Improved mitochondrial function underlies the protective effect of pirfenidone against tubulointerstitial fibrosis in 5/6 nephrectomized rats

Oxidative Stress and Mitochondrial Dysfunction in Chronic Kidney Disease

The kidney contains many mitochondria that generate ATP to provide energy for cellular processes. Oxidative stress injury can be caused by impaired mitochondria with excessive levels of reactive oxygen species. Accumulating evidence has indicated a relationship between oxidative stress and kidney diseases, and revealed new insights into mitochondria-targeted therapeutics for renal injury. Improving mitochondrial homeostasis, increasing mitochondrial biogenesis, and balancing mitochondrial turnover has the potential to protect renal function against oxidative stress. Although there are some reviews that addressed this issue, the articles summarizing the relationship between mitochondria-targeted effects and the risk factors of renal failure are still few. In this review, we integrate recent studies on oxidative stress and mitochondrial function in kidney diseases, especially chronic kidney disease. We organized the causes and risk factors of oxidative stress in the kidneys based in their mitochondria-targeted effects. This review also listed the possible candidates for clinical therapeutics of kidney diseases by modulating mitochondrial function.

Administration of N-Acetylcysteine to Regress the Fibrogenic and Proinflammatory Effects of Oxidative Stress in Hypertrophic Ligamentum Flavum Cells

Ligamentum flavum hypertrophy (LFH) is a major cause of lumbar spinal stenosis (LSS). In hypertrophic ligamentum flavum (LF) cells, oxidative stress activates intracellular signaling and induces the expression of inflammatory and fibrotic markers. This study explored whether healthy and hypertrophic LF cells respond differently to oxidative stress, via examining the levels of phosphorylated p38 (p-p38), inducible nitric oxide synthase (iNOS), and α-smooth muscle actin (α-SMA). Furthermore, the efficacy of N-acetylcysteine (NAC), an antioxidant, in reversing the fibrogenic and proinflammatory effects of oxidative stress in hypertrophic LF cells was investigated by assessing the expression levels of p-p38, p-p65, iNOS, TGF-β, α-SMA, vimentin, and collagen I under H2O2 treatment with or without NAC. Under oxidative stress, p-p38 increased significantly in both hypertrophic and healthy LF cells, and iNOS was elevated in only the hypertrophic LF cells. This revealed that oxidative stress negatively affected both hypertrophic and healthy LF cells, with the hypertrophic LF cells exhibiting more active inflammation than did the healthy cells. After H2O2 treatment, p-p38, p-p65, iNOS, TGF-β, vimentin, and collagen I increased significantly, and NAC administration reversed the effects of oxidative stress. These results can form the basis of a novel therapeutic treatment for LFH using antioxidants.

Novel Preclinical Study of Galloylquinic Acid Compounds from Copaifera lucens with Potent Antifungal Activity against Vaginal Candidiasis Induced in a Murine Model via Multitarget Modes of Action

Vaginal candidiasis is a medical condition characterized by the overgrowth of Candida spp. in the vaginal cavity with complex recurrent pathogenicity as well as tolerance to antifungal therapy and hence is awaiting more safe and effective treatments. This work aimed to assess the potential antifungal activity of galloylquinic acid compounds (GQAs) from Copaifera lucens leaves against vaginal Candida albicans. The antifungal susceptibility test was performed against 20 isolates of multidrug-resistant (MDR) C. albicans using agar diffusion and broth microdilution assays. The results showed that GQAs exhibited strong antagonistic activity against the test isolates, with inhibition zone diameters ranging from 26 to 38 mm and low MICs (1 to 16 μg/mL) as well as minimum fungicidal concentrations (2 to 32 μg/mL). The MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay confirmed the safety of GQAs against the Vero cell line, showing a 50% inhibitory concentration (IC50) of 168.17 mg/mL. A marked difference in the growth pattern of the treated and untreated pathogens was also observed, where a concentration-dependent reduction in the growth rate occurred. Moreover, a pronounced fungicidal effect was demonstrated 6 h after treatment with 1× the minimum fungicidal concentration (MFC), as evidenced by time-kill assays, where the number of survivors was decreased a 6-fold. GQAs effectively inhibited and eradicated about 80% of C. albicans biofilm at 6 μg/mL and 32 μg/mL, respectively. Interestingly, GQAs disturbed the fungal membrane integrity, induced cell lysis, and reduced the virulence factors (proteinase and phospholipase) as well as the catalase activity. Moreover, the ergosterol content in the plasma membrane decreased in a concentration-dependent manner. Additionally, the altered mitochondrial membrane potential was associated with an increased release of cytochrome c from mitochondria to the cytosol, suggesting the initiation of early apoptosis in GQA-treated cells. Transcriptional analysis revealed that all test genes encoding virulence traits, including SAP1, PLB1, LIP1, HWP1, and ALS1, were markedly downregulated in GQA-treated cells compared to the control. The in vivo murine model of vaginal candidiasis further confirmed the therapeutic activity of GQAs (4 mg/kg of body weight) against C. albicans. This work comprehensively evaluated the antifungal, antivirulence, and antibiofilm activities of GQAs against C. albicans isolates using in vitro and in vivo models, providing molecular-level insights into the antifungal mechanism of action and experimental evidence that supports the potential use of GQAs for the treatment of vaginal candidiasis. IMPORTANCE Our work presents a new perspective on the potential use of GQAs as safe and highly effective phytochemicals against MDR C. albicans. This microorganism colonizes the human vaginal epithelium, causing vaginal candidiasis, a condition characterized by recurrent pathogenicity and tolerance to traditional antifungal therapy. Based on the results of in vitro tests, our study reports GQAs antifungal modes of action. These compounds exhibited an anticandidal effect by deactivating the fungal hydrolytic enzymes, reducing ergosterol content in the plasma membrane, altering the potential of the mitochondrial membrane, and inducing apoptosis. Additionally, GQAs showed high activity in eradicating the biofilm formed by the fungus via the downregulation of HWP1, ALS, SAP, PLB, and LIP genes, which are constitutively expressed in the biofilm. In an in vivo murine model of vaginal candidiasis, GQAs further demonstrated strong evidence of their effectiveness as an antifungal therapy. In this regard, our findings provide novel insights into the potential therapeutic use of these phytoactive molecules for vaginal candidiasis treatment.

Exercise Training Ameliorates Renal Oxidative Stress in Rats with Chronic Renal Failure

In patients with chronic kidney disease, exercise training with moderate intensity protects renal function and improves mortality. However, the mechanisms of the renal protective effects of exercise training in chronic kidney disease have not been clarified. This study investigated the effects of exercise training on renal NADPH oxidative and xanthine oxidase, which are major sources of reactive oxygen species, in rats with chronic renal failure. Six-week-old, male Sprague–Dawley rats were divided into the sham operation, 5/6 nephrectomy (Nx)+ sedentary, and Nx+ exercise training groups. The Nx+ exercise training group underwent treadmill running. After 12 weeks, systolic blood pressure, renal function, malondialdehyde, renal NADPH oxidase, and xanthine oxidase were examined. Nx induced hypertension, proteinuria, and renal dysfunction, and exercise training attenuated these disorders. Although the plasma levels of malondialdehyde were not different among the group, urinary levels were increased by Nx and decreased by exercise training. Renal activity and expression of NADPH oxidase and xanthine oxidase were increased by Nx and decreased by exercise training. These results indicate that exercise training attenuates hypertension and renal dysfunction and ameliorates NADPH oxidase and xanthine oxidase in rats with chronic renal failure, suggesting that the reduction of reactive oxygen species generation may be involved in the renal protective effects of exercise training.

Effect of pirfenidone protecting against cigarette smoke extract induced apoptosis

INTRODUCTION

Apoptosis of lung structural cells is a significant upstream event involved in COPD pathogenesis. This study was designed to explore whether pirfenidone (PFD) was able to attenuate apoptosis induced by cigarette smoke extract (CSE).

METHODS

A method of intraperitoneal CSE injection to BALB/C mice was used to establish emphysema mouse model. Terminal deoxynucleotidyl transferase dUTPnick end labeling (TUNEL) assay was applied to evaluate apoptotic cell ratio in mouse lung tissue. The cell viability of HBECs exposed to different concentrations of PFD was measured by Cell Counting Kit-8 (CCK-8) assay. The apoptosis index (AI) of HBECs was tested by flow cytometry. Levels of apoptosis-related protein were determined by Western blotting.

RESULTS

PFD treatment significantly decreased the AI value in emphysema mouse lung tissue by TUNEL. In HBECs, flow cytometry showed that PFD could significantly reduce AI led by CSE. Both in vitro and in vivo, protein levels of Bax and Cleaved-caspase 3 in CSE group significantly increased in contrast with the control group; while Bcl-2 protein level in CSE group was significantly decreased; moreover, PFD significantly reversed protein level changes of Bcl-2, Bax, and Cleaved-caspase 3 led by CSE.

