Peroxiredoxin V selectively regulates IL-6 production by modulating the Jak2-Stat5 pathway

Extracellular peroxiredoxin 5 exacerbates atherosclerosis via the TLR4/MyD88 pathway

BACKGROUNGD AND AIMS

Peroxiredoxin 5 (PRDX5), an atypical 2-Cys peroxiredoxin (PRDX), is known to regulate global oxidative stresses and inflammatory responses. Inflammation and oxidative stress are pivotal factors in the development of atherosclerosis, especially in the context of vascular endothelial dysfunction. However, effects of PRDX5 on atherosclerosis remain unclear. This study aimed to elucidate the role of PRDX5 in the pathogenesis of atherosclerosis.

METHODS

For in vivo analysis, normal chow diet 60-week old Apolipoprotein E knockout (ApoE-/-) and Prdx5-/-; ApoE-/- mice were used for the experiments. For in vitro analysis, human umbilical vein endothelial cells (HUVECs) were stimulated with oxidized LDL (oxLDL; 50 ng/ml) for 24hrs, following serum starvation by incubation with serum-free Endothelial Cell Growth Medium-2 (EGM-2) for 1hr.

RESULTS

We observed elevated PRDX5 expression under atherosclerotic conditions in both humans and mice. Unexpectedly, Prdx5-/-; ApoE-/- mice exhibited reduced plaque formation, with no discernible difference in aortic hydrogen peroxide (H2O2) levels compared to ApoE-/- mice. Additionally, there was a notable decrease in macrophage accumulation and vascular inflammation in the atherosclerotic aorta of Prdx5-/-; ApoE-/-. In vitro, HUVECs stimulated with oxLDL showed upregulated PRDX5 expression in both lysate and culture medium. Moreover, PRDX5 knockdown in oxLDL-stimulated (oxLDL-siPRDX5) HUVECs significantly reduced the migration and adhesion of human monocytic cells (THP-1) to HUVECs, indicating diminished vascular immune responses. Mechanistically, both in vivo and in vitro, PRDX5 deficiency inhibited the Toll-like receptor 4 (TLR4)/Myeloid differentiation primary response 88 (MyD88) signaling pathway, resulting in reduced nuclear factor kappa B (NF-κB) and P38 phosphorylation. Furthermore, treatment with recombinant PRDX5 (rPRDX5) protein restored TLR4/MyD88 signaling in oxLDL-siPRDX5 HUVECs.

CONCLUSIONS

These data demonstrate that extracellular PRDX5 contributes to endothelial inflammation, promoting macrophage accumulation in the atherosclerotic aorta through activation of TLR4/MyD88/NF-κB and P38 signaling pathways, thereby exacerbating the progression of atherosclerosis.

Peroxiredoxin 5 regulates osteogenic differentiation through interaction with hnRNPK during bone regeneration

Peroxiredoxin 5 (Prdx5) is involved in pathophysiological regulation via the stress-induced cellular response. However, its function in the bone remains largely unknown. Here, we show that Prdx5 is involved in osteoclast and osteoblast differentiation, resulting in osteoporotic phenotypes in Prdx5 knockout (Prdx5^Ko) male mice. To investigate the function of Prdx5 in the bone, osteoblasts were analyzed through immunoprecipitation (IP) and liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) methods, while osteoclasts were analyzed through RNA-sequencing. Heterogeneous nuclear ribonucleoprotein K (hnRNPK) was identified as a potential binding partner of Prdx5 during osteoblast differentiation in vitro. Prdx5 acts as a negative regulator of hnRNPK-mediated osteocalcin (Bglap) expression. In addition, transcriptomic analysis revealed that in vitro differentiated osteoclasts from the bone marrow-derived macrophages of Prdx5^Ko mice showed enhanced expression of several osteoclast-related genes. These findings indicate that Prdx5 might contribute to the maintenance of bone homeostasis by regulating osteoblast differentiation. This study proposes a new function of Prdx5 in bone remodeling that may be used in developing therapeutic strategies for bone diseases.

