Metformin Attenuates TGF-β1-Induced Fibrosis in Salivary Gland: A Preliminary Study

Fibrosis commonly arises from salivary gland injuries induced by factors such as inflammation, ductal obstruction, radiation, aging, and autoimmunity, leading to glandular atrophy and functional impairment. However, effective treatments for these injuries remain elusive. Transforming growth factor-beta 1 (TGF-β1) is fundamental in fibrosis, advancing fibroblast differentiation into myofibroblasts and enhancing the extracellular matrix in the salivary gland. The involvement of the SMAD pathway and reactive oxygen species (ROS) in this context has been postulated. Metformin, a type 2 diabetes mellitus (T2DM) medication, has been noted for its potent anti-fibrotic effects. Through human samples, primary salivary gland fibroblasts, and a rat model, this study explored metformin's anti-fibrotic properties. Elevated levels of TGF-β1 (p < 0.01) and alpha-smooth muscle actin (α-SMA) (p < 0.01) were observed in human sialadenitis samples. The analysis showed that metformin attenuates TGF-β1-induced fibrosis by inhibiting SMAD phosphorylation (p < 0.01) through adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-independent pathways and activating the AMPK pathway, consequently suppressing NADPH oxidase 4 (NOX4) (p < 0.01), a main ROS producer. Moreover, in rats, metformin not only reduced glandular fibrosis post-ductal ligation but also protected acinar cells from ligation-induced injuries, thereby normalizing the levels of aquaporin 5 (AQP5) (p < 0.05). Overall, this study underscores the potential of metformin as a promising therapeutic option for salivary gland fibrosis.

COL4A3 Mutation Induced Podocyte Apoptosis by Dysregulation of NADPH Oxidase 4 and MMP-2

Introduction

Podocyte apoptosis is a common mechanism driving progression in Alport syndrome (AS). This study aimed to investigate the mechanism of podocyte apoptosis caused by COL4A3 mutations.

Methods

We recruited patients with autosomal dominant AS (ADAS). Patients with minimal change disease (MCD) were recruited as controls. Microarray analysis was carried out on isolated glomeruli from the patients and validated. Then, corresponding mutant human podocytes (p.C1616Y) and 129 mice (p.C1615Y, the murine homolog to the human p.C1616Y) were constructed. The highest differentially expressed genes (DEGs) from microarray analysis were validated in transgenic mice and podocytes before and after administration of MMP-2 inhibitor (SB-3CT) and NOX4 inhibitor (GKT137831). We further validated NOX4/MMP-2/apoptosis pathway by real-time polymerase chain reaction (PCR), immunohistochemistry, and western blot in renal tissues from the ADAS patients.

Results

Using microarray analysis, we observed that DEGs, including NOX4/H2O2, MMP-2, and podocyte apoptosis-related genes were significantly upregulated. These genes were validated by real-time PCR, histologic analysis, and western blot in corresponding mutant human podocyte (p.C1616Y) and/or mice models (p.C1615Y). Moreover, we found podocyte apoptosis was abrogated and MMP-2 expression was down-regulated both in vivo and in vitro by NOX4 inhibition, urinary albumin-to-creatinine ratio, 24-hour proteinuria; and renal pathologic lesion was attenuated by NOX4 inhibition in vivo. Furthermore, podocyte apoptosis was attenuated whereas NOX4 expression remained the same by inhibition of MMP-2 both in vivo and in vitro.

Conclusion

These results indicated that NOX4 might induce podocyte apoptosis through the regulation of MMP-2 in patients with COL4A3 mutations. Our findings provided new insights into the mechanism of ADAS.

Peroxiredoxin 3 Inhibits Cardiac Fibrosis in Mice via NOX4-P38 Signalling

OBJECTIVE

Peroxiredoxin-3 (Prx-3) is widely acknowledged as an antioxidant that protects against mitochondrial reactive oxygen species. Nonetheless, its role in cardiac fibrosis has not been elucidated. We aim to explore the role and mechanism of Prx-3 in cardiac fibrosis.

MATERIALS AND METHODS

In this experimental study, mice received subcutaneous injections of isoproterenol (ISO) for 14 consecutive days (10 mg/kg/d for three days, followed by 5 mg/kg/d for 11 days) to establish a cardiac fibrosis model. The mice were subsequently injected with adenovirus-Prx-3 (ad-Prx-3) to enable Prx-3 overexpression. Echocardiography was used to evaluate cardiac function. Mice heart fibroblasts were isolated and stimulated with transforming growth factor β1 (TGFβ1) to induce fibrosis in vitro. Cells were also transfected with ad-Prx-3 for overexpression of Prx-3.

