Low-dose hydralazine prevents fibrosis in a murine model of acute kidney injury-to-chronic kidney disease progression

Krüppel-like factor 4 modulates the miR-101/COL10A1 axis to inhibit renal fibrosis after AKI by regulating epithelial-mesenchymal transition

Acute kidney injury (AKI) can progress to renal fibrosis and chronic kidney disease (CKD), which reduces quality of life and increases the economic burden on patients. However, the molecular mechanisms underlying renal fibrosis following AKI remain unclear. This study tested the hypothesis that the Krüppel-like factor 4 (KLF4)/miR-101/Collagen alpha-1X (COL10A1) axis could inhibit epithelial-mesenchymal transition (EMT) and renal fibrosis after AKI in a mouse model of ischemia-reperfusion (I/R)-induced renal fibrosis and HK-2 cells by gene silencing, overexpression, immunofluorescence, immunohistochemistry, real-time quantitative PCR, Western blotting, dual-luciferase reporter assay, fluorescence in situ hybridization (FISH) and ELISA. Compared with the Sham group, I/R induced renal tubular and glomerular injury and fibrosis, and increased the levels of BUN, serum Scr and neutrophil gelatinase-associated lipocalin (NGAL), Col10a1 and Vimentin expression, but decreased E-cadherin expression in the kidney tissues of mice at 42 days post-I/R. Similarly, hypoxia promoted fibroblastic morphological changes in HK-2 cells and enhanced NGAL, COL10A1, Vimentin, and α-SMA expression, but reduced E-cadherin expression in HK-2 cells. These pathological changes were significantly mitigated in COL10A1-silenced renal tissues and HK-2 cells. KLF4 induces miR-101 transcription. More importantly, hypoxia upregulated Vimentin and COL10A1 expression, but decreased miR-101, KLF4, and E-cadherin expression in HK-2 cells. These hypoxic effects were significantly mitigated or abrogated by KLF4 over-expression in the HK-2 cells. Our data indicate that KLF4 up-regulates miR-101 expression, leading to the downregulation of COL10A1 expression, inhibition of EMT and renal fibrosis during the pathogenic process of I/R-related renal fibrosis.

Understanding the role of ten-eleven translocation family proteins in kidney diseases

Epigenetic mechanisms play a critical role in the pathogenesis of human diseases including kidney disorders. As the erasers of DNA methylation, Ten-eleven translocation (TET) family proteins can oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), thus leading to passive or active DNA demethylation. Similarly, TET family proteins can also catalyze the same reaction on RNA. In addition, TET family proteins can also regulate chromatin structure and gene expression in a catalytic activity-independent manner through recruiting the SIN3A/HDAC co-repressor complex. In 2012, we reported for the first time that the genomic 5-hydroxymethylcytosine level and the mRNA levels of Tet1 and Tet2 were significantly downregulated in murine kidneys upon ischemia and reperfusion injury. Since then, accumulating evidences have eventually established an indispensable role of TET family proteins in not only acute kidney injury but also chronic kidney disease. In this review, we summarize the upstream regulatory mechanisms and the pathophysiological role of TET family proteins in major types of kidney diseases and discuss their potential values in clinical diagnosis and treatment.

RAS protein activator-like 2 (RASAL2) initiates peritubular capillary rarefaction in hypoxic renal interstitial fibrosis

The progression of chronic kidney disease (CKD) often involves renal interstitial fibrosis (RIF) and subsequent loss of peritubular capillaries (PTCs), which enhances disease severity. Despite advancements in our understanding of fibrosis, effective interventions for reversing capillary loss remain elusive. Notably, RIF exhibits reduced capillary density, whereas renal cell carcinoma (RCC) shows robust angiogenesis under hypoxic conditions. Using RNA sequencing and bioinformatics, we identified differentially expressed genes (DEGs) in hypoxic human renal tubular epithelial cells (HK-2) and renal cancer cells (786-0). Analysis of altered Ras and PI3K/Akt pathways coupled with hub gene investigation revealed RAS protein activator-like 2 (RASAL2) as a key candidate. Subsequent in vitro and in vivo studies confirmed RASAL2's early-stage response in RIF, which reduced with fibrosis progression. RASAL2 suppression in HK-2 cells enhanced angiogenesis, as evidenced by increased proliferation, migration, and branching of human umbilical vein endothelial cells (HUVECs) co-cultured with HK-2 cells. In mice, RASAL2 knockdown improved Vascular endothelial growth factor A (VEGFA) and Proliferating cell nuclear antigen (PCNA) levels in unilateral ureteral occlusion (UUO)-induced fibrosis (compared to wild type). Hypoxia-inducible factor 1 alpha (HIF-1α) emerged as a pivotal mediator, substantiated by chromatin immunoprecipitation (ChIP) sequencing, with its induction linked to activation. Hypoxia increased the production of RASAL2-enriched extracellular vesicles (EVs) derived from tubular cells, which were internalized by endothelial cells, contributing to the exacerbation of PTC loss. These findings underscore RASAL2's role in mediating reduced angiogenesis in RIF and reveal a novel EV-mediated communication between hypoxic tubular- and endothelial cells, demonstrating a complex interplay between angiogenesis and fibrosis in CKD pathogenesis.

