Cyclosporin A and tacrolimus induce renal Erk1/2 pathway via ROS-induced and metalloproteinase-dependent EGF-receptor signaling

Role of Oxidative Stress in the Occurrence and Development of Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) causes recurrent apnea and intermittent hypoxia at night, leading to several complications such as cognitive dysfunction. However, the molecular mechanisms underlying cognitive dysfunction in OSAS are unclear, and oxidative stress mediated by intermittent hypoxia is an important mechanism. In addition, the improvement of cognitive dysfunction in patients with OSAS varies by different treatment regimens; among them, continuous positive airway pressure therapy (CPAP) is mostly recognized for improving cognitive dysfunction. In this review, we discuss the potential mechanisms of oxidative stress in OSAS, the common factors of affecting oxidative stress and the Links between oxidative stress and inflammation in OSAS, focusing on the potential links between oxidative stress and cognitive dysfunction in OSAS and the potential therapies for neurocognitive dysfunction in patients with OSAS mediated by oxidative stress. Therefore, further analysis on the relationship between oxidative stress and cognitive dysfunction in patients with OSAS will help to clarify the etiology and discover new treatment options, which will be of great significance for early clinical intervention.

Probenecid ameliorates testosterone-induced benign prostatic hyperplasia: Implications of PGE-2 on ADAM-17/EGFR/ERK1/2 signaling cascade

Benign prostatic hyperplasia (BPH) is one of the most prevalent clinical disorders in the elderly. Probenecid (Prob) is a well-known FDA-approved therapy for gout owing to its uricosuric effect. The present study evaluated the use of Prob for BPH as a COX-2 inhibitor. Prob (100 and 200 mg/kg) was intraperitoneally injected into male Wistar rats daily for 3 weeks. In the second week, testosterone (3 mg/kg) was subcutaneously injected to induce BPH. Compared with BPH-induced rats, Prob treatment reduced prostate weight and index and improved histopathological architecture. The protease activity of ADAM-17/TACE and its ligands (TGF-α and TNF-α) were regulated by prob, which in turn abolished EGFR phosphorylation, and several inflammatory mediators (COX-2, PGE2, NF-κB (p65), and IL-6) were suppressed. By reducing the nuclear import of extracellular regulated kinase protein 1/2 (ERK1/2), Prob helped re-establish the usual equilibrium between antiapoptotic proteins like Bcl-2 and cyclin D1 and proapoptotic proteins like Bax. All of these data point to Prob as a promising treatment for BPH because of its ability to inhibit COX-2-syntheiszed PGE2 and control the ADAM-17/TGF-α-induced EGFR/ERK1/2 signaling cascade. These findings might help to repurpose Prob for the treatment of BPH.

Ca2+-mediated mitochondrial inner membrane permeabilization induces cell death independently of Bax and Bak

The ability of mitochondria to buffer a rapid rise in cytosolic Ca²⁺ is a hallmark of proper cell homeostasis. Here, we employed m-3M3FBS, a putative phospholipase C (PLC) agonist, to explore the relationships between intracellular Ca²⁺ imbalance, mitochondrial physiology, and cell death. m-3M3FBS induced a potent dose-dependent Ca²⁺ release from the endoplasmic reticulum (ER), followed by a rise in intra-mitochondrial Ca²⁺. When the latter exceeded the organelle buffering capacity, an abrupt mitochondrial inner membrane permeabilization (MIMP) occurred, releasing matrix contents into the cytosol. MIMP was followed by cell death that was independent of Bcl-2 family members and inhibitable by the intracellular Ca²⁺ chelator BAPTA-AM. Cyclosporin A (CsA), capable of blocking the mitochondrial permeability transition (MPT), completely prevented cell death induced by m-3M3FBS. However, CsA acted upstream of mitochondria by preventing Ca²⁺ release from ER stores. Therefore, loss of Ca²⁺ intracellular balance and mitochondrial Ca²⁺ overload followed by MIMP induced a cell death process that is distinct from Bcl-2 family-regulated mitochondrial outer membrane permeabilization (MOMP). Further, the inhibition of cell death by CsA or its analogues can be independent of effects on the MPT.