Molecular cloning, prokaryotic expression and the anti-inflammatory activity of porcine PRDX5

Peroxiredoxin 5 (PRDX5) is the sole member of the atypical 2-Cys subfamily of mammalian PRDXs, a family of thiol-dependent peroxidases. In addition to its antioxidant effect, PRDX5 has been implicated in modulating the inflammatory response. In this study, the full-length cDNA encoding porcine PRDX5 (pPRDX5) was cloned. Subsequently, using porcine alveolar macrophages (PAMs), the target cells of PRRSV infection in vivo, we found that the recombinant pPRDX5 protein inhibited inflammatory responses induced by tumor necrosis factor alpha (TNF-α) or porcine reproductive and respiratory syndrome virus (PRRSV), a virus causing severe interstitial pneumonia in pigs. By contrast, knockdown of endogenous pPRDX5 with specific siRNA enhanced inflammatory responses induced by TNF-α or PRRSV. We also demonstrated that the involvement of pPRDX5 in inflammation regulation depended on its peroxidase activity. Taken together, these results showed that pPRDX5 is an anti-inflammatory molecule, which may play an important immune-regulation role in the pathogenicity of PRRSV.

Macrophage polarization is involved in liver fibrosis induced by β 1-adrenoceptor autoantibody

Accumulating evidence suggests that liver injury can be induced by the over-expression of β ₁-adrenergic receptors (β ₁-ARs). High titers of autoantibodies specific to β ₁-adrenergic receptors (β ₁-AA) are detected in the sera of heart failure patients, potentially playing agonist-like roles. However, the role of β ₁-AA in liver function has not been characterized. In this study, we collect the sera of primary biliary cholangitis (PBC) patients, a condition which easily develops into liver fibrosis, and analyze the relationship between PBC and β ₁-AA. A passive immunization model is established to assess the effect of β ₁-AA on the liver. Subsequently, the effect of β ₁-AA on macrophages is investigated in vitro. Results show that PBC patients have a high titer and ratio of β ₁-AA, compared to controls. Liver injury and fibrosis are induced by β ₁-AA. In vitro experiments with ROS probe demonstrate that β ₁-AA induces macrophages to produce ROS and secrete TNFα. These effects can be partially reversed by metoprolol, a blocker for β ₁-AR. Results from the transwell and phagocytosis assays show that β ₁-AA promotes macrophage migration and phagocytosis. FCM tests suggest that β ₁-AA induces the alteration of M1 rather than M2 markers in macrophages. Finally, the Annexin V/PI assay indicates that macrophage culture supernatants stimulated by β ₁-AA cause hepatocyte apoptosis. Overall, these results suggest that β ₁-AA is involved in PBC. The β ₁-AA-induced activation, phagocytosis and phenotypic modification of macrophages may play an important role in the development of hepatic fibrosis and injury.

IL-6: The Link Between Inflammation, Immunity and Breast Cancer

Breast cancer is one of the leading causes of mortality in females. Over the past decades, intensive efforts have been made to uncover the pathogenesis of breast cancer. Interleukin-6 (IL-6) is a pleiotropic factor which has a vital role in host defense immunity and acute stress. Moreover, a wide range of studies have identified the physiological and pathological roles of IL-6 in inflammation, immune and cancer. Recently, several IL-6 signaling pathway-targeted monoclonal antibodies have been developed for cancer and immune therapy. Combination of IL-6 inhibitory antibody with other pathways blockage drugs have demonstrated promising outcome in both preclinical and clinical trials. This review focuses on emerging studies on the strong linkages of IL-6/IL-6R mediated regulation of inflammation and immunity in cancer, especially in breast cancer.

Chamaecyparis obtusa (Siebold & Zucc.) Endl. leaf extracts prevent inflammatory responses via inhibition of the JAK/STAT axis in RAW264.7 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Chamaecyparis obtusa (Siebold & Zucc.) Endl. (C. obtusa) has been used as folk medicine in East Asia and has been reported to alleviate inflammatory diseases. However, the detailed mechanisms for the anti-inflammatory effects of C. obtusa remain unclear.

AIM OF THE STUDY

Although the anti-inflammatory mechanisms of natural products have been studied for decades, it is still important to identify the potential anti-inflammatory effects of natural sources. In this study, we investigated the anti-inflammatory effects and underlying mechanism of C. obtusa leaf extracts.