RESULTS

Echocardiographic diameters and fibrosis markers indicated that Prx-3 could inhibit ISO-induced cardiac dysfunction and fibrosis. Fibroblasts with Prx-3 overexpression exhibited reduced activation, proliferation, and collagen transcription. We found that Prx-3 reduced the expression of NADPH oxidase 4 (NOX4) and reduced P38 levels. After treatment with a P38 inhibitor, the Prx-3 overexpression-induced anti-fibrosis effect was mitigated.

CONCLUSION

Prx-3 could protect against ISO-induced cardiac fibrosis by inhibiting the NOX4-P38 pathway.

Modulation of Bleomycin-induced Oxidative Stress and Pulmonary Fibrosis by Ginkgetin in Mice via AMPK

BACKGROUND

Ginkgetin, a flavonoid extracted from Ginkgo biloba, has been shown to exhibit broad anti-inflammatory, anticancer, and antioxidative bioactivity. Moreover, the extract of Ginkgo folium has been reported on attenuating bleomycin-induced pulmonary fibrosis, but the anti-fibrotic effects of ginkgetin are still unclear. This study was intended to investigate the protective effects of ginkgetin against experimental pulmonary fibrosis and its underlying mechanism.

METHODS

In vivo, bleomycin (5 mg/kg) in 50 μL saline was administrated intratracheally in mice. One week after bleomycin administration, ginkgetin (25 or 50 mg/kg) or nintedanib (40 mg/kg) was administrated intragastrically daily for 14 consecutive days. In vitro, the AMPK-siRNA transfection in primary lung fibroblasts further verified the regulatory effect of ginkgetin on AMPK.

RESULTS

Administration of bleomycin caused characteristic histopathology structural changes with elevated lipid peroxidation, pulmonary fibrosis indexes, and inflammatory mediators. The bleomycin- induced alteration was normalized by ginkgetin intervention. Moreover, this protective effect of ginkgetin (20 mg/kg) was equivalent to that of nintedanib (40 mg/kg). AMPK-siRNA transfection in primary lung fibroblasts markedly blocked TGF-β1-induced myofibroblasts transdifferentiation and abolished oxidative stress.

CONCLUSION

All these results suggested that ginkgetin exerted ameliorative effects on bleomycininduced oxidative stress and lung fibrosis mainly through an AMPK-dependent manner.

Upregulation of Nox4 induces a pro-survival Nrf2 response in cancer-associated fibroblasts that promotes tumorigenesis and metastasis, in part via Birc5 induction

BACKGROUND

A pro-oxidant enzyme, NADPH oxidase 4 (Nox4) has been reported to be a critical downstream effector of TGFβ-induced myofibroblast transformation during fibrosis. While there are a small number of studies suggesting an oncogenic role of Nox4 derived from activated fibroblasts, direct evidence linking this pro-oxidant to the tumor-supporting CAF phenotype and the mechanisms involved are lacking, particularly in breast cancer.

METHODS

We targeted Nox4 in breast patient-derived CAFs via siRNA-mediated knockdown or administration of a pharmaceutical inhibitor (GKT137831). We also determine primary tumor growth and metastasis of implanted tumor cells using a stable Nox4-/- syngeneic mouse model. Autophagic flux of CAFs was assessed using a tandem fluorescent-tagged ptfl-LC3 plasmid via confocal microscopy analysis and determination of the expression level of autophagy markers (beclin-1 and LC3B). Nox4 overexpressing CAFs depend on the Nrf2 (nuclear factor-erythroid factor 2-related factor 2) pathway for survival. We then determined the dependency of Nox4-overexpressing CAFs on the Nrf2-mediated adaptive stress response pathway for survival. Furthermore, we investigated the involvement of Birc5 on CAF phenotype (viability and collagen contraction activity) as well as the expression level of CAF markers, FAP and αSMA.

CONCLUSIONS

We found that deletion of stroma Nox4 and pharmaceutically targeting its activity with GKT137831 significantly inhibited orthotopic tumor growth and metastasis of implanted E0771 and 4T1 murine mammary carcinoma cell lines in mice. More importantly, we found a significant upregulation of Nox4 expression in CAFs isolated from human breast tumors versus normal mammary fibroblasts (RMFs). Our in situ RNA hybridization analysis for Nox4 transcription on a human breast tumor microarray further support a role of this pro-oxidant in the stroma of breast carcinomas. In addition, we found that Nox4 promotes autophagy in CAFs. Moreover, we found that Nox4 promoted survival of CAFs via activation of Nrf2, a master regulator of oxidative stress response. We have further shown Birc5 is involved as a downstream modulator of Nrf2-mediated pro-survival phenotype. Together these studies indicate a role of redox signaling via the Nox4-Nrf2 pathway in tumorigenesis and metastasis of breast cancer cells by promoting autophagy and survival of CAFs.