Impact of the ACE2 activator xanthenone on tacrolimus nephrotoxicity: Modulation of uric acid/ERK/p38 MAPK and Nrf2/SOD3/GCLC signaling pathways

AIMS

The calcineurin inhibitor tacrolimus is an effective and widely used immunosuppressant after organ transplantation to reduce graft rejection. However, its nephrotoxic effect could compel the patients to treatment discontinuation. The beneficial effects of angiotensin-converting enzyme 2 (ACE2) on the kidney and other organs have been investigated in several studies, but its role in tacrolimus nephrotoxicity still needs to be elucidated. Our study was designed to investigate effects of the ACE2 activator xanthenone on tacrolimus-induced renal injury.

MATERIALS AND METHODS

Male Wistar rats were administered xanthenone (2 mg/kg) concurrently with tacrolimus (1 mg/kg) for 3 weeks, then blood and kidney tissue samples were collected for biochemical and molecular investigations.

KEY FINDINGS

Co-administration of xanthenone significantly improved renal functions in tacrolimus-treated rats, where serum creatinine, urea, and uric acid levels were close to those of the normal control. Besides, xanthenone reduced renal angiotensin (ANG) II content, while elevated ANG (1-7). Relative protein expressions of p-ERK/ERK and p-p38 MAPK/p38 MAPK inflammatory signals were downregulated upon xanthenone administration with tacrolimus. In addition, xanthenone reinforced antioxidant defense against tacrolimus by enhancing protein expression of the transcription factor Nrf2 with subsequently increased mRNA expressions of the antioxidants SOD3 and GCLC.

SIGNIFICANCE

These protective effects of xanthenone could be attributed to ANG II degradation to ANG (1-7) by ACE2 activation resulting in regulated inflammatory and oxidative responses in the kidney. Therefore, administration of xanthenone along with tacrolimus could be a promising therapeutic strategy to reduce the adverse effects and increase the tolerability to tacrolimus immunosuppressive therapy.

ADAMs family in kidney physiology and pathology

A disintegrin and metalloproteinases (ADAMs) family are proteolytic transmembrane proteases that modulate diverse cell functions and coordinate intercellular communication. ADAMs are responsible for regulating cell proliferation, differentiation, migration, and organ morphogenesis in kidney development. Abnormally activated ADAMs drive inflammation and fibrosis in response to kidney diseases such as acute kidney injury, diabetic kidney disease, polycystic kidney disease, and chronic allograft nephropathy. ADAM10 and ADAM17, known as the most characterized members of ADAMs, are extensively investigated in kidney diseases. Notably, ADAM proteases have the potential to be targets for developing novel treatment approaches in kidney diseases.

Camel Milk Mitigates Cyclosporine-Induced Renal Damage in Rats: Targeting p38/ERK/JNK MAPKs, NF-κB, and Matrix Metalloproteinases

Renal damage is a devastating adverse effect for cyclosporine; a widely used immunosuppressant drug. The present work examined the potential of camel milk, a natural agent with marked anti-inflammatory/antioxidant properties, to attenuate cyclosporine-induced renal injury. The kidney tissue was examined with the aid of Western blotting, immunohistochemistry, biochemical assays, including colorimetric and ELISA kits. The present findings revealed that camel milk (10 mL/kg/day; for 3 weeks by gavage) significantly lowered serum creatinine, BUN, and KIM-1 renal dysfunction markers. Mechanistically, camel milk inhibited renal inflammation, as seen by significant decrease of the pro-inflammatory cytokines (MCP-1, TNF-α, IL-1β, and IL-18) and extracellular degradation signals (MMP-2 and MMP-9) and enhanced the generation of the anti-inflammatory IL-10. Moreover, it inhibited the upstream pro-inflammatory p38/ERK/JNK MAPK pathway by lowering the phosphorylation of the 3 subfamilies of MAPKs (p38 MAPK, JNK1/2, and ERK1/2). Furthermore, camel milk curbed the NF-κB pathway activation by downregulating the protein expression of activated NF-κBp65, p-NF-κBp65, and p-IκBα proteins. Additionally, camel milk inhibited renal oxidative stress by lowering the MPO activity and augmenting the reduced/oxidized glutathione ratio and total antioxidant capacity. These findings propose that camel milk may be a promising agent that inhibits cyclosporine-triggered renal inflammation via curtailing the p38/ERK/JNK MAPK and NF-κB pathways, matrix metalloproteinases, and pro-inflammatory cytokines.