MATERIAL &METHODS

The cell viability was determined by MTT and crystal violet staining. NO production in the supernatant was measured using Griess reagent. The cell lysates were analyzed by immunoblotting and RT-qPCR. Secreted cytokines were analyzed using ELISA kit and cytokine array kit. mRNA expression from the GSE9632 database set. Z-scores were calculated for each gene and visualized by heat map.

RESULTS

Among the extracts of C. obtusa obtained with different extraction methods, the 99% ethanol leaf extract (CO99EL) strongly inhibited lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression and Janus kinase/signaling transducer and activator of transcription (JAK/STAT) phosphorylation in RAW264.7 cells. In addition, CO99EL strongly inhibited LPS-induced interleukin (IL)-1β, IL-6, IL-27, and C-C motif chemokine ligand (CCL)-1 production and directly inhibited LPS-induced JAK/STAT phosphorylation in RAW264.7 cells.

CONCLUSIONS

These findings demonstrate that CO99EL significantly prevents LPS-induced macrophage activation by inhibiting the JAK/STAT axis. Therefore, we suggest the use of C. obtusa extracts as therapeutic approach for inflammatory diseases.

Ablation of Peroxiredoxin V Exacerbates Ischemia/Reperfusion-Induced Kidney Injury in Mice

Ischemia/reperfusion (I/R) is one of the major causes of acute kidney injury (AKI) and associated with increased mortality and progression to chronic kidney injury (CKI). Molecular mechanisms underlying I/R injury involve the production and excessive accumulation of reactive oxygen species (ROS). Peroxiredoxin (Prx) V, a cysteine-dependent peroxidase, is located in the cytosol, mitochondria, and peroxisome and has an intensive ROS scavenging activity. Therefore, we focused on the role of Prx V during I/R-induced AKI using Prx V knockout (KO) mice. Ablation of Prx V augmented tubular damage, apoptosis, and declined renal function. Prx V deletion also showed higher susceptibility to I/R injury with increased markers for oxidative stress, ER stress, and inflammation in the kidney. Overall, these results demonstrate that Prx V protects the kidneys against I/R-induced injury.

A key metabolic integrator, coenzyme A, modulates the activity of peroxiredoxin 5 via covalent modification

Peroxiredoxins (Prdxs) are antioxidant enzymes that catalyse the breakdown of peroxides and regulate redox activity in the cell. Peroxiredoxin 5 (Prdx5) is a unique member of Prdxs, which displays a wider subcellular distribution and substrate specificity and exhibits a different catalytic mechanism when compared to other members of the family. Here, the role of a key metabolic integrator coenzyme A (CoA) in modulating the activity of Prdx5 was investigated. We report for the first time a novel mode of Prdx5 regulation mediated via covalent and reversible attachment of CoA (CoAlation) in cellular response to oxidative and metabolic stress. The site of CoAlation in endogenous Prdx5 was mapped by mass spectrometry to peroxidatic cysteine 48. By employing an in vitro CoAlation assay, we showed that Prdx5 peroxidase activity is inhibited by covalent interaction with CoA in a dithiothreitol-sensitive manner. Collectively, these results reveal that human Prdx5 is a substrate for CoAlation in vitro and in vivo, and provide new insight into metabolic control of redox status in mammalian cells.

Peroxiredoxin V (PrdxV) negatively regulates EGFR/Stat3-mediated fibrogenesis via a Cys48-dependent interaction between PrdxV and Stat3