NOX4: a potential therapeutic target for pancreatic cancer and its mechanism

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) is one of the seven isoforms of NOX family, which is upregulated in pancreatic cancer cell, mouse model of pancreatic cancer and human pancreatic cancer tissue. NOX4 is a constitutively active enzyme that primarily produces hydrogen peroxide, which exhibits completely different properties from other subtypes of NOX family. More importantly, recent studies illuminate that NOX4 promotes pancreatic cancer occurrence and development in different ways. This review summarizes the potential roles and its mechanism of NOX4 in pancreatic cancer and explores NOX4 as the potential therapeutic target in pancreatic cancer.

Modulation of Radiation-Induced NADPH Oxidases in Rat's Heart Tissues by Melatonin

Background

Experimental studies have shown that infiltration of inflammatory cells as well as upregulation of some cytokines play a central role in the development of late effects of ionizing radiation in heart tissues. Evidences have shown that an increased level of TGF-β has a direct correlation with late effects of exposure to ionizing radiation such as chronic oxidative stress and fibrosis. Recent studies have shown that TGF-β, through upregulation of pro-oxidant enzymes such as NOX2 and NOX4, promotes continuous ROS production and accumulation of fibrosis.

Objective

In present study, we aimed to evaluate the expression of NOX2 and NOX4 signaling pathways as well as possible modulatory effects of melatonin on the expression of these genes.

Material and Methods

In this experimental study, four groups of 20 rats (5 in each) were used as follows; G1: control; G2: melatonin; G3: radiation; G4: radiation + melatonin. 100 mg/kg of melatonin was administrated before irradiation of heart tissues with 15 Gy gamma rays. 10 weeks after irradiation, heart tissues were collected for real-time Polymerase chain reaction (PCR).

Results

Results showed a significant increase in the expression of TGF-β, Smad2, NF-kB, NOX2 and NOX4. The upregulation of NOX2 was more obvious by 20-fold compared to other genes. Except for TGF-β, melatonin could attenuate the expression of other genes.

Conclusion

This study indicated that exposure of rat's heart tissues to radiation leads to upregulation of TGF-β-NOX4 and TGF-β-NOX2 pathways. Melatonin, through modulation of these genes, may be able to alleviate radiation-induced chronic oxidative stress and subsequent consequences.

Activation of ERK1/2-mTORC1-NOX4 mediates TGF-β1-induced epithelial-mesenchymal transition and fibrosis in retinal pigment epithelial cells

Transforming growth factor-β (TGF-β) plays a crucial role in the development of epithelial to mesenchymal transition (EMT) and fibrosis, particularly in an ocular disorder such as proliferative vitreoretinopathy (PVR). However, the key molecular mechanism underlying its pathogenesis remains unknown. In the present study, using cultured ARPE-19 cells, we determined that TGF-β initiates a signaling pathway through extracellular signal-regulated kinase (ERK)-mammalian target of rapamycin complex 1 (mTORC1) that stimulates trans-differentiation and fibrosis of retinal pigment epithelium. Blocking this pathway by a TGF-βRI, ERK or mTORC1 inhibitor protected cells from EMT and fibrotic protein expression. TGF-β1 treatment increased reactive oxygen species (ROS) via NOX4 upregulation, which acts downstream of ERK and mTORC1, as the ROS scavenger N-acetylcysteine and a pan-NADPH oxidase (NOX) inhibitor DPI dissipated excess ROS generation. TGF-β1-induced oxidative stress resulted in EMT and fibrotic changes, as NAC and DPI prevented α-SMA, Col4α3 expression and cell migration. All these inhibitors blocked the downstream pathway activation in addition to clearly preventing the activation of its upstream molecules, indicating the presence of a feedback loop system that may boost the upstream events. Furthermore, the FDA-approved drug trametinib (10 nM) blunted TGF-β1-induced mTORC1 activation and downstream pathogenic alterations through ERK1/2 inhibition, which opens a therapeutic avenue for the treatment of PVR in the future.