Nucleic acid and protein methylation modification in renal diseases

Although great efforts have been made to elucidate the pathological mechanisms of renal diseases and potential prevention and treatment targets that would allow us to retard kidney disease progression, we still lack specific and effective management methods. Epigenetic mechanisms are able to alter gene expression without requiring DNA mutations. Accumulating evidence suggests the critical roles of epigenetic events and processes in a variety of renal diseases, involving functionally relevant alterations in DNA methylation, histone methylation, RNA methylation, and expression of various non-coding RNAs. In this review, we highlight recent advances in the impact of methylation events (especially RNA m6A methylation, DNA methylation, and histone methylation) on renal disease progression, and their impact on treatments of renal diseases. We believe that a better understanding of methylation modification changes in kidneys may contribute to the development of novel strategies for the prevention and management of renal diseases.

HIF-1α: A potential therapeutic opportunity in renal fibrosis

Renal fibrosis is a common outcome of various renal injuries, leading to structural destruction and functional decline of the kidney, and is also a critical prognostic indicator and determinant in renal diseases therapy. Hypoxia is induced in different stress and injuries in kidney, and the hypoxia inducible factors (HIFs) are activated in the context of hypoxia in response and regulation the hypoxia in time. Under stress and hypoxia conditions, HIF-1α increases rapidly and regulates intracellular energy metabolism, cell proliferation, apoptosis, and inflammation. Through reprogramming cellular metabolism, HIF-1α can directly or indirectly induce abnormal accumulation of metabolites, changes in cellular epigenetic modifications, and activation of fibrotic signals. HIF-1α protein expression and activity are regulated by various posttranslational modifications. The drugs targeting HIF-1α can regulate the downstream cascade signals by inhibiting HIF-1α activity or promoting its degradation. As the renal fibrosis is affected by renal diseases, different diseases may trigger different mechanisms which will affect the therapy effect. Therefore, comprehensive analysis of the role and contribution of HIF-1α in occurrence and progression of renal fibrosis, and determination the appropriate intervention time of HIF-1α in the process of renal fibrosis are important ideas to explore effective treatment strategies. This study reviews the regulation of HIF-1α and its mediated complex cascade reactions in renal fibrosis, and lists some drugs targeting HIF-1α that used in preclinical studies, to provide new insight for the study of the renal fibrosis mechanism.

The AKI-to-CKD Transition: The Role of Uremic Toxins

After acute kidney injury (AKI), renal function continues to deteriorate in some patients. In a pro-inflammatory and profibrotic environment, the proximal tubules are subject to maladaptive repair. In the AKI-to-CKD transition, impaired recovery from AKI reduces tubular and glomerular filtration and leads to chronic kidney disease (CKD). Reduced kidney secretion capacity is characterized by the plasma accumulation of biologically active molecules, referred to as uremic toxins (UTs). These toxins have a role in the development of neurological, cardiovascular, bone, and renal complications of CKD. However, UTs might also cause CKD as well as be the consequence. Recent studies have shown that these molecules accumulate early in AKI and contribute to the establishment of this pro-inflammatory and profibrotic environment in the kidney. The objective of the present work was to review the mechanisms of UT toxicity that potentially contribute to the AKI-to-CKD transition in each renal compartment.

Sex-specific epigenetic programming in renal fibrosis and inflammation

The growing prevalence of hypertension, heart disease, diabetes, and obesity along with an aging population is leading to a higher incidence of renal diseases in society. Chronic kidney disease (CKD) is characterized mainly by persistent inflammation, fibrosis, and gradual loss of renal function leading to renal failure. Sex is a known contributor to the differences in incidence and progression of CKD. Epigenetic programming is an essential regulator of renal physiology and is critically involved in the pathophysiology of renal injury and fibrosis. Epigenetic signaling integrates intrinsic and extrinsic signals onto the genome, and various environmental and hormonal stimuli, including sex hormones, which regulate gene expression and downstream cellular responses. The most extensively studied epigenetic alterations that play a critical role in renal damage include histone modifications and DNA methylation. Notably, these epigenetic alterations are reversible, making them candidates for potential therapeutic targets for the treatment of renal diseases. Here, we will summarize the current knowledge on sex differences in epigenetic modulation of renal fibrosis and inflammation and highlight some possible epigenetic therapeutic strategies for CKD treatment.