CONCLUSIONS

This study reveals that PFD may potentially protect against CSE induced apoptosis.

Extracellular Vesicles in Redox Signaling and Metabolic Regulation in Chronic Kidney Disease

Chronic kidney disease (CKD) is a world health problem increasing dramatically. The onset of CKD is driven by several mechanisms; among them, metabolic reprogramming and changes in redox signaling play critical roles in the advancement of inflammation and the subsequent fibrosis, common pathologies observed in all forms of CKD. Extracellular vesicles (EVs) are cell-derived membrane packages strongly associated with cell-cell communication since they transfer several biomolecules that serve as mediators in redox signaling and metabolic reprogramming in the recipient cells. Recent studies suggest that EVs, especially exosomes, the smallest subtype of EVs, play a fundamental role in spreading renal injury in CKD. Therefore, this review summarizes the current information about EVs and their cargos’ participation in metabolic reprogramming and mitochondrial impairment in CKD and their role in redox signaling changes. Finally, we analyze the effects of these EV-induced changes in the amplification of inflammatory and fibrotic processes in the progression of CKD. Furthermore, the data suggest that the identification of the signaling pathways involved in the release of EVs and their cargo under pathological renal conditions can allow the identification of new possible targets of injury spread, with the goal of preventing CKD progression.

Exposure to Sub-Lethal Doses of Permethrin Is Associated with Neurotoxicity: Changes in Bioenergetics, Redox Markers, Neuroinflammation and Morphology

Permethrin (PERM) is a member of the class I family of synthetic pyrethroids. Human use has shown that it affects different systems, with wide health dysfunctions. Our aim was to determine bioenergetics, neuroinflammation and morphology changes, as redox markers after subacute exposure to PERM in rats. We used MDA determination, protein carbonyl assay, mitochondrial O₂ consumption, expression of pro-inflammatory cytokines and a deep histopathological analysis of the hippocampus. PERM (150 mg/kg and 300 mg/kg body weight/day, o.v.) increased lipoperoxidation and carbonylated proteins in a dose-dependent manner in the brain regions. The activities of antioxidant enzymes glutathione peroxidase, reductase, S-transferase, catalase, and superoxide dismutase showed an increase in all the different brain areas, with dose-dependent effects in the cerebellum. Cytokine profiles (IL-1β, IL-6 and TNF-α) increased in a dose-dependent manner in different brain tissues. Exposure to 150 mg/kg of permethrin induced degenerated and/or dead neurons in the rat hippocampus and induced mitochondrial uncoupling and reduction of oxidative phosphorylation and significantly decreased the respiratory parameters state 3-associated respiration in complex I and II. PERM exposure at low doses induces reactive oxygen species production and imbalance in the enzymatic antioxidant system, increases gene expression of pro-inflammatory interleukins, and could lead to cell damage mediated by mitochondrial functional impairment.

The Role of Interaction between Mitochondria and the Extracellular Matrix in the Development of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a condition which affects mainly older adults, that suggests mitochondrial dysfunction and oxidative stress, which follow cells senescence, and might contribute to the disease onset. We have assumed pathogenesis associated with crosstalk between the extracellular matrix (ECM) and mitochondria, mainly based on mitochondrial equilibrium impairment consisting of (1) tyrosine kinases and serine-threonine kinase (TKs and ST-Ks) activation via cytokines, (2) mitochondrial electron transport chain dysfunction and in consequence electrons leak with lower ATP synthesis, (3) the activation of latent TGF-β via αVβ6 integrin, (4) tensions transduction via α2β1 integrin, (5) inefficient mitophagy, and (6) stress inhibited biogenesis. Mitochondria dysfunction influences ECM composition and vice versa. Damaged mitochondria release mitochondrial reactive oxygen species (mtROS) and the mitochondrial DNA (mtDNA) to the microenvironment. Therefore, airway epithelial cells (AECs) undergo transition and secrete cytokines. Described factors initiate an inflammatory process with immunological enhancement. In consequence, local fibroblasts exposed to harmful conditions transform into myofibroblasts, produce ECM, and induce progression of fibrosis. In our review, we summarize numerous aspects of mitochondrial pathobiology, which seem to be involved in the pathogenesis of lung fibrosis. In addition, an increasing body of evidence suggests considering crosstalk between the ECM and mitochondria in this context. Moreover, mitochondria and ECM seem to be important players in the antifibrotic treatment of IPF.

Progressive Reduction in Mitochondrial Mass Is Triggered by Alterations in Mitochondrial Biogenesis and Dynamics in Chronic Kidney Disease Induced by 5/6 Nephrectomy

The five-sixth nephrectomy (5/6Nx) model is widely used to study the mechanisms involved in chronic kidney disease (CKD) progression. Mitochondrial impairment is a critical mechanism that favors CKD progression. However, until now, there are no temporal studies of the change in mitochondrial biogenesis and dynamics that allow determining the role of these processes in mitochondrial impairment and renal damage progression in the 5/6Nx model. In this work, we determined the changes in mitochondrial biogenesis and dynamics markers in remnant renal mass from days 2 to 28 after 5/6Nx. Our results show a progressive reduction in mitochondrial biogenesis triggered by reducing two principal regulators of mitochondrial protein expression, the peroxisome proliferator-activated receptor-gamma coactivator 1-alpha and the peroxisome proliferator-activated receptor alpha. Furthermore, the reduction in mitochondrial biogenesis proteins strongly correlates with the increase in renal damage markers. Additionally, we found a slow and gradual change in mitochondrial dynamics from fusion to fission, favoring mitochondrial fragmentation at later stages after 5/6Nx. Together, our results suggest that 5/6Nx induces the progressive reduction in mitochondrial mass over time via the decrease in mitochondrial biogenesis factors and a slow shift from mitochondrial fission to fusion; both mechanisms favor CKD progression in the remnant renal mass.

Protective effects and molecular mechanisms of Achyranthes bidentata polypeptide k on Schwann cells

Background

Achyranthes bidentata polypeptide k (ABPPk) is an active ingredient used in traditional Chinese medicine separated from Achyranthes bidentata polypeptides. So far, the role of ABPPk in peripheral nerve protection has not been comprehensively studied.

Methods

In this study, primary Schwann cells exposed to serum deprivation were treated with ABPPk or nerve growth factor (NGF) in vitro. Cell viability, cell apoptosis, apoptosis-related protein expression, and antioxidant enzyme activity were analyzed. To further explore the underlying molecular mechanisms and key regulatory molecules involved in the effects of ABPPk, integrative and dynamic bioinformatics analysis at different time points was carried out following RNA-seq of Schwann cells subjected to serum deprivation.

Results

We found that ABPPk could effectively reduce Schwann cell apoptosis caused by serum deprivation, which was comparable to NGF’s anti-apoptotic effects. ABPPk had the largest number of upregulated and downregulated differential expression genes at the earliest 0.5 h time, while NGF had fewer differential expression genes at this early stage. The significant difference at this time point between the two groups was also displayed in heatmaps. The molecular regulation of diseases and functions and canonical pathways revealed that ABPPk had more participation and advantages in the vasculature and immune system areas, especially angiogenesis regulation. Also, ABPPk demonstrated an earlier start in these molecular regulations than NGF. Furthermore, the analysis of transcription factors also illustrated that ABPPk not only had more key initial regulatory factors participating in vascular-related processes, but these also remained for a longer period. There was no significant difference in neural-related molecular regulation between the two groups.

Conclusions

Using high-throughput sequencing technology, our work unveiled the protective effects of ABPPk on Schwann cells after serum deprivation in a more comprehensive manner. These results further enrich the positive functions and molecular mechanisms of ABPPk and traditional Chinese medicine and benefit the discovery of novel therapeutic targets for peripheral nerve regeneration.

Lack of Autophagy Induction by Lithium Decreases Neuroprotective Effects in the Striatum of Aged Rats

The pharmacological modulation of autophagy is considered a promising neuroprotective strategy. While it has been postulated that lithium regulates this cellular process, the age-related effects have not been fully elucidated. Here, we evaluated lithium-mediated neuroprotective effects in young and aged striatum. After determining the optimal experimental conditions for inducing autophagy in loco with lithium carbonate (Li₂CO₃), we measured cell viability, reactive oxygen species (ROS) generation and oxygen consumption with rat brain striatal slices from young and aged animals. In the young striatum, Li₂CO₃ increased tissue viability and decreased ROS generation. These positive effects were accompanied by enhanced levels of LC3-II, LAMP 1, Ambra 1 and Beclin-1 expression. In the aged striatum, Li₂CO₃ reduced the autophagic flux and increased the basal oxygen consumption rate. Ultrastructural changes in the striatum of aged rats that consumed Li₂CO₃ for 30 days included electrondense mitochondria with disarranged cristae and reduced normal mitochondria and lysosomes area. Our data show that the striatum from younger animals benefits from lithium-mediated neuroprotection, while the striatum of older rats does not. These findings should be considered when developing neuroprotective strategies involving the induction of autophagy in aging.