Activation of the epidermal growth factor receptor (EGFR)/signal transducer and activator of transcription 3 (Stat3) signaling pathway has been reported to be associated with renal fibrosis. We have recently demonstrated that peroxiredoxin V (PrdxV) acted as an antifibrotic effector by inhibiting the activity of Stat3 in TGF-β-treated NRK49F cells. However, the underlying mechanism of PrdxV remains poorly understood. To investigate molecular mechanism of PrdxV, we used a transgenic mouse model expressing PrdxV siRNA (PrdxVsi mice) and performed unilateral ureteral obstruction (UUO) for 7 days. 209/MDCT cells were transiently transfected with HA-tagged WT PrdxV and C48S PrdxV. Transgenic PrdxVsi mice displayed an exacerbated epithelial-to-mesenchymal transition (EMT) as well as an increase in oxidative stress induced by UUO. In the UUO kidney of the PrdxVsi mouse, knockdown of PrdxV increased Tyr1068-specific EGFR and Stat3 phosphorylation, whereas overexpression of WT PrdxV in 209/MDCT cells showed the opposite results. Immunoprecipitation revealed the specific interaction between WT PrdxV and Stat3 in the absence or presence of TGF-β stimulation, whereas no PrdxV-EGFR or C48S PrdxV-Stat3 interactions were detected under any conditions. In conclusion, PrdxV is an antifibrotic effector that sustains renal physiology. Direct interaction between PrdxV and Stat3 through Cys48 is a major molecular mechanism.

Enrichment of ATP Binding Proteins Unveils Proteomic Alterations in Human Macrophage Cell Death, Inflammatory Response, and Protein Synthesis after Interaction with Candida albicans

Macrophages are involved in the primary human response to Candida albicans. After pathogen recognition, signaling pathways are activated, leading to the production of cytokines, chemokines, and antimicrobial peptides. ATP binding proteins are crucial for this regulation. Here, a quantitative proteomic and phosphoproteomic approach was carried out for the study of human macrophage ATP-binding proteins after interaction with C. albicans. From a total of 547 nonredundant quantified proteins, 137 were ATP binding proteins and 59 were detected as differentially abundant. From the differentially abundant ATP-binding proteins, 6 were kinases (MAP2K2, SYK, STK3, MAP3K2, NDKA, and SRPK1), most of them involved in signaling pathways. Furthermore, 85 phosphopeptides were quantified. Macrophage proteomic alterations including an increase of protein synthesis with a consistent decrease in proteolysis were observed. Besides, macrophages showed changes in proteins of endosomal trafficking together with mitochondrial proteins, including some involved in the response to oxidative stress. Regarding cell death mechanisms, an increase of antiapoptotic over pro-apoptotic signals is suggested. Furthermore, a high pro-inflammatory response was detected, together with no upregulation of key mi-RNAs involved in the negative feedback of this response. These findings illustrate a strategy to deepen the knowledge of the complex interactions between the host and the clinically important pathogen C. albicans.

Rapid peroxynitrite reduction by human peroxiredoxin 3: Implications for the fate of oxidants in mitochondria

Mitochondria are main sites of peroxynitrite formation. While at low concentrations mitochondrial peroxynitrite has been associated with redox signaling actions, increased levels can disrupt mitochondrial homeostasis and lead to pathology. Peroxiredoxin 3 is exclusively located in mitochondria, where it has been previously shown to play a major role in hydrogen peroxide reduction. In turn, reduction of peroxynitrite by peroxiredoxin 3 has been inferred from its protective actions against tyrosine nitration and neurotoxicity in animal models, but was not experimentally addressed so far. Herein, we demonstrate the human peroxiredoxin 3 reduces peroxynitrite with a rate constant of 1 × 10⁷ M^-1 s^-1 at pH 7.8 and 25 °C. Reaction with hydroperoxides caused biphasic changes in the intrinsic fluorescence of peroxiredoxin 3: the first phase corresponded to the peroxidatic cysteine oxidation to sulfenic acid. Peroxynitrite in excess led to peroxiredoxin 3 hyperoxidation and tyrosine nitration, oxidative post-translational modifications that had been previously identified in vivo. A significant fraction of the oxidant is expected to react with CO₂ and generate secondary radicals, which participate in further oxidation and nitration reactions, particularly under metabolic conditions of active oxidative decarboxylations or increased hydroperoxide formation. Our results indicate that both peroxiredoxin 3 and 5 should be regarded as main targets for peroxynitrite in mitochondria.