Low levels of circulating methylated IRX3 are related to worse outcome after transcatheter aortic valve implantation in patients with severe aortic stenosis

BACKGROUND

Aortic stenosis (AS) is one of the most common cardiac diseases and major cause of morbidity and mortality in the elderly. Transcatheter aortic valve implantation (TAVI) is performed in such patients with symptomatic severe AS and reduces mortality for the majority of these patients. However, a significant percentage dies within the first two years after TAVI, such that there is an interest to identify parameters, which predict outcome and could guide pre-TAVI patient selection. High levels of cardiac fibrosis have been identified as such independent predictor of cardiovascular mortality after TAVI. Promoter hypermethylation commonly leads to gene downregulation, and the Iroquois homeobox 3 (IRX3) gene was identified in a genome-wide transcriptome and methylome to be hypermethylated and downregulated in AS patients. In a well-described cohort of 100 TAVI patients in which cardiac fibrosis levels were quantified histologically in cardiac biopsies, and which had a follow-up of up to two years, we investigated if circulating methylated DNA of IRX3 in the peripheral blood is associated with cardiac fibrosis and/or mortality in AS patients undergoing TAVI and thus could serve as a biomarker to add information on outcome after TAVI.

RESULTS

Patients with high levels of methylation in circulating IRX3 show a significantly increased survival as compared to patients with low levels of IRX3 methylation indicating that high peripheral IRX3 methylation is associated with an improved outcome. In the multivariable setting, peripheral IRX3 methylation acts as an independent predictor of all-cause mortality. While there is no significant correlation of levels of IRX3 methylation with cardiac death, there is a significant but very weak inverse correlation between circulating IRX3 promoter methylation level and the amount of cardiac fibrosis. Higher levels of peripheral IRX3 methylation further correlated with decreased cardiac IRX3 expression and vice versa.

CONCLUSIONS

High levels of IRX3 methylation in the blood of AS patients at the time of TAVI are associated with better overall survival after TAVI and at least partially reflect myocardial IRX3 expression. Circulating methylated IRX3 might aid as a potential biomarker to help guide both pre-TAVI patient selection and post-TAVI monitoring.

Xanthine oxidase/NADPH oxidase inhibition by hydralazine attenuates acute kidney injury and prevents the transition of acute kidney injury to chronic kidney disease

AIMS

The enhancement of inflammation and reactive oxygen species leads to the damage of renal tubular cells in acute kidney injury (AKI), and the upregulation of inflammation increases the risk of AKI being converted into chronic kidney disease (CKD). Hydralazine has shown renoprotective effects in multiple kidney diseases and was shown to be a potent xanthine oxidase (XO) inhibitor. This study aimed to investigate the mechanisms of hydralazine in ischemia-reperfusion (I/R)-stimulated renal proximal tubular epithelial cells in vitro and in AKI animals in vivo.

MAIN METHODS

The effects of hydralazine in AKI-to-CKD transition were also evaluated. Human renal proximal tubular epithelial cells were stimulated by I/R conditions in vitro. To generate a mouse model of AKI, a right nephrectomy was performed, followed by left renal pedicle I/R using a small atraumatic clamp.

KEY FINDINGS

In the in vitro part, hydralazine could protect renal proximal tubular epithelial cells against insults from the I/R injury through XO/NADPH oxidase inhibition. In the in vivo part, hydralazine preserved renal function in AKI mice and improved the AKI-to-CKD transition by decreasing renal glomerulosclerosis and fibrosis independently of blood pressure lowering. Furthermore, hydralazine exerted antioxidant, anti-inflammatory, and anti-fibrotic effects both in vitro and in vivo.

SIGNIFICANCE

Hydralazine, as a XO/NADPH oxidase inhibitor, could protect renal proximal tubular epithelial cells from the insults of I/R and prevent kidney damage in AKI and AKI-to-CKD. The above experimental studies strengthen the possibility of repurposing hydralazine as a potential renoprotective agent through its antioxidative mechanisms.

Roles of DNA damage in renal tubular epithelial cells injury

The prevalence of renal diseases including acute kidney injury (AKI) and chronic kidney disease (CKD) is increasing worldwide. However, the pathogenesis of most renal diseases is still unclear and effective treatments are still lacking. DNA damage and the related DNA damage response (DDR) have been confirmed as common pathogenesis of acute kidney injury and chronic kidney disease. Reactive oxygen species (ROS) induced DNA damage is one of the most common types of DNA damage involved in the pathogenesis of acute kidney injury and chronic kidney disease. In recent years, several developments have been made in the field of DNA damage. Herein, we review the roles and developments of DNA damage and DNA damage response in renal tubular epithelial cell injury in acute kidney injury and chronic kidney disease. In this review, we conclude that focusing on DNA damage and DNA damage response may provide valuable diagnostic biomarkers and treatment strategies for renal diseases including acute kidney injury and chronic kidney disease.

DNA methylation enzymes in the kidneys of male and female BTBR ob/ob mice

Diabetic kidney disease (DKD) is the leading cause of the end-stage renal disease. Recent studies have shown that epigenetic modifications contribute to alterations in gene expression and the development of DKD. This study aimed to show an expression profile of key DNA (de)methylation enzymes (DNMT, TET proteins) and their differences between sexes under obesity and diabetic condition. Male and female black and tan brachyury (BTBR) ob/ob mice and their corresponding wild-type littermates (BTBR WT) were studied until 16 weeks of age. Metabolic parameters, kidney morphophysiology and the expression of fibrotic markers and epigenetic enzymes were studied in whole kidney tissue or specifically in the glomerulus. The results showed sexual dimorphism in the development of metabolic disease and in kidney morphophysiology. Female mice have a different profile of DNMTs expression in both WT and obese/diabetic condition. Furthermore, metabolic condition negatively modulated the glomerular expression of TET1 and TET3 only in females. To our knowledge, this is the first study that shows a kidney profile of the expression of key (de)methylation enzymes, DNMTs and TETs, in the BTBR ob/ob experimental model of DKD and its association with sex. The knowledge of this epigenetic profile may help future research to understand the pathophysiology of DKD in males and females.