Oxidative stress mediates age-related hypertrophy of ligamentum flavum by inducing inflammation, fibrosis, and apoptosis through activating Akt and MAPK pathways

The role of oxidative stress in ligamentum flavum (LF) hypertrophy has not been elucidated. We hypothesize that oxidative stress induces inflammatory responses and the subsequent fibrotic processes in LF, via activation of the Akt and MAPK pathways. Specimens of LFs were collected during surgeries for lumbar disc herniation (LDH) or lumbar spinal stenosis (LSS). Part of the LF specimens underwent analyses for ROS, fibrotic markers, and inflammatory mediators, with the remainder minced for cell cultures. The cell cultures were treated with H₂O₂, after which the cells were lysed and analyzed via western blotting. The specimens of the LSS patients showed increased infiltration of inflammatory cells and were stained positively for MMP-3, MMP-9, vimentin, and fibronectin. The LF of the LSS patients had increased oxidative stress and inflammation compared to that of the LDH patients. In vitro analyses demonstrated that oxidative stress rapidly activated the Akt and MAPK pathways. Inflammatory mediators, iNOS and NF-κB, and fibrotic markers, including TGF-β, β-catenin, α-SMA and vimentin, were significantly upregulated after induction of oxidative stress. Oxidative stress activated the intrinsic apoptotic pathway. These findings revealed that oxidative stress is one of the etiological factors of LF hypertrophy, which might provide new insights into treatment approaches.

Temporal Alterations in Mitochondrial β-Oxidation and Oxidative Stress Aggravate Chronic Kidney Disease Development in 5/6 Nephrectomy Induced Renal Damage

Five-sixths nephrectomy (5/6Nx) model is widely used for studying the mechanisms involved in chronic kidney disease (CKD) progression, a kidney pathology that has increased dramatically in recent years. Mitochondrial impairment is a key mechanism that aggravates CKD progression; however, the information on mitochondrial bioenergetics and redox alterations along a time course in a 5/6Nx model is still limited and in some cases contradictory. Therefore, we performed for the first time a time-course study of mitochondrial alterations by high-resolution respirometry in the 5/6Nx model. Our results show a decrease in mitochondrial β-oxidation at early times, as well as a permanent impairment in adenosine triphosphate (ATP) production in CI-linked respiration, a permanent oxidative state in mitochondria and decoupling of these organelles. These pathological alterations are linked to the early decrease in complex I and ATP synthase activities and to the further decrease in complex III activity. Therefore, our results may suggest that mitochondrial bioenergetics impairment is an early event in renal damage, whose persistence in time aggravates CKD development in the 5/6Nx model.

Renal protection of rhein against 5/6 nephrectomied-induced chronic kidney disease: role of SIRT3-FOXO3α signalling pathway

OBJECTIVES

The purpose of this study is to investigate the antifibrosis and anti-oxidation of rhein in vivo and in vitro, and to evaluate potential mechanisms involved in the treatment of chronic kidney disease (CKD).

METHODS

In experimental animal studies, CKD was established by 5/6 nephrectomy (5/6Nx). Serum creatinine (Scr) and blood urea nitrogen (BUN) were determined. Histopathologic tests were performed by HE and Masson trichrome stained. The level of ROS was investigated by fluorescence microplate with the probe 2', 7'-dichlorofluorescein diacetate (DCFH-DA). The protein expressions of p47phox and gp91phox were measured in 5/6Nx rats. In HK-2 cells, the expression of SIRT3 and Foxo3α was measured in SIRT3 knockdown conditions. The indicators of oxidation and fibrosisi were measured in SIRT3 knockdown conditions.

KEY FINDINGS

The results showed that, in addition to reducing renal interstitial pathologic injury and collagen fibrils, rhein administration improved renal function. The protective mechanisms were attributed to active SIRT3/FOXO3α signalling pathway and then play the anti-oxidative capacity of rhein, as well as to subsequent antifibrotic effect.

CONCLUSION

Taken together, rhein protected kidney through SIRT3/FOXO3a involvement. The anti-oxidative capacity of rhein contributed to the protective effects including the subsequent antifibrotic responses.

Pirfenidone attenuates homocysteine‑induced apoptosis by regulating the connexin 43 pathway in H9C2 cells

Pirfenidone (PFD) is an anti-fibrotic agent that is clinically used in the treatment of idiopathic pulmonary fibrosis. PFD has been shown to exert protective effects against damage to orbital fibroblasts, endothelial cells, liver cells and renal proximal tubular cells; however, its effect on myocardial cell apoptosis remains unclear. The present study aimed to characterize the effects of PFD on homocysteine (Hcy)-induced cardiomyocyte apoptosis and investigated the underlying mechanisms. H9C2 rat cardiomyocytes were pre-treated with PFD for 30 min followed by Hcy exposure for 24 h. The effects of PFD on cell cytotoxicity were evaluated by CCK-8 assay. The apoptosis rate of each group was determined by flow cytometry. The protein and mRNA levels of connexin 43 (Cx43), Bax, B-cell lymphoma-2 (Bcl-2) and caspase-3 were measured by western blot analysis and reverse transcription-quantitative PCR, respectively. The present results demonstrated that the apoptotic rate increased following Hcy exposure, whereas the apoptotic rate significantly decreased following PFD pre-treatment. Furthermore, the ratio of Bax/Bcl2 was upregulated following Hcy exposure, and Hcy upregulated the expression levels of cleaved caspase-3 and Cx43. Notably, these effects were prevented by PFD. Additionally, the effects of PFD were inhibited by the Cx43 agonist, AAP10. In summary, the findings of the present study demonstrate that PFD protects H9C2 rat cardiomyocytes against Hcy-induced apoptosis by modulating the Cx43 signaling pathway.

Impact of Intravenous Iron on Oxidative Stress and Mitochondrial Function in Experimental Chronic Kidney Disease

Background: Mitochondrial dysfunction is observed in chronic kidney disease (CKD). Iron deficiency anaemia (IDA), a common complication in CKD, is associated with poor clinical outcomes affecting mitochondrial function and exacerbating oxidative stress. Intravenous (iv) iron, that is used to treat anaemia, may lead to acute systemic oxidative stress. This study evaluated the impact of iv iron on mitochondrial function and oxidative stress. Methods: Uraemia was induced surgically in male Sprague-Dawley rats and studies were carried out 12 weeks later in two groups sham operated and uraemic (5/6 nephrectomy) rats not exposed to i.v. iron versus sham operated and uraemic rats with iv iron. Results: Induction of uraemia resulted in reduced iron availability (serum iron: 31.1 ± 1.8 versus 46.4 ± 1.4 µM), low total iron binding capacity (26.4 ± 0.7 versus 29.5 ± 0.8 µM), anaemia (haematocrit: 42.5 ± 3.0 versus 55.0 ± 3.0%), cardiac hypertrophy, reduced systemic glutathione peroxidase activity (1.12 ± 0.11 versus 1.48 ± 0.12 U/mL), tissue oxidative stress (oxidised glutathione: 0.50 ± 0.03 versus 0.36 ± 0.04 nmol/mg of tissue), renal mitochondrial dysfunction (proton/electron leak: 61.8 ± 8.0 versus 22.7 ± 5.77) and complex I respiration (134.6 ± 31.4 versus 267.6 ± 26.4 pmol/min/µg). Iron therapy had no effect on renal function and cardiac hypertrophy but improved anaemia and systemic glutathione peroxidase (GPx) activity. There was increased renal iron content and complex II and complex IV dysfunction. Conclusion: Iron therapy improved iron deficiency anaemia in CKD without significant impact on renal function or oxidant status.

Dietary restriction regimens for fighting kidney disease: Insights from rodent studies

This review critically discusses the research findings on the effects of various dietary restriction regimens in rodent models of kidney disease. Long-term caloric restriction executed at both early and progressive stages of kidney disease was found to exert beneficial effects in rodents. Moreover, some studies have also demonstrated the efficacy of short-term caloric restriction in treating the kidney disease of variable aetiologies possibly by improving mitochondrial dysfunction, autophagy process and suppression of inflammation. However, the mechanisms underlying these short-term caloric restriction mediated protective effects in rodent models of kidney disease are not completely understood. Importantly, few available evidences have also suggested that carbohydrate restriction can exert beneficial effects in aging and experimentally induced renal injury models, but the mechanisms are not explored yet. Interestingly, the benefits of low protein diet in kidney disease models are extensively reported in literature. However, in most of these studies implementation of the low protein dietary regimen was found to associated with increased high carbohydrate and caloric intake (non-isocaloric). Thus, testing the effects of low protein diet under isocaloric conditions might further help to particularly understand the role of dietary protein content in pathology of kidney disease. Moreover, the direct evidences comparing the efficacy of various dietary restriction regimens in rodent models of kidney diseases are also scarce at present.