Loss of Mitochondrial Control Impacts Renal Health

Disruption of mitochondrial biosynthesis or dynamics, or loss of control over mitochondrial regulation leads to a significant alteration in fuel preference and metabolic shifts that potentially affect the health of kidney cells. Mitochondria regulate metabolic networks which affect multiple cellular processes. Indeed, mitochondria have established themselves as therapeutic targets in several diseases. The importance of mitochondria in regulating the pathogenesis of several diseases has been recognized, however, there is limited understanding of mitochondrial biology in the kidney. This review provides an overview of mitochondrial dysfunction in kidney diseases. We describe the importance of mitochondria and mitochondrial sirtuins in the regulation of renal metabolic shifts in diverse cells types, and review this loss of control leads to increased cell-to-cell transdifferentiation processes and myofibroblast-metabolic shifts, which affect the pathophysiology of several kidney diseases. In addition, we examine mitochondrial-targeted therapeutic agents that offer potential leads in combating kidney diseases.

PEG-SOD attenuates the mitogenic ERK1/2 signaling cascade induced by cyclosporin A in the liver and kidney of albino mice

The calcineurin inhibitor, cyclosporin A (CsA) is one of the most common immunosuppressive agents used in organ transplantation. However, its clinical use is often limited by several unwanted effects including nephrotoxicity and hepatotoxicity. By using immunohistochemical and ELISA techniques, it was found that CsA administration causes a rapid activation of a disintegrin and metalloproteases-17 (ADAM-17), epidermal growth factor receptor (EGFR) and subsequent ERK1/2 phosphorylation in the liver and kidney of albino mice. Furthermore, this study presents mechanistic relevance of this signaling cascade involving reactive oxygen species (ROS)-mediated ADAM-17/EGFR/ERK1/2 activation as indicated by a clear reduction in ADAM-17 and EGFR activities as well as ERK1/2 phosphorylation when the animals pretreated with Polyethylene glycol-superoxide dismutase (PEG-SOD) before CsA administration. Collectively, our findings demonstrate that CsA has the ability to activate ADAM-17-mediated EGFR/ERK1/2 phosphorylation in the liver and kidney of albino mice in ROS-dependent manner. Finally, these data may support the concept of using antioxidant therapy as a valuable approach for the prevention of CsA-induced nephrotoxicity and hepatotoxicity.

Cyclosporin A activates human hepatocellular carcinoma (HepG2 cells) proliferation: implication of EGFR-mediated ERK1/2 signaling pathway

One of the most common causes of cancer mortality worldwide is hepatocellular carcinoma (HCC). Extracellular signal-regulated kinase (ERK1/2) pathway has been shown to play an important role in the development and progression of HCC. Here, we demonstrate that the immunosuppressive agent cyclosporin A (CsA) has the ability to increase the cellular growth in HCC (HepG2 cells) via activation of ERK1/2 signaling cascade. It was found that ERK1/2 phosphorylation induced by CsA was highly reduced in the presence of the reactive oxygen species (ROS) scavenger polyethylene glycol-superoxide dismutase (PEG-SOD). Furthermore, it was observed that inhibition of metalloproteinase activity using TAPI-2 prevents ERK1/2 activation by CsA. Moreover, a disintegrin and metalloproteinase domain 17 (ADAM-17) activity was found to be critical for ERK phosphorylation by CsA. In addition, CsA-induced ERK phosphorylation was highly reduced in the presence of either neutralizing anti-heparin-binding-epidermal growth factor (HB-EGF) antibody or UO126 (MEK inhibitor). By using the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478, it was found that EGFR is critical for ERK phosphorylation induced by CsA. Furthermore, CsA-induced cell proliferation was strongly reduced in the presence of either PEG-SOD or TAPI-2 or neutralizing anti-ADAM17 antibody or neutralizing anti-HB-EGF antibody or AG1478 or UO126. Collectively, these data demonstrate that CsA has the ability to activate ERK1/2 signaling cascade that could be translated into an increase in HepG2 cell proliferation. Furthermore, these data support the role of ROS, ADAM-17, and EGFR in ERK1/2 signaling activation and subsequent cell proliferation induced by CsA in HepG2 cells.