Akt1 is involved in renal fibrosis and tubular apoptosis in a murine model of acute kidney injury-to-chronic kidney disease transition

Maladaptive repair after acute kidney injury (AKI) can predispose patients to chronic kidney disease (CKD). However, the molecular mechanism underlying the AKI-to-CKD transition remains unclear. The Akt signaling pathway has been reported to be involved in the pathological processes of both AKI and CKD. In this study, we investigated the role of Akt1 in a murine model of the AKI-to-CKD transition. Wild-type (WT) and Akt1^-/- mice were subjected to unilateral ischemia-reperfusion injury (UIRI), with their kidneys harvested after two days and two, four, and six weeks after UIRI. The dynamic changes in tubulointerstitial fibrosis, markers of tubular epithelial-mesenchymal transition (EMT), and tubular apoptosis were investigated. Akt1 of the three Akt isoforms was activated during the AKI-to-CKD transition. After UIRI, tubulointerstitial fibrosis and tubular EMT were significantly increased in WT mice, but were attenuated in Akt1^-/- mice. The expression of the transforming growth factor (TGF)-β1/Smad was increased in both WT and Akt1^-/- mice, but was not different between the two groups. The levels of phosphorylated glycogen synthase kinase (GSK)-3β, Snail, and β-catenin in the Akt1^-/- mice were lower than those in the WT mice. The number of apoptotic tubular cells and the expression of cleaved caspase-3/Bax were both lower in Akt1^-/- mice than in WT mice. Genetic deletion of Akt1 was associated with attenuation of tubulointerstitial fibrosis, tubular EMT, and tubular apoptosis during the AKI-to-CKD transition. These findings were associated with TGF-β1/Akt1/GSK-3β/(Snail and β-catenin) signaling independent of TGF-β1/Smad signaling. Thus, Akt1 signaling could serve as a potential therapeutic target for inhibiting the AKI-to-CKD transition.

Inhibition of ALKBH5 attenuates I/R-induced renal injury in male mice by promoting Ccl28 m6A modification and increasing Treg recruitment

Ischemia reperfusion injury (IRI) is a common cause of acute kidney injury (AKI). The role of N^6-methyladenosine (m6A) modification in AKI remains unclear. Here, we characterize the role of AlkB homolog 5 (ALKBH5) and m6A modification in an I/R-induced renal injury model in male mice. Alkbh5-knockout mice exhibit milder pathological damage and better renal function than wild-type mice post-IRI, whereas Alkbh5-knockin mice show contrary results. Also conditional knockout of Alkbh5 in the tubular epithelial cells alleviates I/R-induced AKI and fibrosis. CCL28 is identified as a target of ALKBH5. Furthermore, Ccl28 mRNA stability increases with Alkbh5 deficiency, mediating by the binding of insulin-like growth factor 2 binding protein 2. Treg recruitment is upregulated and inflammatory cells are inhibited by the increased CCL28 level in IRI-Alkbh5^fl/flKsp^Cre mice. The ALKBH5 inhibitor IOX1 exhibits protective effects against I/R-induced AKI. In summary, inhibition of ALKBH5 promotes the m6A modifications of Ccl28 mRNA, enhancing its stability, and regulating the Treg/inflammatory cell axis. ALKBH5 and this axis is a potential AKI treatment target.

Hydralazine-augmented contrast ultrasound imaging improves the detection of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) detection with B-mode and contrast-enhanced ultrasound (CUS) imaging often varies between subjects, especially in patients with background cirrhosis. Various factors contribute to this variability, including the tumor blood flow, tumor size, internal echoes, and its location in livers with diffuse fibro-cirrhotic changes.

OBJECTIVE

Towards improving lesion detection, this study evaluates a vasodilator, hydralazine, to enhance the visibility of HCC by reducing its blood flow relative to the surrounding liver tissue.

METHODS

HCC were analyzed for tumor visibility measured for B-mode, CUS, and hydralazine-augmented-contrast ultrasound (HyCUS) in an autochthonous HCC rat model. 21 tumors from 12 rats were studied. B-mode and CUS images were acquired before hydralazine injection. Rats received an intravenous hydralazine injection of 5 mg/kg, then images were acquired 20 min later. Four rats were used as controls. The difference in echo intensity of the lesion and the surrounding tissue was used to determine the visibility index (VI).