Inhibition of Mitochondrial Complex I Aggravates Folic Acid-Induced Acute Kidney Injury

Background: Some researches revealed that mitochondrial dysfunction is associated with various kidney injury. However, the role of mitochondrial dysfunction in the pathogenesis of acute kidney injury (AKI) still needs evidence. Methods: We evaluated the effect of mitochondrial complex I inhibitor rotenone on folic acid (FA)-induced AKI in mice. Results: Strikingly, the mice pretreated with rotenone at a dose of 200 ppm in food showed exacerbated kidney injury as shown by higher levels of blood urea nitrogen and creatinine compared with FA alone group. Meanwhile, both renal tubular injury score and the expression of renal tubular injury marker neutrophil gelatinase-associated lipocalin were further elevated in rotenone-pretreated mice, suggesting the deteriorated renal tubular injury. Moreover, the decrements of mitochondrial DNA copy number and the expressions of mitochondrial Cytochrome c oxidase subunit 1, mitochondrial NADH dehydrogenase subunit 1, and mitochondria-specific superoxide dismutase (SOD2) in the kidneys of FA-treated mice were further reduced in rotenone-pretreated mice, indicating the aggravated mitochondrial damage. In parallel with the SOD2 reduction, the oxidative stress markers of malondialdehyde and HO-1 displayed greater increment in AKI mice with rotenone pretreatment in line with the deteriorated apoptotic response and inflammation. Conclusion: Our results suggested that the inhibition of mitochondrial complex I activity aggravated renal tubular injury, mitochondrial damage, oxidative stress, cell apoptosis, and inflammation in FA-induced AKI.

Oxidative Stress and Renal Fibrosis: Mechanisms and Therapies

Oxidative stress results from the disruption of the redox system marked by a notable overproduction of reactive oxygen species. There are four major sources of reactive oxygen species, including NADPH oxidases, mitochondria, nitric oxide synthases, and xanthine oxidases. It is well known that renal abnormalities trigger the production of reactive oxygen species by diverse mechanisms under various pathologic stimuli, such as acute kidney injury, chronic kidney disease, nephrotic syndrome, and metabolic disturbances. Mutually, accumulating evidences have identified that oxidative stress plays an essential role in tubulointerstitial fibrosis by myofibroblast activation as well as in glomerulosclerosis by mesangial sclerosis, podocyte abnormality, and parietal epithelial cell injury. Given the involvement of oxidative stress in renal fibrosis, therapies targeting oxidative stress seem promising in renal fibrosis management. In this review, we sketch the updated knowledge of the mechanisms of oxidative stress generation during renal diseases, the pathogenic processes of oxidative stress elicited renal fibrosis and treatments targeting oxidative stress during tubulointerstitial fibrosis and glomerulosclerosis.

Upregulation of Mitochondrial Transcription Factor A Promotes the Repairment of Renal Tubular Epithelial Cells in Sepsis by Inhibiting Reactive Oxygen Species-Mediated Toll-Like Receptor 4/p38MAPK Signaling

BACKGROUND

Mitochondrial transcription factor A (TFAM) plays multiple pathophysiologic roles in mitochondrial DNA (mtDNA) maintenance. However, the role of TFAM in sepsis-induced acute kidney injury (AKI) remains largely unknown.

METHODS

Lipopolysaccharide (LPS) treatment of HK-2 cells mimics the in vitro model of AKI inflammation. pcDNA3.1 plasmid was used to construct pcDNA3.1-TFAM. sh-TFAM-543, sh-TFAM-717, sh-TFAM-765, sh-TFAM-904 and pcDNA3.1-TFAM were transfected into HK-2 cells using Lipofectamine 2000. MtDNA transcriptional levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay was performed to assess the cell viability. Changes in reactive oxygen species (ROS) and mitochondrial membrane potential in HK-2 cells were detected using the corresponding kits. Immunofluorescence experiment was used to investigate the displacement of TFAM. mRNA and protein expression levels of TFAM and its related genes were measured by qRT-PCR and western blot respectively. Mice in sepsis were administered cecal ligation and puncture surgery.

RESULTS

LPS treatment was a non-lethal influencing factor, leading to the upregulation of ROS levels and downregulation of mtDNA copy number and NADH dehydrogenase subunit-1 (ND1) expression, and caused damage to the mitochondria. As the LPS treatment time increased, TFAM was displaced from the periphery of the nucleus to cytoplasm. TFAM reduced ROS and P38MAPK levels by inhibiting toll-like receptor 4 (TLR4) expression, ultimately inhibiting inflammation and repairing mtDNA.

CONCLUSIONS

Our results indicate that TFAM repairs mtDNA by blocking the TLR4/ROS/P38MAPK signaling pathway in inflammatory cells, thereby repairing septic tubular epithelial cells, and TFAM may serve as a new target for sepsis therapy.

Pirfenidone prevents acute kidney injury in the rat

Background

Pirfenidone is an orally active drug used for the treatment of idiopathic pulmonary fibrosis to slow loss of lung function; it acts mainly through an antifibrotic effect but also possesses antioxidant and anti-inflammatory properties. We assessed the effect of prophylactic administration of pirfenidone on acute kidney injury due to bilateral renal ischemia.

Methods

Eighteen rats were included and divided in: 1) sham-operated rats (S), 2) rats underwent bilateral renal ischemia for 20 min (I/R), and 3) rats treated with pirfenidone 700 mg/kg/day 24 h before surgery and subjected to bilateral renal ischemia for 20 min (I/R + PFN). All the rats were euthanized and studied 24 h after renal reperfusion.

Results

As was expected, the I/R group exhibited a significant reduction in creatinine clearance, urinary output and renal blood flow, as well as extensive tubular injury. These alterations were associated with a significant decrease in urinary excretion of nitrites and nitrates (UNO₂/NO₃V). In the I/R + PFN group, recovery of renal function and UNO₂/NO₃V was observed, together with lesser histological signs of tubular injury compared to the I/R group.

Conclusions

This study shows that prophylactic administration of pirfenidone prevented acute kidney injury due to bilateral ischemia in the rat. Recovery of NO production appears to be one of the mechanism of pirfenidone renoprotective effect. Our findings suggest that pirfenidone is a promising drug to reduce renal injury induced by I/R.

Salvianolic Acid A Protects the Kidney against Oxidative Stress by Activating the Akt/GSK-3β/Nrf2 Signaling Pathway and Inhibiting the NF-κB Signaling Pathway in 5/6 Nephrectomized Rats

Salvianolic acid A (SAA) is a bioactive polyphenol extracted from Salviae miltiorrhizae Bunge, which possesses a variety of pharmacological activities. In our previous study, we have demonstrated that SAA effectively attenuates kidney injury and inflammation in an established animal model of 5/6 nephrectomized (5/6Nx) rats. However, there has been limited research regarding the antioxidative effects of SAA on chronic kidney disease (CKD). Here, we examined the antioxidative effects and underlying mechanisms of SAA in 5/6Nx rats. The rats were injected with SAA (2.5, 5, and 10 mg·kg⁻¹·d⁻¹, ip) for 28 days. Biochemical, flow cytometry, and Western blot analyses showed that SAA significantly increased the activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GPx), and catalase (CAT) and lowered the levels of malondialdehyde (MDA), reactive oxygen species (ROS), and NADPH oxidase 4 (NOX-4) in a dose-dependent manner in 5/6Nx rats and in H₂O₂-induced HK-2 cells in vitro. Moreover, SAA enhanced the activation of the protein kinase B/glycogen synthase kinase-3β/nuclear factor-erythroid-2-related factor 2 (Akt/GSK-3β/Nrf2) signaling pathway in a dose-dependent manner and subsequently increased the expression of heme oxygenase-1 (HO-1) in the kidney of 5/6Nx rats, which were consistent with those obtained in H₂O₂-induced HK-2 cells in vitro shown by Western blot analysis. Furthermore, SAA significantly increased the expression of intranuclear Nrf2 and HO-1 proteins compared to HK-2 cells stimulated by LPS on the one hand, which can be enhanced by QNZ to some extent; on the other hand, SAA significantly lowered the expression of p-NF-κB p65 and ICAM-1 proteins compared to HK-2 cells stimulated by H₂O₂, which can be abrogated by ML385 to some extent. In conclusion, our results demonstrated that SAA effectively protects the kidney against oxidative stress in 5/6Nx rats. One of the pivotal mechanisms for the protective effects of SAA on kidney injury was mainly related with its antioxidative roles by activating the Akt/GSK-3β/Nrf2 signaling pathway and inhibiting the NF-κB signaling pathway.