Lipopolysaccharide promoted proliferation and adipogenesis of preadipocytes through JAK/STAT and AMPK-regulated cPLA2 expression

The proliferation and adipogenesis of preadipocytes played important roles in the development of adipose tissue and contributed much to the processes of obesity. On the other hand, lipopolysaccharide (LPS), also known as endotoxin, is a key outer membrane component of gram-negative bacteria in the gut microbiota, and has a dominant role in linking inflammation to high-fat diet-induced metabolic syndrome. Studies suggested the potential roles of LPS in hepatic steatosis and in obese mice models. However, the molecular mechanisms underlying LPS-regulated obesity remained largely unknown. Here we reported that LPS stimulated expression of cyosolic phospholipase A2 (cPLA2), one of inflammation regulators of obesity, in the preadipocytes. Pretreatment the inhibitors of JAK2, STAT3, STAT5 or AMPK significantly reduced LPS-increased mRNA and protein expression of cPLA2 together with phosphorylation of JAK2, STAT3, STAT5 and AMPK, separately. Similarly, transfection of siRNA against JAK2 or AMPK abolished expression of cPLA2 and phosphorylation of JAK2 or AMPK together with downregulated expression of JAK2 and AMPK protein. LPS enhanced activation of STAT3 and STAT5 via JAK2-dependent manner in the preadipocytes. Transfection of JAK2 or AMPK siRNA further proofed the independence of JAK2 and AMPK in LPS-treated preadipocytes. In addition, LPS-increased DNA synthesis, cell numbers and cell viability of preadipocytes were attenuated by AACOCF3, AG490, BML-275, cPLA2 siRNA, JAK2 siRNA or AMPK siRNA. Attenuation JAK2/STAT or AMPK-dependent cPLA2 expression reduced LPS-mediated adipogenesis of preadipocytes. Stimulation of arachidonic acid or AMPK activator, A-769662, increased cell numbers and cell viability and promoted differentiation of preadipocytes. Collectively, these results indicated that LPS increased preadipocytes proliferation and adipogenesis via JAK/STAT and AMPK-dependent cPLA2 expression. The mechanisms of LPS-stimulated cPLA2 expression may be a link between bacteria and obesity and provides the molecular basis for preventing metabolic syndrome or hyperplasic obesity.

Comparative estimation of sulfiredoxin levels between chronic periodontitis and healthy patients - A case-control study

BACKGROUND

Growing evidence suggests that oxidative stress forms a key component in the etiopathogenesis of periodontitis. Studies have shown potential antioxidants responsible for combating the pro-oxidants which stress the periodontium. But, peroxiredoxin-sulfiredoxin system is the least explored in periodontal disease.

METHODS

A case-control study was conducted on 30 participants who fulfilled the inclusion criteria from the Department of Periodontics, Saveetha Dental College and Hospital, Chennai, India. The patients were divided into two groups: 1) Group A- healthy controls (n = 18), 2) Group B- patients with generalized chronic periodontitis (n = 17). Following clinical examination, gingival tissue samples were procured from both the groups and subjected to protein quantification by Lowry method. The samples with adequate protein concentration (n = 30) from the two groups were further analyzed by enzyme-linked immunosorbent assay for estimation of sulfiredoxin levels.

RESULTS

Sulfiredoxin levels were significantly higher in the gingival tissues of chronic periodontitis patients (171.20 ± 16.97 ng/mL) than in healthy controls (131.20 ± 22.87) with P < 0.001. Also, the levels of sulfiredoxin in gingival tissue of periodontitis patients positively correlated with site-specific probing depth (r = 0.67; P = 0.007) and clinical attachment level (r = 0.55; P = 0.035).

CONCLUSIONS

The present study was a novel attempt to estimate the levels of sulfiredoxin which was significantly elevated in the diseased sites of patients with chronic periodontitis. Future studies are required to probe the role of sulfiredoxin in the etiopathogenesis of periodontal disease.