RESULTS

The visibility index for HCC was found to be significantly improved with the use of HyCUS imaging compared to traditional B-mode and CUS imaging. The visibility index for HCC was 16.5 ± 2.8 for HyCUS, compared to 5.3 ± 4.8 for B-mode and 4.1 ± 3.8 for CUS. The differences between HyCUS and the other imaging modalities were statistically significant, with p-values of 0.001 and 0.02, respectively. Additionally, when compared to control cases, HyCUS showed higher discrimination of HCC (VI = 6.4 ± 1.2) with a p-value of 0.003, while B-mode (VI = 6.7 ± 1.4, p = 0.5) and CUS (VI = 6.4 ± 1.2, p = 0.3) showed lower discrimination.

CONCLUSION

Vascular blood flow modulation by hydralazine enhances the visibility of HCC. HyCUS offers a potential problem-solving method for detecting HCC when B-mode and CUS are unsuccessful, especially with background fibro-cirrhotic liver disease. Future evaluation of the approach in humans will determine its translatability for clinical applications.

Reactive Oxygen Species- and Cell-Free DNA-Scavenging Mn3O4 Nanozymes for Acute Kidney Injury Therapy

Reactive oxygen species (ROS) scavenging therapy toward acute kidney injury (AKI) is promising, but no effective ROS scavenging drug has been developed yet. Moreover, cell-free DNA (cfDNA) is also involved in AKI, but the corresponding therapies have not been well developed. To tackle these challenges, Mn₃O₄ nanoflowers (Nfs) possessing both ROS and cfDNA scavenging activities were developed for better AKI protection as follows. First, Mn₃O₄ Nfs could protect HK2 cells through cascade ROS scavenging (dismutating ^·O₂^- into H₂O₂ by superoxide dismutase-like activity and then decomposing H₂O₂ by catalase-like activity). Second, Mn₃O₄ Nfs could efficiently adsorb cfDNA and then decrease the inflammation caused by cfDNA. Combined, remarkable therapeutic efficacy was achieved in both cisplatin-induced and ischemia-reperfusion AKI murine models. Furthermore, Mn₃O₄ Nfs could be used for the T₁-MRI real-time imaging of AKI. This study not only offered a promising treatment for AKI but also showed the translational potential of nanozymes.

Potential Impacts of Hydralazine as a Novel Antioxidant on Cardiovascular and Renal Disease-Beyond Vasodilation and Blood Pressure Lowering

Hydralazine is a traditional antihypertensive drug that was developed several decades ago. Its most well-known effect is blood pressure lowering by arterial vasodilation. While mainly used an adjunct treatment for clinical hypertension or chronic heart failure, this old drug has also shown potential as a repurposing drug for the atherosclerosis vascular disease and various kidney diseases. Recent experimental studies suggest that hydralazine exerts antioxidative, anti-apoptotic, and HIF-1α stabilization effects for angiogenesis and vascular protection. Hydralazine also exerts reno-protective effects via its antioxidation, DNA demethylation, and anti-inflammation abilities. The above evidence provides advanced rationales for new applications of this drug beyond blood pressure lowering and arterial vasodilation. Here, we summarized the recent experimental advances in the use of hydralazine for either a vascular disease or kidney diseases, or both. Given the wide populations of people with cardiovascular and/or kidney diseases, future studies are worth validating the potential impacts of hydralazine on the clinical outcomes in selected patients.

Low-dose 5-aza-2'-deoxycytidine protects against early renal injury by increasing klotho expression

Aim: To explore the effect of the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (Aza) on early renal injury. Materials & methods: Cell damage and inflammation are features of early renal injury. The apoptosis and inflammation in hypoxia/reoxygenation (H/R)-induced human proximal tubular epithelial cells (HK-2) and ischemia-reperfusion kidney were studied, and expression of the protein klotho was investigated. Results: Aza induced HK-2 apoptosis in a dose-dependent manner, but low-dose Aza attenuated the apoptosis and inflammation in H/R-induced HK-2 cells and ischemia-reperfusion kidney. Low-dose Aza ameliorated renal function in mice with renal ischemia-reperfusion injury. Meanwhile, low-dose Aza upregulated klotho expression in H/R-induced HK-2 cells and ischemia-reperfusion kidney. Klotho knockdown abrogated the effects of low-dose Aza on apoptosis and inflammation. Conclusion: Low-dose Aza protects against renal early injury by increasing klotho expression.

Low-dose hydralazine reduces albuminuria and glomerulosclerosis in a mouse model of obesity-related chronic kidney disease

AIM

To determine, using a mouse model of obesity, whether low-dose hydralazine prevents obesity-related chronic kidney disease (CKD).

METHODS

From 8 weeks of age, male C57BL/6 mice received a high-fat diet (HFD) or chow, with or without low-dose hydralazine (25 mg/L) in drinking water, for 24 weeks. Biometric and metabolic variables, renal function and structural changes, renal global DNA methylation, DNA methylation profile and markers of renal fibrosis, injury, inflammation and oxidative stress were assessed.