Activation of renal profibrotic TGFβ controlled signaling cascades by calcineurin and mTOR inhibitors

The calcineurin inhibitors (CNI) cyclosporine A (CsA) and tacrolimus represent potent immunosuppressive agents frequently used for solid organ transplantation and treatment of autoimmune disorders. Despite of their immense therapeutic benefits, residual fibrosis mainly in the kidney represents a common side effect of long-term therapy with CNI. Regardless of the immunosuppressive action, an increasing body of evidence implicates that a drug-induced increase in TGFβ and subsequent activation of TGFβ-initiated signaling pathways is closely associated with the development and progression of CNI-induced nephropathy. Mechanistically, an increase in reactive oxygen species (ROS) generation due to drug-induced changes in the intracellular redox homeostasis functions as an important trigger of the profibrotic signaling cascades activated under therapy with CNI. Although, inhibitors of the mechanistic target of rapamycin (mTOR) kinase have firmly been established as alternative compounds with a lower nephrotoxic potential, an activation of fibrogenic signaling cascades has been reported for these drugs as well. This review will comprehensively summarize recent advances in the understanding of profibrotic signaling events modulated by these widely used compounds with a specific focus put on mechanisms occurring independent of their respective immunosuppressive action. Herein, the impact of redox modulation, the activation of canonical TGFβ and non-Smad pathways and modulation of autophagy by both classes of immunosuppressive drugs will be highlighted and discussed in a broader perspective. The comprehensive knowledge of profibrotic signaling events specifically accompanying the immunomodulatory activity of these widely used drugs is needed for a reliable benefit-risk assessment under therapeutic regimens.

Calcineurin inhibitor-induced complement system activation via ERK1/2 signalling is inhibited by SOCS-3 in human renal tubule cells

One factor that significantly contributes to renal allograft loss is chronic calcineurin inhibitor (CNI) nephrotoxicity (CIN). Among other factors, the complement (C-) system has been proposed to be involved CIN development. Hence, we investigated the impact of CNIs on intracellular signalling and the effects on the C-system in human renal tubule cells. In a qPCR array, CNI treatment upregulated C-factors and downregulated SOCS-3 and the complement inhibitors CD46 and CD55. Additionally, ERK1/-2 was required for these regulations. Following knock-down and overexpression of SOCS-3, we found that SOCS-3 inhibits ERK1/-2 signalling. Finally, we assessed terminal complement complex formation, cell viability and apoptosis. Terminal complement complex formation was induced by CNIs. Cell viability was significantly decreased, whereas apoptosis was increased. Both effects were reversed under complement component-depleted conditions. In vivo, increased ERK1/-2 phosphorylation and SOCS-3 downregulation were observed at the time of transplantation in renal allograft patients who developed a progressive decline of renal function in the follow-up compared to stable patients. The progressive cohort also had lower total C3 levels, suggesting higher complement activity at baseline. In conclusion, our data suggest that SOCS-3 inhibits CNI-induced ERK1/-2 signalling, thereby blunting the negative control of C-system activation.

Therapeutic Effects of FK506 on IgA Nephropathy Rat

BACKGROUND/AIMS

FK506 is an immunosuppressive drug and a calcineurin inhibitor that has been widely used in kidney disease in recent years. FK506 shows a wide range of biological and pharmaceutical effects; however, the mechanism of its anti- proliferative effect has not been well elucidated. An IgA nephropathy (IgAN) model was used to generate a mesangial cell proliferation model. This study aims to examine the effect of FK506 on IgAN rats and the underlying mechanisms.

METHODS

Hematuria, proteinuria and renal function were measured. To observe the pathological conditions, we performed HE (hematoxylin - eosin) and PAS (periodic acid - schiff) staining. Transcription and protein expression levels were detected by qRT - PCR (quantitative real-time polymerase chain reaction) and Wb (western blotting). The location and semi-quantitative expression levels of TRPCs, CaN (Calcineurin) and α-SMA were examined by IHC (Immunohistochemical staining).

RESULTS

We found that FK506 could improve hematuria, proteinuria and renal function, especially in the HF (high-dose FK506) groups. Renal pathological changes were ameliorated in the treatment groups. FK506 could significantly decrease TRPCs, CaN, phosphorylation of ERK1/2 and α-SMA expression.

CONCLUSION

Taken together, these results suggest that the therapeutic effect of FK506 on IgAN might be partially associated with the down-regulated expression of TRPC channels, CaN and phosphorylation of ERK1/2.