Mitochondrial Dysfunction in Aged Macrophages and Lung during Primary Streptococcus pneumoniae Infection is Improved with Pirfenidone

Pneumococcal infections remain a leading cause of death in older adults, with the most serious cases occurring in persons ≥65 years of age. There is an urgent need to investigate molecular pathways underlying these impairments and devise new therapeutics to modulate innate immunity. The goal of our current study is to understand the impact of chronological aging on mitochondrial function in response to Streptococcus pneumoniae, a causative agent of bacterial pneumonia. Using chronologically aged murine models, our findings demonstrate that decreased ATP production is associated with dysregulated mitochondrial complex expression, enhanced oxidative stress, diminished antioxidant responses, and decreased numbers of healthy mitochondria in aged adult macrophages and lung in response to S. pneumoniae. Pre-treatment of aged macrophages with pirfenidone, an anti-fibrotic drug with antioxidant and anti-inflammatory properties, improved mitochondrial function and decreased cellular oxidative stress responses. In vivo administration of pirfenidone decreased superoxide formation, increased healthy mitochondria number, improved ATP production, and decreased inflammatory cell recruitment and pulmonary oedema in aged mouse lung during infection. Taken together, our data shed light on the susceptibility of older persons to S. pneumoniae and provide a possible therapeutic to improve mitochondrial responses in this population.

MnTBAP treatment ameliorates aldosterone-induced renal injury by regulating mitochondrial dysfunction and NLRP3 inflammasome signalling

Aldosterone plays an important role in the pathogenesis of chronic kidney disease (CKD) by directly damaging renal tubular cells. However, the treatment against aldosterone-induced renal injury is still limited. The present study was performed to examine the protection role of MnTBAP in modulating aldosterone-induced renal tubular injury both in vitro and vivo. MtD is induced by aldosterone in HK-2 cells, as evidenced by decreased expression of mtDNA and reduced mitochondrial membrane potential (MMP), which was markedly ameliorated by treatment with MnTBAP. HK-2 cells treated with MnTBAP demonstrated a reduction in cell apoptosis and improvements in cell phenotypic alterations following aldosterone challenge. Treatment with MnTBAP also inhibited the activation of the NLRP3 inflammasome and subsequent release of pro-inflammatory cytokines, IL-1β and IL-18. In addition, MnTBAP treatment of aldosterone-infused mice significantly improved mitochondrial morphology and function, suppressed the activation of NLRP3 inflammasome, reduced renal tubular cell apoptosis, decreased phenotypic alterations, and ameliorated renal apoptosis. We conclude that MnTBAP treatment ameliorates aldosterone-induced renal injury through regulating MtD and NLRP3 inflammsome signalling axis.

Renoprotective effect of Zhenwu decoction against renal fibrosis by regulation of oxidative damage and energy metabolism disorder

Zhenwu decoction (ZWD) is a promising traditional Chinese prescription against renal fibrosis, while its underlying mechanism remains unclear. Rat model of renal fibrosis were established and divided into control group, model group, ZWD treatment group and enalapril maleate treatment group. Metabolic profiles on serum samples from each group were acquired by using ultra performance liquid chromatography coupled with quadrupole time-of-flight high-resolution mass spectrometry. Metabolomics combined with molecular biology were comparatively conducted on samples of various groups. Fifteen potential biomarkers were identified and these biomarkers are mainly phospholipids and fatty acids. The results showed renal fibrosis was associated with oxidative damage and energy metabolism disorder. The results of histopathology, biochemistry and metabolomics demonstrated that ZWD exhibited an efficient renoprotective effect by alleviating oxidative stress, increasing energy metabolism and regulating fibrotic cytokines. This study provided scientific support for the research and development of new drugs from traditional Chinese medicine.

Hypochlorite modified albumins promote cell death in the tubule interstitium in rats via mitochondrial damage in obstructive nephropathy and the protective effects of antioxidant peptides

A major feature of the injury sustained by the kidney during obstructive nephropathy is a profound induction of apoptosis in the tubular epithelium. In this study, we explored the central roles of mitochondria and the mechanism of the protective effect of the mitochondrial targeted peptides in tubular cell apoptosis and interstitial fibrosis during obstructive nephropathy. Unilateral ureter obstruction (UUO) was performed on rats, and the animals were randomly assigned to intravenous treatment with normal saline, rat serum albumin (RSA), or HOCl-rat serum albumin (HOCl-RSA) in the presence or absence of SS-31. A sham-operation control group was set up by left ureteral dissociation but not ligation. Compared with the control group, UUO animals displayed fibrotic abnormalities, accompanied by increased expression of collagen-I, fibronectin, α-SMA protein and mRNA in the renal interstitium. They also displayed oxidative stress, as evidenced by increased levels of HOCl-alb, TBARS, and mitochondrial reactive oxygen species (ROS) and a decrease in MnSOD activity in the renal homogenate. Damage to mitochondrial structure and functions was observed, as evidenced by a decrease in the mitochondrial membrane potential (MMP), ATP production, mtDNA copy number alterations and release of cytochrome C (cyto C) from the mitochondria to the cytoplasm. These changes were accompanied by activation of caspase-3, caspase-7, caspase-9, and PARP-1 and increased apoptotic cells in the proximal tubules. HOCl-RSA challenge further exacerbated the above biological effects in UUO animals, but these effects were prevented by administration of SS-31. These data suggested that accumulation of HOCl-alb may promote tubular cell apoptosis and interstitial fibrosis, probably related to mitochondrial oxidative stress and damage, and that SS-31 might contribute to apoptotic pathway suppression via scavenging of ROS in the mitochondria.

Rotenone ameliorates chronic renal injury caused by acute ischemia/reperfusion

Acute kidney injury (AKI) has been widely recognized as an important risk factor leading to the occurrence and progression of chronic kidney disease (CKD). Thus, development of the strategies in retarding the transition of AKI to CKD is becoming a hot research field. Recently, accumulating evidence suggested a pathogenic role of mitochondrial dysfunction in both AKI and CKD. Therefore, in the present study, we evaluated the effect of mitochondrial complex 1 inhibition by rotenone on the chronic renal damage induced by acute ischemia-reperfusion. The mice were treated with 45 min unilateral renal ischemia and reperfusion (I/R) to induce an acute renal injury. After three days of I/R injury, rotenone at a dose of 200 ppm in food was administered to the mice. Strikingly, after three weeks treatment with rotenone, we found that the unilateral I/R-induced tubular damage, tubulointerstitial fibrosis were all attenuated by rotenone as determined by the tubular injury score, Masson staining, and the levels of collagen-I, collagen-III, fibronectin, PAI-1, and TGF-β. Meanwhile, the enhanced inflammatory markers of TNF-α, IL-1β, IL-6, and IL-18 and apoptotic markers of Bax and caspase-3 were all significantly blunted by inhibiting mitochondrial complex-1. Moreover, rotenone treatment also partially protected the mitochondria as shown by the restoration of mitochondrial SOD (SOD2), ATPB, and mitochondrial DNA copy number. These findings suggested that inhibition of mitochondrial complex-1 activity by rotenone could retard the progression of AKI to CKD probably via protecting the mitochondrial function to some extent.

Renal hypoxia in kidney disease: Cause or consequence?

Tissue hypoxia has been proposed as an important factor in the pathophysiology of both chronic kidney disease (CKD) and acute kidney injury (AKI), initiating and propagating a vicious cycle of tubular injury, vascular rarefaction, and fibrosis and thus exacerbation of hypoxia. Here, we critically evaluate this proposition by systematically reviewing the literature relevant to the following six questions: (i) Is kidney disease always associated with tissue hypoxia? (ii) Does tissue hypoxia drive signalling cascades that lead to tissue damage and dysfunction? (iii) Does tissue hypoxia per se lead to kidney disease? (iv) Does tissue hypoxia precede pathology? (v) Does tissue hypoxia colocalize with pathology? (vi) Does prevention of tissue hypoxia prevent kidney disease? We conclude that tissue hypoxia is a common feature of both AKI and CKD. Furthermore, at least under in vitro conditions, renal tissue hypoxia drives signalling cascades that lead to tissue damage and dysfunction. Tissue hypoxia itself can lead to renal pathology, independent of other known risk factors for kidney disease. There is also some evidence that tissue hypoxia precedes renal pathology, at least in some forms of kidney disease. However, we have made relatively little progress in determining the spatial relationships between tissue hypoxia and pathological processes (i.e. colocalization) or whether therapies targeted to reduce tissue hypoxia can prevent or delay the progression of renal disease. Thus, the hypothesis that tissue hypoxia is a "common pathway" to both AKI and CKD still remains to be adequately tested.

