-α in driving EMT. Co-stimulation with TGF-β1 and TNF-α induced an accentuated and extended phosphorylation of TAK1 compared to either alone. TAK1 signaled downstream via nuclear factor kappa-light-chain-enhancer of activated B cells, and Jun N-terminal kinase-2, but independent of Jun N-terminal kinase-1, extracellular signal-regulated kinase-1/2, or p38 mitogen-activated protein kinase signaling to drive EMT in bronchial epithelial cells. Blocking either TAK1 or Jun N-terminal kinase-2 inhibited EMT. TAK1 phosphorylation was increased in the airway epithelium of patients with fibrotic airway disease. These data identify factors leading to and affected by accentuated and extended TAK1 phosphorylations potential novel therapeutic targets in inflammation-driven fibrotic diseases.

PTEN loss defines a TGF-β-induced tubule phenotype of failed differentiation and JNK signaling during renal fibrosis

We investigated the signaling basis for tubule pathology during fibrosis after renal injury. Numerous signaling pathways are activated physiologically to direct tubule regeneration after acute kidney injury (AKI) but several persist pathologically after repair. Among these, transforming growth factor (TGF)-β is particularly important because it controls epithelial differentiation and profibrotic cytokine production. We found that increased TGF-β signaling after AKI is accompanied by PTEN loss from proximal tubules (PT). With time, subpopulations of regenerating PT with persistent loss of PTEN (phosphate and tension homolog) failed to differentiate, became growth arrested, expressed vimentin, displayed profibrotic JNK activation, and produced PDGF-B. These tubules were surrounded by fibrosis. In contrast, PTEN recovery was associated with epithelial differentiation, normal tubule repair, and less fibrosis. This beneficial outcome was promoted by TGF-β antagonism. Tubule-specific induction of TGF-β led to PTEN loss, JNK activation, and fibrosis even without prior AKI. In PT culture, high TGF-β depleted PTEN, inhibited differentiation, and activated JNK. Conversely, TGF-β antagonism increased PTEN, promoted differentiation, and decreased JNK activity. Cre-Lox PTEN deletion suppressed differentiation, induced growth arrest, and activated JNK. The low-PTEN state with JNK signaling and fibrosis was ameliorated by contralateral nephrectomy done 2 wk after unilateral ischemia, suggesting reversibility of the low-PTEN dysfunctional tubule phenotype. Vimentin-expressing tubules with low-PTEN and JNK activation were associated with fibrosis also after tubule-selective AKI, and with human chronic kidney diseases of diverse etiology. By preventing tubule differentiation, the low-PTEN state may provide a platform for signals initiated physiologically to persist pathologically and cause fibrosis after injury.

Association of PAX2 with cell apoptosis in unilateral ureteral obstruction rats

Renal interstitial fibrosis (RIF) is the final common pathway for chronic kidney disease. Cell apoptosis is a critical detrimental event that leads to renal fibrosis. Paired box 2 (PAX2) plays a major role in the development of the kidney. This study was performed to investigate whether PAX2 was associated with cell apoptosis in the progression of RIF in unilateral ureteral obstruction (UUO) rats. Eighty Wistar male rats were divided into two groups randomly: sham operation group (SHO) and model group subjected to UUO (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected 14 and 28 days after surgery. Protein expressions of PAX2, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN), and caspase-3 were detected using immunohistochemical analysis; mRNA expression of PAX2 in renal tissue was detected by real-time reverse transcription polymerase chain reaction; and RIF index and cell apoptosis index in renal interstitium were also calculated. When compared with those in the SHO group, expressions of PAX2 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and RIF index and cell apoptosis index in the GU group were remarkably increased when compared with those in the SHO group (each p < 0.01). The protein expression of PAX2 was positively correlated with the protein expressions of TGF-β1, α-SMA, Col-IV, FN, and caspase-3 and with RIF index and cell apoptosis index (all p < 0.01). The apoptotic cell in our observation was mainly derived from renal tubular epithelial cells. In conclusion, the increased expression of PAX2 is associated with cell apoptosis in the progression of RIF in UUO rats, suggesting that PAX2 is a potentially therapeutic target for prevention of RIF. Tian-Biao Zhou and Yuan-Han Qin wish it to be known that, in their opinion, they should be regarded as joint first authors.