Inhibition of calcineurin by FK506 stimulates germinal vesicle breakdown of mouse oocytes in hypoxanthine-supplemented medium

Calcineurin (CN) is a serine/threonine phosphatase which plays important roles in meiosis maturation in invertebrate oocytes; however, the role of CN in mouse oocytes is relatively unexplored. In this study, we examined the expression, localization and functional roles of CN in mouse oocytes and granulosa cells. The RT-PCR results showed that the β isoform of calcineurin A subunit (Cn A) expressed significantly higher than α and γ isoforms, and the expression of Cn Aβ mRNA obviously decreased in oocytes in which germinal vesicle breakdown (GVBD) occurred, while only B1 of calcineurin B subunit (Cn B) was detected in oocytes and stably expressed during oocytes maturation. The following fluorescence experiment showed that Cn A was mainly located in the nucleus of germinal vesicle (GV) stage oocytes and gruanlosa cells, and subsequently dispersed into the entire cytoplasm after GVBD. The decline of Cn A in oocytes suggested that it may play an important role in GVBD. To further clarify the role of calcineurin during meiotic maturation, FK506 (a calcineurin inhibitor) was used in the culture medium contained hypoxanthine (HX) which could keep mouse oocytes staying at GV stage. As expected, FK506 could induce a significant elevation of GVBD rate and increase the MPF level of denuded oocytes (DOs). Furthermore, FK506 could also play an induction role of GVBD of oocytes in COCs and follicles, and the process could be counteracted by MAPK kinase inhibitor (U0126). Above all, the results implied that calcineurin might play a crucial role in development of mouse oocytes and MPF and MAPK pathways are involved in this process.

Positioning of Tacrolimus for the Treatment of Diabetic Nephropathy Based on Computational Network Analysis

Objective

To evaluate tacrolimus as therapeutic option for diabetic nephropathy (DN) based on molecular profile and network-based molecular model comparisons.

Materials and Methods

We generated molecular models representing pathophysiological mechanisms of DN and tacrolimus mechanism of action (MoA) based on literature derived data and transcriptomics datasets. Shared enriched molecular pathways were identified based on both model datasets. A newly generated transcriptomics dataset studying the effect of tacrolimus on mesangial cells in vitro was added to identify mechanisms in DN pathophysiology. We searched for features in interference between the DN molecular model and the tacrolimus MoA molecular model already holding annotation evidence as diagnostic or prognostic biomarker in the context of DN.

Results

Thirty nine molecular features were shared between the DN molecular model, holding 252 molecular features and the tacrolimus MoA molecular model, holding 209 molecular features, with six additional molecular features affected by tacrolimus in mesangial cells. Significantly affected molecular pathways by both molecular model sets included cytokine-cytokine receptor interactions, adherens junctions, TGF-beta signaling, MAPK signaling, and calcium signaling. Molecular features involved in inflammation and immune response contributing to DN progression were significantly downregulated by tacrolimus (e.g. the tumor necrosis factor alpha (TNF), interleukin 4, or interleukin 10). On the other hand, pro-fibrotic stimuli being detrimental to renal function were induced by tacrolimus like the transforming growth factor beta 1 (TGFB1), endothelin 1 (EDN1), or type IV collagen alpha 1 (COL4A1).

Conclusion

Patients with DN and elevated TNF levels might benefit from tacrolimus treatment regarding maintaining GFR and reducing inflammation. TGFB1 and EDN1 are proposed as monitoring markers to assess degree of renal damage. Next to this stratification approach, the use of drug combinations consisting of tacrolimus in addition to ACE inhibitors, angiotensin receptor blockers, TGFB1- or EDN1-receptor antagonists might warrant further studies.

Calcineurin inhibitors cyclosporin A and tacrolimus protect against podocyte injury induced by puromycin aminonucleoside in rodent models

Podocyte injury and the appearance of proteinuria are features of minimal-change disease (MCD). Cyclosporin A (CsA) and tacrolimus (FK506) has been reported to reduce proteinuria in patients with nephrotic syndrome, but mechanisms remain unknown. We, therefore, investigated the protective mechanisms of CsA and FK506 on proteinuria in a rat model of MCD induced by puromycin aminonucleoside (PAN) and in vitro cultured mouse podocytes. Our results showed that CsA and FK506 treatment decreased proteinuria via a mechanism associated to a reduction in the foot-process fusion and desmin, and a recovery of synaptopodin and podocin. In PAN-treated mouse podocytes, pre-incubation with CsA and FK506 restored the distribution of the actin cytoskeleton, increased the expression of synaptopodin and podocin, improved podocyte viability, and reduced the migrating activities of podocytes. Treatment with CsA and FK506 also inhibited PAN-induced podocytes apoptosis, which was associated with the induction of Bcl-xL and inhibition of Bax, cleaved caspase 3, and cleaved PARP expression. Further studies revealed that CsA and FK506 inhibited PAN-induced p38 and JNK signaling, thereby protecting podocytes from PAN-induced injury. In conclusion, CsA and FK506 inhibit proteinuria by protecting against PAN-induced podocyte injury, which may be associated with inhibition of the MAPK signaling pathway.