RESULTS

The HFD-fed mice developed obesity, with glucose intolerance, hyperinsulinaemia and dyslipidaemia. Obesity increased albuminuria and glomerulosclerosis, which were significantly ameliorated by low-dose hydralazine in the absence of a blood pressure-lowering effect. Obesity increased renal global DNA methylation and this was attenuated by low-dose hydralazine. HFD-induced changes in methylation of individual loci were also significantly reversed by low-dose hydralazine. Obese mice demonstrated increased markers of kidney fibrosis, inflammation and oxidative stress, but these markers were not significantly improved by hydralazine.

CONCLUSION

Low-dose hydralazine ameliorated HFD-induced albuminuria and glomerulosclerosis, independent of alterations in biometric and metabolic variables or blood pressure regulation. Although the precise mechanism of renoprotection in obesity is unclear, an epigenetic basis may be implicated. These data support repurposing hydralazine as a novel therapy to prevent CKD progression in obese patients.

Oncogenic collagen I homotrimers from cancer cells bind to α3β1 integrin and impact tumor microbiome and immunity to promote pancreatic cancer

In contrast to normal type I collagen (Col1) heterotrimer (α1/α2/α1) produced by fibroblasts, pancreatic cancer cells specifically produce unique Col1 homotrimer (α1/α1/α1). Col1 homotrimer results from epigenetic suppression of the Col1a2 gene and promotes oncogenic signaling, cancer cell proliferation, tumor organoid formation, and growth via α3β1 integrin on cancer cells, associated with tumor microbiome enriched in anaerobic Bacteroidales in hypoxic and immunosuppressive tumors. Deletion of Col1 homotrimers increases overall survival of mice with pancreatic ductal adenocarcinoma (PDAC), associated with reprograming of the tumor microbiome with increased microaerophilic Campylobacterales, which can be reversed with broad-spectrum antibiotics. Deletion of Col1 homotrimers enhances T cell infiltration and enables efficacy of anti-PD-1 immunotherapy. This study identifies the functional impact of Col1 homotrimers on tumor microbiome and tumor immunity, implicating Col1 homotrimer-α3β1 integrin signaling axis as a cancer-specific therapeutic target.

Crosstalk between kidney and liver in non-alcoholic fatty liver disease: mechanisms and therapeutic approaches

Liver and kidney are vital organs that maintain homeostasis and injury to either of them triggers pathogenic pathways affecting the other. For example, non-alcoholic fatty liver disease (NAFLD) promotes the progression of chronic kidney disease (CKD), vice versa acute kidney injury (AKI) endorses the induction and progression of liver dysfunction. Progress in clinical and basic research suggest a role of excessive fructose intake, insulin resistance, inflammatory cytokines production, activation of the renin-angiotensin system, redox imbalance, and their impact on epigenetic regulation of gene expression in this context. Recent developments in experimental and clinical research have identified several biochemical and molecular pathways for AKI-liver interaction, including altered liver enzymes profile, metabolic acidosis, oxidative stress, activation of inflammatory and regulated cell death pathways. This review focuses on the current preclinical and clinical findings on kidney-liver crosstalk in NAFLD-CKD and AKI-liver dysfunction settings and highlights potential molecular mechanisms and therapeutic targets.

Folic acid-targeted pluronic F127 micelles improve oxidative stress and inhibit fibrosis for increasing AKI efficacy

The oxidative stress and activation of the fibrosis pathway are essential pathological mechanisms of acute kidney injury (AKI). In this article, we designed a drug delivery system that could effectively improve oxidative stress and relieve fibrosis by the combination of precise targeting, solubilization, and reducing the toxicity of nano-transport system to strengthen the efficacy of AKI. Folic acid (FA) was used as the targeting molecule, and curcumin (Cur) and resveratrol (Res), which are Chinese medicine monomers with anti-inflammatory and antioxidant effects, were used as model drugs. Here, the targeting nanosystem (Cur/Res@FA-F127/TPGS) co-loaded with Cur and Res was successfully synthesized. Finally, the comprehensive therapeutic effect of the nanosystem was evaluated through the targeted and pharmacodynamic researches on the AKI models induced by cisplatin (CDDP) in vitro and in vivo. The studies in vitro proved that the nanosystem could not only specifically target HK-2 cells and promote the effective accumulation of Cur and Res in the kidney, but also effectively improve oxidative stress by eliminating reactive oxygen species (ROS), stabilizing mitochondrial membrane potential (MMP), and reducing the expression of apoptosis-related proteins. The studies in vivo showed that the nanosystem could effectively play the role of anti-oxidation, anti-inflammatory and alleviate fibrosis to reduce the apoptosis and necrosis of renal tubular cells. The nanosystem could coordinately repair damaged HK-2 cells by improving oxidative stress, inhibiting inflammation and tissue fibrosis, which provided a new idea for the treatment of AKI.