Peroxiredoxins in inflammatory liver diseases and ischemic/reperfusion injury in liver transplantation

Peroxiredoxins (Prxs) belong to the superfamily of thiol-dependent peroxidases, and remove reactive oxygen species (ROS) and other oxidative stress products. The expression and activity of Prxs can be substantially affected by stimuli from the microenvironment, and in turn regulate cytokine secretion in the context of inflammation in both peroxidase-dependent and -independent pathways. Prxs translocate to mitochondria and are hyperoxidized during acute liver damage, and attenuate intracellular ROS accumulation through their peroxidase activity. In particularly, Prx1 modulates the microenvironment in liver injuries by reducing adhesion molecule expression in vascular endothelial cells and inhibiting the inflammatory response and adhesion of macrophages. Prxs have potent prosurvival effects against ROS in ischemic/reperfusion (I/R) injury, but Prxs released from necrotic cells increase secretion of inflammatory cytokines by macrophages through TLR2 and 4 activation, which promotes cell death. Prxs can be used as biomarkers to evaluate I/R injury and predict graft survival in liver transplantation. Prxs are modulated in various types of chronic hepatitis and hepatosteatosis, and mediate disease progression. Alcohol administration increases oxidization and inactivation of Prxs in mice because of oxidative stress. In conclusion, Prxs are essential mediators and biomarkers in inflammatory liver diseases and I/R injury.

Genetics of primary sclerosing cholangitis and pathophysiological implications

Primary sclerosing cholangitis (PSC) is a chronic disease leading to fibrotic scarring of the intrahepatic and extrahepatic bile ducts, causing considerable morbidity and mortality via the development of cholestatic liver cirrhosis, concurrent IBD and a high risk of bile duct cancer. Expectations have been high that genetic studies would determine key factors in PSC pathogenesis to support the development of effective medical therapies. Through the application of genome-wide association studies, a large number of disease susceptibility genes have been identified. The overall genetic architecture of PSC shares features with both autoimmune diseases and IBD. Strong human leukocyte antigen gene associations, along with several susceptibility genes that are critically involved in T-cell function, support the involvement of adaptive immune responses in disease pathogenesis, and position PSC as an autoimmune disease. In this Review, we survey the developments that have led to these gene discoveries. We also elaborate relevant interpretations of individual gene findings in the context of established disease models in PSC, and propose relevant translational research efforts to pursue novel insights.

Peroxiredoxin 5 (Prx5) decreases LPS-induced microglial activation through regulation of Ca2+/calcineurin-Drp1-dependent mitochondrial fission

Microglial activation is a hallmark of neurodegenerative diseases. ROS activates microglia by regulating transcription factors to express pro-inflammatory genes and is associated with disruption of Ca²⁺ homeostasis through thiol redox modulation. Recently, we reported that Prx5 can regulate activation of microglia cells by governing ROS. In addition, LPS leads to excessive mitochondrial fission, and regulation of mitochondrial dynamics involved in a pro-inflammatory response is important for the maintenance of microglial activation. However, the precise relationship among these signals and the role of Prx5 in mitochondrial dynamics and microglial activation is still unknown. In this study, we demonstrated that Ca²⁺/calcineurin-dependent de-phosphorylation of Drp1 induces mitochondrial fission and regulates mitochondrial ROS production, which influences the expression of pro-inflammatory mediators in LPS-induced microglia cells. Moreover, it is likely that cytosolic and Nox-derived ROS were upstream of mitochondrial fission and mitochondrial ROS generation in activated microglia cells. Prx5 regulates LPS-induced mitochondrial fission through modulation of Ca²⁺/calcineurin-dependent Drp1 de-phosphorylation by eliminating Nox-derived and cytosolic ROS. Therefore, we suggest that mitochondrial dynamics may be essential for understanding pro-inflammatory responses and that Prx5 may be used as a new therapeutic target to prevent neuroinflammation and neurodegenerative diseases.

Peroxiredoxin 5 Protects TGF-β Induced Fibrosis by Inhibiting Stat3 Activation in Rat Kidney Interstitial Fibroblast Cells