The Hippo Pathway Effector TAZ Regulates Ferroptosis in Renal Cell Carcinoma

Despite recent advances, the poor outcomes in renal cell carcinoma (RCC) suggest novel therapeutics are needed. Ferroptosis is a form of regulated cell death, which may have therapeutic potential toward RCC; however, much remains unknown about the determinants of ferroptosis susceptibility. We found that ferroptosis susceptibility is highly influenced by cell density and confluency. Because cell density regulates the Hippo-YAP/TAZ pathway, we investigated the roles of the Hippo pathway effectors in ferroptosis. TAZ is abundantly expressed in RCC and undergoes density-dependent nuclear or cytosolic translocation. TAZ removal confers ferroptosis resistance, whereas overexpression of TAZS89A sensitizes cells to ferroptosis. Furthermore, TAZ regulates the expression of Epithelial Membrane Protein 1 (EMP1), which, in turn, induces the expression of nicotinamide adenine dinucleotide phosphate (NADPH) Oxidase 4 (NOX4), a renal-enriched reactive oxygen species (ROS)-generating enzyme essential for ferroptosis. These findings reveal that cell density-regulated ferroptosis is mediated by TAZ through the regulation of EMP1-NOX4, suggesting its therapeutic potential for RCC and other TAZ-activated tumors.

Regulation of thyroid sodium-iodide symporter in different stages of goiter: Possible involvement of reactive oxygen species

Na⁺ /I^- symporter (NIS) transports iodide into thyrocytes, a fundamental step for thyroid hormone biosynthesis. Our aim was to evaluate NIS regulation in different status of goitrogenesis and its underlying mechanisms. Wistar rats were treated with methimazole (MMI) for 5 and 21 days, to achieve different status of goiter. We then evaluated the effect of MMI removal for 1 day (R1d), after 5 (R1d-5d) or 21 (R1d-21d) days of MMI treatment. MMI increased thyroid weight, iodide uptake and in vitro TPO activity in a time-dependent way. Although MMI removal evoked a rapid normalization of TPO activity in R1d-5d, it was still high in R1d-21d. On the other hand, iodide uptake was rapidly down-regulated in R1d-21d, but not in R1d-5d, suggesting that the increased TPO activity in R1d-21d led to increased intraglandular organified iodine (I-X), which is known to inhibit iodide uptake. Since TGFβ has been shown to mediate some effects of I-X, we evaluated TGFβ and TGFβ receptor mRNA levels, which were increased in R1d-21d. Moreover, it has been demonstrated that TGFβ stimulates NOX4. Accordingly, our data revealed increased NOX4 expression and H₂ O₂ generation in R1d-21d. Finally, we evaluated the effect of H₂ O₂ on NIS function and mRNA levels in PCCL3 thyroid cell line, which were reduced. Thus, the present study suggests that there is a relationship between the size of the goiter and NIS regulation and that the mechanism might involve I-X, TGFβ, NOX4 and increased ROS production.

Endothelial NADPH oxidase 4 protects ApoE-/- mice from atherosclerotic lesions

Vascular reactive oxygen species (ROS) are known to be involved in atherosclerosis development and progression. NADPH oxidase 4 (Nox4) is a constitutively active ROS-producing enzyme that is highly expressed in the vascular endothelium. Nox4 is unique in its biology and has been implicated in vascular repair, however, the role of Nox4 in atherosclerosis is unknown. Therefore, to determine the effect of endothelial Nox4 on development of atherosclerosis, Apoe E-/- mice +/- endothelial Nox4 (ApoE-/- + EC Nox4) were fed a high cholesterol/high fat (Western) diet for 24 weeks. Significantly fewer atherosclerotic lesions were observed in the ApoE-/- + EC Nox4 mice as compared to the ApoE-/- littermates, which was most striking in the abdominal region of the aorta. In addition, markers of T cell populations were markedly different between the groups; T regulatory cell marker (FoxP3) was increased whereas T effector cell marker (T-bet) was decreased in aorta from ApoE-/- + EC Nox4 mice compared to ApoE-/- alone. We also observed decreased monokine induced by gamma interferon (MIG; CXCL9), a cytokine known to recruit and activate T cells, in plasma and tissue from ApoE-/- + EC Nox4 mice. To further investigate the link between endothelial Nox4 and MIG expression, we utilized cultured endothelial cells from our EC Nox4 transgenic mice and human cells with adenoviral overexpression of Nox4. In these cultured cells, upregulation of Nox4 attenuated endothelial cell MIG expression in response to interferon-gamma. Together these data suggest that endothelial Nox4 expression reduces MIG production and promotes a T cell distribution that favors repair over inflammation, leading to protection from atherosclerosis.