Angiotensin-(1-7)/Mas Signaling Inhibits Lipopolysaccharide-Induced ADAM17 Shedding Activity and Apoptosis in Alveolar Epithelial Cells

A disintegrin and metalloproteinase (ADAM) 17, constitutively expressed in alveolar epithelium, is the pivotal shedding enzyme mediating acute lung inflammation. On the other hand, angiotensin (Ang)-(1-7)/Mas signaling has been shown to improve acute respiratory distress syndrome and protect alveolar epithelial cells from apoptosis. In this study, we explored the effect of Ang-(1-7)/Mas signaling on the expression and activity of ADAM17 and assessed its impact on apoptosis in lipopolysaccharide (LPS)-treated human alveolar epithelial cells. LPS markedly induced the shedding activity of ADAM17 in alveolar epithelial cells, which was blocked by selective c-Jun N-terminal kinase (JNK) inhibitor SP600125. Ang-(1-7) concentration-dependently inhibited LPS-induced ADAM17 shedding activity, which was abolished by selective Mas blocker A779 and Mas shRNA. LPS and Ang-(1-7) showed no significant effect on the expression of ADAM17. Overexpression of ADAM17 synergized with LPS on increasing the shedding activity of ADAM17 and apoptosis in alveolar epithelial cells, counteracting the inhibitory effects of Ang-(1-7). In addition, LPS significantly increased the JNK activity in alveolar epithelial cells; Ang-(1-7) concentration-dependently inhibited LPS-induced JNK activity, which was abolished by A779 and Mas shRNA. In conclusion, this study suggests that Ang-(1-7)/Mas signaling inhibits LPS-induced alveolar epithelial cell apoptosis by inhibiting LPS-induced shedding activity of ADAM17, likely by a JNK-dependent mechanism.

Hippocampal mitogen-activated protein kinase activation is associated with intermittent hypoxia in a rat model of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS), characterized by intermittent hypoxia/re-oxygenation, may impair the cerebral system. Although mitogen-activated protein kinase (MAPK) signaling was observed to have a key role in hypoxia-induced brain injury, the intracellular events and their underlying mechanisms for intermittent hypoxia/re-oxygenation-associated damage to hippocamal MAPKs, including extracellular signal-regulated kinase (ERK)1/2, P38MAPK and c-Jun N-terminal kinase (JNK) remain to be elucidated and require further investigation. A total of five rats in each sub-group were exposed to intermittent hypoxia or continued hypoxia for 2, 4, 6 or 8 weeks. Histological, immunohistochemical and biological analyses were performed to assess nerve cell injury in the hippocampus. Surviving CA1 pyramidal cells were identified by hematoxylin and eosin staining. The levels of phosphorylated ERK1/2, P38MAPK and JNK were detected by western blotting. B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) in neural cells were examined by immunohistochemistry. The malondialdehyde (MDA) contents and superoxide dismutase (SOD) activities were measured by thiobarbituric acid and xanthine oxidation methods, respectively. Under continued hypoxia, the levels of phospho-ERK1/2 peaked at the fourth week and then declined, whereas phospho-P38MAPK and JNK were detected only in the late stages. By contrast, under intermittent hypoxia, ERK1/2, P38MAPK and JNK were activated at all time-points assessed (2, 4, 6 and 8 weeks). The levels of phospho-ERK1/2, P38MAPK and JNK were all higher in the intermittent hypoxia groups than those in the corresponding continued hypoxia groups. Bcl-2 was mainly increased and reached the highest level at six weeks in the continued hypoxia group. Of note, Bcl-2 rapidly increased to the peak level at four weeks, followed by a decrease to the lowest level at the eighth week in the intermittent hypoxia group. Bax was generally increased at the late stages under continued hypoxia, but increased at all time-points under the intermittent hypoxia conditions. The two types of hypoxia induced an increase in the MDA content, but a decrease in SOD activity. Marked changes in these two parameters coupled with markedly reduced surviving cells in the hippocampus in a time-dependent manner were observed in the intermittent hypoxia group in comparison with the continued hypoxia group. OSAS-induced intermittent hypoxia markedly activated the MAPK signaling pathways, which were triggered by oxidative stress, leading to abnormal expression of downstream Bcl-2 and Bax, and a severe loss of neural cells in the hippocampus.