Renal fibrosis is a common final pathway of end-stage kidney disease which is induced by aberrant accumulation of myofibroblasts. This process is triggered by reactive oxygen species (ROS) and proinflammatory cytokines generated by various source of injured kidney cells. Peroxiredoxin 5 (Prdx5) is a thiol-dependent peroxidase that reduces oxidative stress by catalyzing intramolecular disulfide bonds. Along with its antioxidant effects, expression level of Prdx5 also was involved in inflammatory regulation by immune stimuli. However, the physiological effects and the underlying mechanisms of Prdx5 in renal fibrosis have not been fully characterized. Sprague-Dawley rats were subjected to unilateral ureteral obstruction (UUO) for 1 or 7 days. For the in vitro model, NRK49F cells, a rat kidney interstitial fibroblast cell lines, were treated with transforming growth factor β (TGF-β) for 0, 1, 3, or 5 days. To access the involvement of its peroxidase activity in TGF-β induced renal fibrosis, wild type Prdx5 (WT) and double mutant Prdx5 (DM), converted two active site cysteines at Cys 48 and Cys 152 residue to serine, were transiently expressed in NRK49F cells. The protein expression of Prdx5 was reduced in UUO kidneys. Upregulation of fibrotic markers, such as fibronectin and alpha-smooth muscle actin (α-SMA), declined at 5 days in time point of higher Prdx5 expression in TGF-β treated NRK49F cells. The overexpression of wild type Prdx5 by transient transfection in NRK49F cells attenuated the TGF-β induced upregulation of fibronectin and α-SMA. On the other hand, the transient transfection of double mutant Prdx5 did not prevent the activation of fibrotic markers. Overexpression of Prdx5 also suppressed the TGF-β induced upregulation of Stat3 phosphorylation, while phosphorylation of Smad 2/3 was unchanged. In conclusion, Prdx5 protects TGF-β induced fibrosis in NRK49F cells by modulating Stat3 activation in a peroxidase activity dependent manner.

Multiple Roles of Peroxiredoxins in Inflammation

Inflammation is a pathophysiological response to infection or tissue damage during which high levels of reactive oxygen and nitrogen species are produced by phagocytes to kill microorganisms. Reactive oxygen and nitrogen species serve also in the complex regulation of inflammatory processes. Recently, it has been proposed that peroxiredoxins may play key roles in innate immunity and inflammation. Indeed, peroxiredoxins are evolutionarily conserved peroxidases able to reduce, with high rate constants, hydrogen peroxide, alkyl hydroperoxides and peroxynitrite which are generated during inflammation. In this minireview, we point out different possible roles of peroxiredoxins during inflammatory processes such as cytoprotective enzymes against oxidative stress, modulators of redox signaling, and extracellular pathogen- or damage-associated molecular patterns. A better understanding of peroxiredoxin functions in inflammation could lead to the discovery of new therapeutic targets.

Interaction of peroxiredoxin V with dihydrolipoamide branched chain transacylase E2 (DBT) in mouse kidney under hypoxia

Background

Peroxiredoxin V (Prdx V) plays a major role in preventing oxidative damage as an effective antioxidant protein within a variety of cells through peroxidase activity. However, the function of Prdx V is not limited to peroxidase enzymatic activity per se. It appears to have unique function in regulating cellular response to external stimuli by directing interaction with signaling protein. In this study, we identified Prdx V interacting partners in mouse kidney under hypoxic stress using immunoprecipitation and shotgun proteomic analysis (LC-MS/MS).

Results

Immunoprecipitation coupled with nano-UPLC-MS^E shotgun proteomics was employed to identify putative interacting partners of Prdx V in mouse kidney in the setting of hypoxia. A total of 17 proteins were identified as potential interacting partners of Prdx V by a comparative interactomics analysis in kidney under normoxia versus hypoxia. Dihydrolipoamide branched chain transacylase E2 (DBT) appeared to be a prominent candidate protein displaying enhanced interaction with Prdx V under hypoxic stress. Moreover, hypoxic kidney exhibited altered DBT enzymatic activity compared to normoxia. An enhanced colocalization of these two proteins under hypoxic stress was successfully observed in vitro. Furthermore, peroxidatic cysteine residue (Cys48) of Prdx V is likely to be responsible for interacting with DBT.

Conclusions

We identified several proteins interacting with Prdx V under hypoxic condition known to induce renal oxidative stress. In hypoxic condition, we observed an enhanced interaction of Prdx V and DBT protein as well as increased DBT enzymatic activity. The results from this study will contribute to enhance our understanding of Prdx V’s role in hypoxic stress and may suggest new directions for future research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-014-0061-2) contains supplementary material, which is available to authorized users.