Mito-TEMPO Alleviates Renal Fibrosis by Reducing Inflammation, Mitochondrial Dysfunction, and Endoplasmic Reticulum Stress

Background

Renal fibrosis is a common pathological symptom of chronic kidney disease (CKD). Many studies support that mitochondrial dysfunction and endoplasmic reticulum (ER) stress are implicated in the pathogenesis of CKD. In our study, we investigated the benefits and underlying mechanisms of Mito-TEMPO on renal fibrosis in 5/6 nephrectomy mice.

Methods

Mice were randomly divided into five groups as follows: control group, CKD group, CKD + Mito-TEMPO (1 mg·kg^-1·day^-1) group, CKD + Mito-TEMPO (3 mg·kg^-1·day^-1) group, and Mito-TEMPO group (3 mg·kg^-1·day^-1). Renal fibrosis was evaluated by PAS, Masson staining, immunohistochemistry, and real-time PCR. Oxidative stress markers such as SOD2 activity and MDA level in serum and isolated mitochondria from renal tissue were measured by assay kits. Mitochondrial superoxide production was evaluated by MitoSOX staining and Western blot. Mitochondrial dysfunction was assessed by electron microscopy and real-time PCR. ER stress-associated protein was measured by Western blot.

Results

Impaired renal function and renal fibrosis were significantly improved by Mito-TEMPO treatment. Furthermore, inflammation cytokines, profibrotic factors, oxidative stress markers, mitochondrial dysfunction, and ER stress were all increased in the CKD group. However, these effects were significantly ameliorated in the Mito-TEMPO treatment group.

Conclusions

Mito-TEMPO ameliorates renal fibrosis by alleviating mitochondrial dysfunction and endoplasmic reticulum stress possibly through the Sirt3-SOD2 pathway, which sheds new light on prevention of renal fibrosis in chronic kidney disease.

Cytosolic carnitine acetyltransferase as a source of cytosolic acetyl-CoA: a possible mechanism for regulation of cardiac energy metabolism

The role of carnitine acetyltransferase (CrAT) in regulating cardiac energy metabolism is poorly understood. CrAT modulates mitochondrial acetyl-CoA/CoA (coenzyme A) ratios, thus regulating pyruvate dehydrogenase activity and glucose oxidation. Here, we propose that cardiac CrAT also provides cytosolic acetyl-CoA for the production of malonyl-CoA, a potent inhibitor of fatty acid oxidation. We show that in the murine cardiomyocyte cytosol, reverse CrAT activity (RCrAT, producing acetyl-CoA) is higher compared with the liver, which primarily uses ATP-citrate lyase to produce cytosolic acetyl-CoA for lipogenesis. The heart displayed a lower RCrAT K_m for CoA compared with the liver. Furthermore, cytosolic RCrAT accounted for 4.6 ± 0.7% of total activity in heart tissue and 12.7 ± 0.2% in H9C2 cells, while highly purified heart cytosolic fractions showed significant CrAT protein levels. To investigate the relationship between CrAT and acetyl-CoA carboxylase (ACC), the cytosolic enzyme catalyzing malonyl-CoA production from acetyl-CoA, we studied ACC2-knockout mouse hearts which showed decreased CrAT protein levels and activity, associated with increased palmitate oxidation and acetyl-CoA/CoA ratio compared with controls. Conversely, feeding mice a high-fat diet for 10 weeks increased cardiac CrAT protein levels and activity, associated with a reduced acetyl-CoA/CoA ratio and glucose oxidation. These data support the presence of a cytosolic CrAT with a low K_m for CoA, favoring the formation of cytosolic acetyl-CoA, providing an additional source to the classical ATP-citrate lyase pathway, and that there is an inverse relation between CrAT and the ratio of acetyl-CoA/CoA as evident in conditions affecting the regulation of cardiac energy metabolism.

Extracellular Mitochondrial DNA Is Generated by Fibroblasts and Predicts Death in Idiopathic Pulmonary Fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) involves the accumulation of α-smooth muscle actin-expressing myofibroblasts arising from interactions with soluble mediators such as transforming growth factor-β1 (TGF-β1) and mechanical influences such as local tissue stiffness. Whereas IPF fibroblasts are enriched for aerobic glycolysis and innate immune receptor activation, innate immune ligands related to mitochondrial injury, such as extracellular mitochondrial DNA (mtDNA), have not been identified in IPF.

OBJECTIVES

We aimed to define an association between mtDNA and fibroblast responses in IPF.

METHODS

We evaluated the response of normal human lung fibroblasts (NHLFs) to stimulation with mtDNA and determined whether the glycolytic reprogramming that occurs in response to TGF-β1 stimulation and direct contact with stiff substrates, and spontaneously in IPF fibroblasts, is associated with excessive levels of mtDNA. We measured mtDNA concentrations in bronchoalveolar lavage (BAL) from subjects with and without IPF, as well as in plasma samples from two longitudinal IPF cohorts and demographically matched control subjects.

MEASUREMENTS AND MAIN RESULTS

Exposure to mtDNA augments α-smooth muscle actin expression in NHLFs. The metabolic changes in NHLFs that are induced by interactions with TGF-β1 or stiff hydrogels are accompanied by the accumulation of extracellular mtDNA. These findings replicate the spontaneous phenotype of IPF fibroblasts. mtDNA concentrations are increased in IPF BAL and plasma, and in the latter compartment, they display robust associations with disease progression and reduced event-free survival.

CONCLUSIONS

These findings demonstrate a previously unrecognized and highly novel connection between metabolic reprogramming, mtDNA, fibroblast activation, and clinical outcomes that provides new insight into IPF.

Pirfenidone inhibits myofibroblast differentiation and lung fibrosis development during insufficient mitophagy

Background

Pirfenidone (PFD) is an anti-fibrotic agent used to treat idiopathic pulmonary fibrosis (IPF), but its precise mechanism of action remains elusive. Accumulation of profibrotic myofibroblasts is a crucial process for fibrotic remodeling in IPF. Recent findings show participation of autophagy/mitophagy, part of the lysosomal degradation machinery, in IPF pathogenesis. Mitophagy has been implicated in myofibroblast differentiation through regulating mitochondrial reactive oxygen species (ROS)-mediated platelet-derived growth factor receptor (PDGFR) activation. In this study, the effect of PFD on autophagy/mitophagy activation in lung fibroblasts (LF) was evaluated, specifically the anti-fibrotic property of PFD for modulation of myofibroblast differentiation during insufficient mitophagy.

Methods

Transforming growth factor-β (TGF-β)-induced or ATG5, ATG7, and PARK2 knockdown-mediated myofibroblast differentiation in LF were used for in vitro models. The anti-fibrotic role of PFD was examined in a bleomycin (BLM)-induced lung fibrosis model using PARK2 knockout (KO) mice.

Results

We found that PFD induced autophagy/mitophagy activation via enhanced PARK2 expression, which was partly involved in the inhibition of myofibroblast differentiation in the presence of TGF-β. PFD inhibited the myofibroblast differentiation induced by PARK2 knockdown by reducing mitochondrial ROS and PDGFR-PI3K-Akt activation. BLM-treated PARK2 KO mice demonstrated augmentation of lung fibrosis and oxidative modifications compared to those of BLM-treated wild type mice, which were efficiently attenuated by PFD.

Conclusions

These results suggest that PFD induces PARK2-mediated mitophagy and also inhibits lung fibrosis development in the setting of insufficient mitophagy, which may at least partly explain the anti-fibrotic mechanisms of PFD for IPF treatment.

Resveratrol improves mitochondrial function in the remnant kidney from 5/6 nephrectomized rats

Mitochondrial dysfunction is involved in the pathogenesis of chronic kidney disease (CKD). Resveratrol has been demonstrated to be beneficial for the recovery of kidney diseases. In this study, the 5/6 nephrectomized rat was used as a CKD model and the TGF-β1-exposed mouse mesangial cells were used as an in vitro model. Pathological examination showed that resveratrol treatment attenuated glomerular injury in the remnant kidney of 5/6 nephrectomized rat. Additionally, resveratrol improved mitochondrial function in vivo and in vitro, as evidenced by increasing mitochondrial membrane potential, increasing ATP, decreasing reactive oxygen species production and enhancing activities of complex I and III. Furthermore, the dysregulated expressions of electron transport chain proteins and fission/fusion proteins in the kidney of 5/6 nephrectomize rats and TGF-β1-exposed mesangial cells were restored by resveratrol. Finally, upregulated sirt1 and PGC-1α deacetylation were found after treatment with resveratrol in vivo and in vitro, which may contribute to the mitochondrial protective effects of resveratrol. The results demonstrate that resveratrol protects the mitochondria of kidney in 5/6 nephrectomized rats and TGF-β1 induced mesangial cells. The study provides new insights into the renoprotective mechanisms of resveratrol.