Antioxidation and Nrf2-mediated heme oxygenase-1 activation contribute to renal protective effects of hydralazine in diabetic nephropathy

Reactive oxygen species (ROS) and oxidative stress are associated with the progression of diabetic nephropathy (DN). Hydralazine is an antihypertensive agent and may act as a xanthine oxidase (XO) inhibitor to reduce uric acid levels in a mouse renal injury model. This study aimed to investigate the potential mechanisms of hydralazine in experimental DN. Streptozotocin-induced diabetic mice were fed a high-fat diet to generate DN. Human renal proximal tubular epithelial cells were used in vitro. Nitrendipine and allopurinol which can reduce blood pressure or XO activity levels, were used as two positive controls. Hydralazine downregulated NF-κB/p38 signaling pathways and reduced TNF-α/IL-6 expressions in high glucose-stimulated renal proximal tubular epithelial cells. Hydralazine reduced in vitro ROS production via XO inhibition and nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated heme oxygenase (HO)-1 activation. Furthermore, hydralazine reduced high glucose-induced apoptosis by downregulating PARP/caspase-3 signaling. Hydralazine and allopurinol but not nitrendipine reduced serum uric acid levels and systemic inflammation. Hydralazine and allopurinol treatment improved renal function with decreased urinary albumin-to-creatinine ratios, glomerular hypertrophy, glomerulosclerosis, and fibrosis in the kidney of DN mice. While both hydralazine and allopurinol downregulated XO and NADPH oxidase expression, only hydralazine upregulated Nrf2/HO-1 renal expression, suggesting the additional effects of hydralazine independent of XO/ NADPH oxidase inhibition. In conclusion, hydralazine protected renal proximal tubular epithelial cells against the insults of high glucose and prevented renal damage via XO/NADPH oxidase inhibition and Nrf-2/HO-1 activation, suggesting the comprehensive antioxidation and anti-inflammation mechanisms for the management of DN.

Are Alterations in DNA Methylation Related to CKD Development?

The modifications in genomic DNA methylation are involved in the regulation of normal and pathological cellular processes. The epigenetic regulation stimulates biological plasticity as an adaptive response to variations in environmental factors. The role of epigenetic changes is vital for the development of some diseases, including atherogenesis, cancers, and chronic kidney disease (CKD). The results of studies presented in this review have suggested that altered DNA methylation can modulate the expression of pro-inflammatory and pro-fibrotic genes, as well those essential for kidney development and function, thus stimulating renal disease progression. Abnormally increased homocysteine, hypoxia, and inflammation have been suggested to alter epigenetic regulation of gene expression in CKD. Studies of renal samples have demonstrated the relationship between variations in DNA methylation and fibrosis and variations in estimated glomerular filtration rate (eGFR) in human CKD. The unravelling of the genetic-epigenetic profile would enhance our understanding of processes underlying the development of CKD. The understanding of multifaceted relationship between DNA methylation, genes expression, and disease development and progression could improve the ability to identify individuals at risk of CKD and enable the choice of appropriate disease management.

The functional activity of donor kidneys is negatively regulated by microribonucleic acid-451 in different perfusion methods to inhibit adenosine triphosphate metabolism and the proliferation of HK2 cells

This study explored the regulation of different perfusion methods on ischemia-reperfusion injury in donor kidneys. In this study, renal cortical/medullary tissue specimens were collected from porcine kidneys donors using different perfusion methods at various time points. Hematoxylin and eosin (H&E) staining was used to test the histological differences. Differentially expressed micro-ribonucleic acids (miRNAs) were identified by miRNA transcriptome sequencing. Reverse transcription-polymerase chain reaction (RT-PCR) tests were used to verify the changes in miRNAs in the kidney tissue taken from different perfusion groups. The related signaling pathways and the changes in the cell functions of different perfusion groups were analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) /Gene Ontology (GO) bioinformatics analyses. The effects of miRNA overexpression on the metabolism and proliferation of HK2 cells were detected by ATP kit and MTT assay. The H&E staining results showed that there were essentially no differences in the tissue samples among different perfusion groups at and before 12 h compared with a control group. The quantitative PCR results revealed that there was essentially no change in the expression of ssc-miR-451, ssc-miR-1285, and ssc-miR-486 in the cis infusion or joint infusion kidney groups, and their expression was significantly down-regulated over time in the trans-infusion kidney group. The bioinformatics analysis showed that the cellular component, molecular function, and biological processes of the kidney tissue, which had been perfused using three methods, had been consistently affected. The most significant changes after perfusion occurred in the intracellular metabolism signaling pathways. Furthermore, the energy metabolism and proliferation of the HK2 cells were significantly inhibited after the overexpression of miR-451. Specific miRNA markers, such as miR-451, may play a negative regulatory role in cell metabolism following the perfusion of kidney transplants using different methods.