Cyclosporin A promotes tumor angiogenesis in a calcineurin-independent manner by increasing mitochondrial reactive oxygen species

The widely used immunosuppressant cyclosporin A, a potent calcineurin inhibitor, significantly increases the incidence of cancer in organ transplant patients. Calcineurin signaling is an important mediator of VEGF signaling in endothelial cells. Negative regulation of calcineurin by its endogenous inhibitor, Down Syndrome Candidate Region-1 (DSCR1), suppresses tumor growth and angiogenesis, in contrast to the effect observed after long-term cyclosporin A treatment. Despite the significance of calcineurin signaling in endothelial cells, the consequences of cyclosporin A on tumor angiogenesis have not been investigated. Using an in vivo model of skin carcinogenesis, prolonged treatment with cyclosporin A promoted tumor growth and angiogenesis. The addition of cyclosporin A to endothelial cells in vitro increased proliferation and migration in a calcineurin-independent manner and is associated with increased mitochondrial reactive oxygen species (ROS). Co-treatment with antioxidants significantly abrogated cyclosporin A-induced endothelial cell activation. Furthermore, mice treated with antioxidants were protected against cyclosporin A-mediated tumor progression. Taken together, these findings suggest that cyclosporin A affects endothelial cells in a calcineurin-independent manner to potentiate tumor growth by promoting tumor angiogenesis through increasing mitochondrial ROS production. This work identifies a previously undescribed mechanism underlying a significantly adverse off-target effect of cyclosporin A and suggests that co-treatment with antioxidants would inhibit the tumor-promoting effects of cyclosporin A.

IMPLICATIONS

Targeting the proangiogenic effects of cyclosporin A may be useful in the management of transplant-associated cancers.

The pentachlorophenol metabolite tetrachlorohydroquinone induces massive ROS and prolonged p-ERK expression in splenocytes, leading to inhibition of apoptosis and necrotic cell death

Pentachlorophenol (PCP) has been used extensively as a biocide and a wood preservative and has been reported to be immunosuppressive in rodents and humans. Tetrachlorohydroquinone (TCHQ) is a major metabolite of PCP. TCHQ has been identified as the main cause of PCP-induced genotoxicity due to reactive oxidant stress (ROS). However, the precise mechanisms associated with the immunotoxic effects of PCP and TCHQ remain unclear. The aim of this study was to examine the effects of PCP and TCHQ on the induction of ROS and injury to primary mouse splenocytes. Our results shown that TCHQ was more toxic than PCP and that a high dose of TCHQ led to necrotic cell death of the splenocytes through induction of massive and sudden ROS and prolonged ROS-triggered ERK activation. Inhibition of ROS production by N-acetyl-cysteine (NAC) partially restored the mitochondrial membrane potential, inhibited ERK activity, elevated caspase-3 activity and PARP cleavage, and, eventually, switched the TCHQ-induced necrosis to apoptosis. We suggest that prolonged ERK activation is essential for TCHQ-induced necrosis, and that ROS play a pivotal role in the different TCHQ-induced cell death mechanisms.

ADAM17 mediates Nox4 expression and NADPH oxidase activity in the kidney cortex of OVE26 mice

Matrix protein accumulation is a prominent feature of diabetic nephropathy that contributes to renal fibrosis and decline in renal function. The pathogenic mechanisms of matrix accumulation are incompletely characterized. We investigated if the matrix metalloprotease a disintegrin and metalloprotease1 7 (ADAM17), known to cleave growth factors and cytokines, is activated in the kidney cortex of OVE26 type 1 diabetic mice and the potential mechanisms by which ADAM17 mediates extracellular matrix accumulation. Protein expression and activity of ADAM17 were increased in OVE26 kidney cortex. Using a pharmacological inhibitor to ADAM17, TMI-005, we determined that ADAM17 activation results in increased type IV collagen, Nox4, and NADPH oxidase activity in the kidney cortex of diabetic mice. In cultured mouse proximal tubular epithelial cells (MCTs), high glucose increases ADAM17 activity, Nox4 and fibronectin expression, cellular collagen content, and NADPH oxidase activity. These effects of glucose were inhibited when cells were pretreated with TMI-005 and/or transfected with small interfering ADAM17. Collectively, these data indicate a novel mechanism whereby hyperglycemia in diabetes increases extracellular matrix protein expression in the kidney cortex through activation of ADAM17 and enhanced oxidative stress through Nox enzyme activation. Additionally, our study is the first to provide evidence that Nox4 is downstream of ADAM17.