Role of mitochondrial dysfunction in renal fibrosis promoted by hypochlorite-modified albumin in a remnant kidney model and protective effects of antioxidant peptide SS-31

Oxidative stress aggravates renal fibrosis, a pathway involved in almost all forms of chronic kidney disease (CKD). However, the underlying mechanism involved in the pathogenesis of renal oxidative stress has not been completely elucidated. In this study, we explored the role and mechanism of hypochlorite-modified albumin (HOCl-alb) in mediating oxidative stress and fibrotic response in a remnant-kidney rat model. Five-sixths nephrectomy (5/6 NX) was performed on the rats and then the animals were randomly assigned to intravenous treatment with either vehicle alone, or HOCl-rat serum albumin (RSA) in the presence or absence of SS-31 (administered intraperitoneally). A sham-operation control group was set up concurrently. Compared with the control group, 5/6 NX animals displayed marked mitochondrial (mt) dysfunction, as evidenced by decrease of mitochondrial membrane potential (MMP), ATP production, mtDNA copy number alterations and manganese superoxide dismutase (MnSOD) activity, release of cytochrome C (Cyto C) from mitochondria to the cytoplasm, and increase of mitochondrial reactive oxygen species in renal tissues. They also displayed increased levels of HOCl-alb in both plasma and renal tissues. These changes were accompanied by accumulation of extracellular matrix, worsened proteinuria, deteriorated renal function, and a marked increase of macrophage infiltration along with up-regulation of monocyte chemoattractant protein (MCP)-1 and transforming growth factor (TGF)-β1 expression. HOCl-alb challenge further exacerbated the above biological effects in 5/6 NX animals, but these adverse effects were prevented by administration of SS-31, a mitochondrial targeted antioxidant peptide. These data suggest that accumulation of HOCl-alb may promote renal inflammation and fibrosis, probably related to mitochondrial oxidative stress and dysfunction and that the mitochondrial targeted peptide SS-31 might be a novel therapy for renal fibrosis and chronic renal failure (CRF).

NLRP3 Deficiency Attenuates Renal Fibrosis and Ameliorates Mitochondrial Dysfunction in a Mouse Unilateral Ureteral Obstruction Model of Chronic Kidney Disease

Background and Aims. The nucleotide-binding domain and leucine-rich repeat containing PYD-3 (NLRP3) inflammasome has been implicated in the pathogenesis of chronic kidney disease (CKD); however, its exact role in glomerular injury and tubulointerstitial fibrosis is still undefined. The present study was performed to identify the function of NLRP3 in modulating renal injury and fibrosis and the potential involvement of mitochondrial dysfunction in the murine unilateral ureteral obstruction (UUO) model of CKD. Methods. Employing wild-type (WT) and NLRP3^−/− mice with or without UUO, we evaluated renal structure, tissue injury, and mitochondrial ultrastructure, as well as expression of some vital molecules involved in the progression of fibrosis, apoptosis, inflammation, and mitochondrial dysfunction. Results. The severe glomerular injury and tubulointerstitial fibrosis induced in WT mice by UUO was markedly attenuated in NLRP3^−/− mice as evidenced by blockade of extracellular matrix deposition, decreased cell apoptosis, and phenotypic alterations. Moreover, NLRP3 deletion reversed UUO-induced impairment of mitochondrial morphology and function. Conclusions. NLRP3 deletion ameliorates mitochondrial dysfunction and alleviates renal fibrosis in a murine UUO model of CKD.

Mass Spectrometry Imaging of Kidney Tissue Sections of Rat Subjected to Unilateral Ureteral Obstruction

Chronic kidney disease (CKD) poses a serious threat to the quality of human life and health with an increasing incidence worldwide. Renal fibrosis is closely related to CKD and regarded as the final common pathophysiological pathway in most cases of end-stage renal diseases. Elucidating the mechanisms underlying renal fibrosis and developing novel therapeutic strategies are of great importance. Herein, matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) based on 1, 5-diaminonaphthalene hydrochloride was applied to the rat model of unilateral ureteral obstruction (UUO) to investigate metabolic changes during renal fibrosis. Among identified endogenous compounds, twenty-one metabolites involved in metabolic networks such as glycolysis, tricarboxylic acid (TCA) cycle, ATP metabolism, fatty acids metabolism, antioxidants, and metal ions underwent relatively obvious changes after 1 and 3 weeks of UUO. Unique distribution of the metabolites was obtained, and metabolic changes of kidneys during renal fibrosis were investigated simultaneously for the first time. These findings once again highlighted the promising potential of the organic salt matrix for application in small molecule in situ MSI and in the field of biomedical research.

Preparation of novel pirfenidone microspheres for lung-targeted delivery: in vitro and in vivo study

The aim of this study was to develop and characterize pirfenidone (PF)-loaded chitosan microspheres for lung targeting. The microspheres were prepared using the emulsion-solvent evaporation method and characterized by assessing morphology, particle size, and zeta potential. The microspheres had a spherical nature with highly smooth and integrated surfaces. The particle size of microspheres was 4.6±0.3 µm, and the zeta potential was 20.3±1.4 mV. The in vitro release results indicated that the obtained formulation of PF could reach the state of sustained release with a biphasic drug release pattern. It was observed that there was no significant difference in both the percentage of entrapment efficiency and that of drug release before and after the stability study. In vivo, the calculated relative bioavailability indicated greater pulmonary absorption of PF when it was encapsulated in microspheres. According to histopathological studies, no histological change occurred to the rat lung after the administration of PF-loaded chitosan microspheres.

Inhibition of mitochondrial complex-1 restores the downregulation of aquaporins in obstructive nephropathy

Obstructive kidney disease is a common complication in the clinic. Downregulation of aquaporins (AQPs) in obstructed kidneys has been thought as a key factor leading to the polyuria and impairment of urine-concentrating capability after the release of kidney obstruction. The present study was to investigate the role of mitochondrial complex-1 in modulating AQPs in obstructive nephropathy. Following 7-day unilateral ureteral obstruction (UUO), AQP1, AQP2, AQP3, and vasopressin 2 (V₂) receptor were remarkably reduced as determined by qRT-PCR and/or Western blotting. Notably, inhibition of mitochondrial complex-1 by rotenone markedly reversed the downregulation of AQP1, AQP2, AQP3, and V₂ In contrast, AQP4 was not affected by kidney obstruction or rotenone treatment. In a separate study, rotenone also attenuated AQPs' downregulation after 48-h UUO. To study the potential mechanisms in mediating the rotenone effects on AQPs, we examined the regulation of the COX-2/microsomal prostaglandin E synthase (mPGES)-1/PGE₂/EP pathway and found that COX-2, mPGES-1, and renal PGE₂ content were all significantly elevated in obstructive kidneys, which was not affected by rotenone treatment. For EP receptors, EP₂ and EP₄ but not EP₁ and EP₃ were upregulated in obstructive kidneys. Importantly, rotenone strikingly suppressed EP₁ and EP₄ but not EP₂ and EP₃ receptors. However, treatment of EP₁ antagonist SC-51322 could not affect AQPs' reduction in obstructed kidneys. Collectively, these findings suggested an important role of mitochondrial dysfunction in modulating AQPs and V₂ receptor in obstructive nephropathy possibly via prostaglandin-independent mechanisms.

New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease

In chronic kidney disease inflammatory processes and stimulation of immune cells result in overproduction of free radicals. In combination with a reduced antioxidant capacity this causes oxidative stress. This review focuses on current pathogenic concepts of oxidative stress for the decline of kidney function and development of cardiovascular complications. We discuss the impact of mitochondrial alterations and dysfunction, a pathogenic role for hyperuricemia, and disturbances of vitamin D metabolism and signal transduction. Recent antioxidant therapy options including the use of vitamin D and pharmacologic therapies for hyperuricemia are discussed. Finally, we review some new therapy options in diabetic nephropathy including antidiabetic agents (noninsulin dependent), plant antioxidants, and food components as alternative antioxidant therapies.

Human biliverdin reductase promotes EMT through the ERK1/2 signal pathway in breast cancer

Epithelial-to-mesenchymal transition (EMT) plays an important role in the development of the invasive and metastatic potentials of breast cancer cells during progression. Human biliverdin reductase (hBVR), an enzyme in the heme metabolism pathway, is involved in hypoxia-induced renal tubular EMT. However, whether hBVR contributes to the EMT of breast cancer remains unclear. Here, we used breast cancer cell lines (MCF-7, T-47D) and normal breast epithelial cells (MCF-10A) to explore the potential role of hBVR in the EMT of breast cancer. Western blot, RT-PCR and immunofluorescence were employed to test the expression and location of hBVR in the cell lines. Small interfering RNA of hBVR (si-hBVR) was used to knockdown the expression of hBVR, and U0126 was applied to inhibit the ERK1/2 signaling in MCF-7, T-47D cells. We found that hBVR highly expressed in MCF-7 and T-47D cells compared with MCF-10A cells, and had different cellular locations between them. Our results revealed that EMT occurred in tissues from breast cancer patients and breast cancer cell lines. However, the EMT in MCF-7 and T-47D cells was suppressed by si-hBVR and U0126. Furthermore, the expression of phosphorylated ERK1/2 was down-regulated by si-hBVR. In addition, hBVR regulated EMT through the ERK1/2 signaling, but bilirubin, which is a product of hBVR in the heme metabolism pathway in breast cancer, did not. Taken together, these findings provide new evidence that hBVR plays an important role in promoting EMT in human breast cancer through the ERK1/2 signaling pathway, and hBVR may be a therapeutic target for this disease.

Mesenchymal Stem Cells Synergize with 635, 532, and 405 nm Laser Wavelengths in Renal Fibrosis: A Pilot Study

OBJECTIVE

To address whether a single treatment of one of three visible light wavelengths, 635, 532, and 405 nm (constant wave, energy density 2.9 J/m²), could affect the hallmarks of established renal fibrosis and whether these wavelengths could facilitate mesenchymal stem cell (MSC) beneficence.

BACKGROUND DATA

Chronic kidney disease is a global health problem with only 20% receiving care worldwide. Kidneys with compromised function have ongoing inflammation, including increased oxidative stress and apoptosis, peritubular capillary loss, tubular atrophy, and tubulointerstitial fibrosis. Promising studies have highlighted the significant potential of MSC-based strategies to mitigate fibrosis; however, reversal of established fibrosis has been problematic, suggesting that methods to potentiate MSC effects require further development. Laser treatments at visible wavelengths have been reported to enhance mitochondrial potential and available cellular ATP, facilitate proliferation, and inhibit apoptosis. We hypothesized that laser-delivered energy might provide wavelength-specific effects in the fibrotic kidney and enhance MSC responses.

MATERIALS AND METHODS

Renal fibrosis, established in C57BL6 mice following 21 days of unilateral ureter obstruction (UUO), was treated with one of three wavelengths alone or with autologous MSC. Mitochondrial activity, cell proliferation, apoptosis, and cytokines were measured 24 h later.

RESULTS

Wavelengths 405, 532, and 635 nm all significantly synergized with MSC to enhance mitochondrial activity and reduce apoptosis. Proliferative activity was observed in the renal cortices following combined treatment with the 532 nm laser and MSC; endothelial proliferation increased in response to the 635 nm laser alone and to the combined effects of MSC and the 405 nm wavelength. Reductions of transforming growth factor-β were observed with 532 nm alone and when combined with MSC.

CONCLUSIONS

Specific wavelengths of laser energy appear to induce different responses in renal fibrotic tissue. These findings support further study in the development of a customized laser therapy program of combined wavelengths to optimize MSC effects in the treatment of renal fibrosis.

NLRP3 deletion protects against renal fibrosis and attenuates mitochondrial abnormality in mouse with 5/6 nephrectomy

Progressive fibrosis in chronic kidney disease (CKD) is the well-recognized cause leading to the progressive loss of renal function. Emerging evidence indicated a pathogenic role of the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome in mediating kidney injury. However, the role of NLRP3 in the remnant kidney disease model is still undefined. The present study was undertaken to evaluate the function of NLRP3 in modulating renal fibrosis in a CKD model of 5/6 nephrectomy (5/6 Nx) and the potential involvement of mitochondrial dysfunction in the pathogenesis. Employing NLRP3+/+ and NLRP3−/− mice with or without 5/6 Nx, we examined renal fibrotic response and mitochondrial function. Strikingly, tubulointerstitial fibrosis was remarkably attenuated in NLRP3−/− mice as evidenced by the blockade of extracellular matrix deposition. Meanwhile, renal tubular cells in NLRP3−/− mice maintained better mitochondrial morphology and higher mitochondrial DNA copy number, indicating an amelioration of mitochondrial abnormality. Moreover, NLRP3 deletion also blunted the severity of proteinuria and CKD-related hypertension. To further evaluate the direct role of NLRP3 in triggering fibrogenesis, mouse proximal tubular cells (PTCs) were subjected to transforming growth factor β1 (TGF-β1), and the cellular phenotypic changes were detected. As expected, TGF-β1-induced alterations of PTC phenotype were abolished by NLRP3 small interfering RNA, in line with a protection of mitochondrial function. Taken together, NLRP3 deletion protected against renal fibrosis in the 5/6 Nx disease model, possibly via inhibiting mitochondrial dysfunction.

The decreased expression of electron transfer flavoprotein β is associated with tubular cell apoptosis in diabetic nephropathy

Tubular injury is closely correlated with the development of progressive diabetic nephropathy (DN), particularly in cases of type 2 diabetes. The apoptosis of tubular cells has been recognized as a major cause of tubular atrophy, followed by tubulointerstitial fibrosis. Electron transfer flavoprotein β (ETFβ) is known as an important electron acceptor in energy metabolism, but its role in DN was not fully understood. In the present study, we examined the expression pattern of ETFβ using diabetic kidney samples and further investigated ETFβ involvement in tubular epithelial cell (TEC) apoptosis. Human renal biopsy specimens from patients with DN as well as a spontaneous rat model of diabetes using Otsuka Long-Evans Tokushima fatty (OLETF) rats, were employed in order to examine the expression of ETFβ and cell apoptosis in kidneys during the development of DN (for the rats, at 36 and 56 weeks of age respectively). Moreover, ETFβ siRNA was used to investigate the role of ETFβ in the apoptosis of renal tubular cells. Our present results showed that the expression of ETFβ in the kidneys was progressively decreased both in patients with DN and OLETF rats, which coincided with progressive renal injury and TEC apoptosis. In addition, the in vitro study demonstrated that knockdown of ETFβ caused apoptosis in tubular cells, as proven by the increased expression of pro-apoptotic proteins and TUNEL assay. Therefore, the findings of our present study suggest that ETFβ plays an important role in renal tubular cell apoptosis during the progression of DN.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

Emerging Agents for the Management of Nephrotic Syndrome: Progress to Date

Nephrotic Syndrome is a rare condition associated with high morbidity in the 20-40% of children and adolescents who fail to respond to standard immunosuppressive therapies. Novel non-immunologic mechanisms of widely used immunosuppressive therapies, as well as emerging anti-inflammatory drugs, and anti-fibrotics may play a crucial role in the treatment of patients with refractory disease. This article will review some of these treatments and their various stages of investigation.

TGF-β/BMP proteins as therapeutic targets in renal fibrosis. Where have we arrived after 25 years of trials and tribulations?

The understanding of renal fibrosis in chronic kidney disease (CKD) remains as a challenge. More than 10% of the population of developed countries suffer from CKD. Proliferation and activation of myofibroblasts and accumulation of extracellular matrix proteins are the main features of kidney fibrosis, a process in which a large number of cytokines are involved. Targeting cytokines responsible for kidney fibrosis development might be an important strategy to face the problem of CKD. The increasing knowledge of the signaling pathway network of the transforming growth factor beta (TGF-β) superfamily members, such as the profibrotic cytokine TGF-β1 or the bone morphogenetic proteins (BMPs), and their involvement in the regulation of kidney fibrosis, has stimulated numerous research teams to look for potential strategies to inhibit profibrotic cytokines or to enhance the anti-fibrotic actions of other cytokines. The consequence of all these studies is a better understanding of all these canonical (Smad-mediated) and non-canonical signaling pathways. In addition, the different receptors involved for signaling of each cytokine, the different combinations of type I-type II receptors, and the presence and function of co-receptors that can influence the biological response have been also described. However, are these studies leading to suitable strategies to block the appearance and progression of kidney fibrosis? In this review, we offer a critical perspective analyzing the achievements using the most important strategies developed up till now: TGF-β antibodies, chemical inhibitors of TGF-β receptors, miRNAs and signaling pathways and BMP agonists with a potential role as therapeutic molecules against kidney fibrosis.

Role and New Insights of Pirfenidone in Fibrotic Diseases

Pirfenidone (PFD) is a non-peptide synthetic molecule issued as a broad-spectrum anti-fibrotic drug with the ability to decrease TGF-β1, TNF-α, PDGF and COL1A1 expression, which is highly related to prevent or remove excessive deposition of scar tissue in several organs. Basic and clinical evidence suggests that PFD may safely slow or inhibit the progressive fibrosis swelling after tissue injuries. Furthermore, a number of evidence suggests that this molecule will have positive effects in the treatment of other inflammatory diseases. This review contains current research in which PFD has been used as the treatment of several diseases, and focus mainly in the outcomes related to improve inflammation and fibrogenesis. Therefore, the main goal of this review is to focus on the novel findings of PFD efficacy rather than deepen in the chemical aspects of the molecule.