Transforming growth factor-β1 induces matrix metalloproteinase-9 expression in rat vascular smooth muscle cells via ROS-dependent ERK-NF-κB pathways

Both matrix metalloproteinase-9 (MMP9) and transforming growth factors-β1 (TGF-β1) are the important factors in the pathogenesis of the aortic aneurysm (AA) and aortic dissection (AD). Recent studies have shown that inhibition of reactive oxygen species (ROS) production, extracellular signal-regulated kinase 1/2(ERK1/2) or NF-κB pathways is able to suppress aneurysm formation. The median layers of arterial walls are mainly the vascular smooth muscle cells (VSMCs), while the pathogenesis of AA and AD is closely related to the changes in the median layer structure. Thus, we investigated the molecular mechanisms underlying TGF-β1-induced MMP-9 expression in VSMC, the involvement of intracellular ROS and signaling molecules, including ERK1/2 and NF-κB. Rat vascular smooth muscle cells (A7r5) were used. MMP-9 expression was analyzed by gelatin zymography, western blot and RT-PCR. The involvement of intracellular ROS and signaling molecules including ERK1/2 and NF-κB in the responses was investigated using reactive oxygen scavenger N-acetylcysteine (NAC) and pharmacological inhibitors (U0126 and BAY11-7082), determined by ROS testing and western blot testing for their corresponding proteins. TGF-β1 induces MMP-9 expression via ROS-dependent signaling pathway. ROS production leads to activation of ERK1/2 and then activation of the NF-κB transcription factor. Activated NF-κB turns on transcription of the MMP-9 gene. The process in which TGF-β1 induces MMP9 expression involves the ROS-dependent ERK-NF-κB signal pathways in VSMC. This discovery raises a new regulation pathway in the VSMC, and it shows the potential to help to find a new solution to treating aortic aneurysm and aortic dissection.

Galloflavin, a new lactate dehydrogenase inhibitor, induces the death of human breast cancer cells with different glycolytic attitude by affecting distinct signaling pathways

Galloflavin (GF), a recently identified lactate dehydrogenase inhibitor, hinders the proliferation of cancer cells by blocking glycolysis and ATP production. The aim of the present experiments was to study the effect of this compound on breast cancer cell lines reproducing different pathological subtypes of this tumor: MCF-7 (the well differentiated form), MDA-MB-231 (the aggressive triple negative tumor) and MCF-Tam (a sub-line of MCF-7 with acquired tamoxifen resistance). We observed marked differences in the energetic metabolism of these cell lines. Compared to MCF-7 cells, both MDA-MB-231 and MCF-Tam cells exhibited higher LDH levels and glucose uptake and showed lower capacity of oxygen consumption. In spite of these differences, GF exerted similar growth inhibitory effects. This result was explained by the finding of a constitutively activated stress response in MDA-MB-231 and MCF-Tam cells, which reproduce the poor prognosis tumor forms. As a further proof, different signaling pathways were found to be involved in the antiproliferative action of GF. In MCF-7 cells we observed a down regulation of the ERα-mediated signaling needed for cell survival. On the contrary, in MCF-Tam and MDA-MB-231 cells growth inhibition appeared to be contributed by an oxidative stress condition. The prevalent mechanism of cell death was found to be apoptosis induction. Because of the clinical relevance of breast cancer forms having the triple negative and/or chemoresistant phenotype, our results showing comparable effects of GF even on aggressively growing cells encourage further studies to verify the potential of this compound in improving the chemotherapy of breast cancer.

Calcineurin inhibitors and immunosuppression - a tale of two isoforms

Organ transplantation is the state of the art for treating end-stage organ failure. Over 25000 organ transplants are performed in the USA each year. Survival rates following transplantation are now approaching 90% for 1 year and 75% for 5 years. Central to this success was the introduction of drugs that suppress the immune system and prevent rejection. The most commonly used class of immunosuppressing drugs are calcineurin inhibitors (CNIs). Calcineurin is a ubiquitous enzyme that is important for T-cell function. With more people taking CNIs for longer and longer periods of time the consequences of calcineurin inhibition on other organ systems - particularly the kidney - have become a growing concern. Virtually all people who take a CNI will develop some degree of kidney toxicity and up to 10% will progress to kidney failure. In the past 15 years, research into calcineurin action has identified distinct actions of the two main isoforms of the catalytic subunit of the enzyme. The α-isoform is required for kidney function whereas the β-isoform has a predominant role in the immune system. This review will discuss the current state of knowledge about calcineurin isoforms and how these new insights may reshape post-transplant immunosuppression.