Regenerative Drug Discovery Using Ear Pinna Punch Wound Model in Mice

The ear pinna is a complex tissue consisting of the dermis, cartilage, muscles, vessels, and nerves. Ear pinna healing is a model of regeneration in mammals. In some mammals, including rabbits, punch wounds in the ear pinna close spontaneously; in common-use laboratory mice, they remain for life. Agents inducing ear pinna healing are potential regenerative drugs. We tested the effects of selected bioactive agents on 2 mm ear pinna wound closure in BALB/c mice. Our previous research demonstrated that a DNA methyltransferase inhibitor, zebularine, remarkably induced ear pinna regeneration. Although experiments with two other demethylating agents, RG108 and hydralazine, were unsuccessful, a histone deacetylase inhibitor, valproic acid, was another epigenetic agent found to increase ear hole closure. In addition, we identified a pro-regenerative activity of 4-ketoretinoic acid, a retinoic acid metabolite. Attempts to counteract the regenerative effects of the demethylating agent zebularine, with folates as methyl donors, failed. Surprisingly, a high dose of methionine, another methyl donor, promoted ear hole closure. Moreover, we showed that the regenerated areas of ear pinna were supplied with nerve fibre networks and blood vessels. The ear punch model proved helpful in testing the pro-regenerative activities of small-molecule compounds and observations of peripheral nerve regeneration.

Hyaluronan, a double-edged sword in kidney diseases

Over the years, hyaluronic acid (HA) has emerged as an important molecule in nephrological and urological studies involving extracellular matrix (ECM) organization, inflammation, tissue regeneration, and viral sensing. During this time, many have noted the perplexing double-edged nature of the molecule, at times promoting pro-fibrotic events and at other times promoting anti-fibrotic events. Different molecular weights of HA can be attributed to these disparities, though most studies have yet to focus on this subtlety. With regard to the kidney, HA is induced in the initial response phase of injury and is subsequently decreased during disease progression of AKI, CKD, and diabetic nephropathy. These and other kidney diseases force patients, particularly pediatric patients, to face dialysis, surgical procedures, and ultimately, transplant. To summarize the current literature for researchers and pediatric nephrologists, this review aims to expound HA and elucidate its paradoxical effects in multiple kidney diseases using studies that emphasize HA molecular weight when available.

Therapies Targeting Epigenetic Alterations in Acute Kidney Injury-to-Chronic Kidney Disease Transition

Acute kidney injury (AKI) was previously thought to be a merely transient event; however, recent epidemiological evidence supports the existence of a causal relationship between AKI episodes and subsequent progression to chronic kidney disease (CKD). Although the pathophysiology of this AKI-to-CKD transition is not fully understood, it is mediated by the interplay among multiple components of the kidney including tubular epithelial cells, endothelial cells, pericytes, inflammatory cells, and myofibroblasts. Epigenetic alterations including histone modification, DNA methylation, non-coding RNAs, and chromatin conformational changes, are also expected to be largely involved in the pathophysiology as a “memory” of the initial injury that can persist and predispose to chronic progression of fibrosis. Each epigenetic modification has a great potential as a therapeutic target of AKI-to-CKD transition; timely and target-specific epigenetic interventions to the various temporal stages of AKI-to-CKD transition will be the key to future therapeutic applications in clinical practice. This review elaborates on the latest knowledge of each mechanism and the currently available therapeutic agents that target epigenetic modification in the context of AKI-to-CKD transition. Further studies will elucidate more detailed mechanisms and novel therapeutic targets of AKI-to-CKD transition.

Hydralazine protects the heart against acute ischaemia/reperfusion injury by inhibiting Drp1-mediated mitochondrial fission

AIMS

Genetic and pharmacological inhibition of mitochondrial fission induced by acute myocardial ischaemia/reperfusion injury (IRI) has been shown to reduce myocardial infarct size. The clinically used anti-hypertensive and heart failure medication, hydralazine, is known to have anti-oxidant and anti-apoptotic effects. Here, we investigated whether hydralazine confers acute cardioprotection by inhibiting Drp1-mediated mitochondrial fission.

METHODS AND RESULTS

Pre-treatment with hydralazine was shown to inhibit both mitochondrial fission and mitochondrial membrane depolarisation induced by oxidative stress in HeLa cells. In mouse embryonic fibroblasts (MEFs), pre-treatment with hydralazine attenuated mitochondrial fission and cell death induced by oxidative stress, but this effect was absent in MEFs deficient in the mitochondrial fission protein, Drp1. Molecular docking and surface plasmon resonance studies demonstrated binding of hydralazine to the GTPase domain of the mitochondrial fission protein, Drp1 (KD 8.6±1.0 µM), and inhibition of Drp1 GTPase activity in a dose-dependent manner. In isolated adult murine cardiomyocytes subjected to simulated IRI, hydralazine inhibited mitochondrial fission, preserved mitochondrial fusion events, and reduced cardiomyocyte death (hydralazine 24.7±2.5% vs. control 34.1±1.5%, P=0.0012). In ex vivo perfused murine hearts subjected to acute IRI, pre-treatment with hydralazine reduced myocardial infarct size (as % left ventricle: hydralazine 29.6±6.5% vs. vehicle control 54.1±4.9%, P=0.0083), and in the murine heart subjected to in vivo IRI, the administration of hydralazine at reperfusion, decreased myocardial infarct size (as % area-at-risk: hydralazine 28.9±3.0% vs. vehicle control 58.2±3.8%, P<0.001).

CONCLUSION

We show that, in addition to its antioxidant and anti-apoptotic effects, hydralazine, confers acute cardioprotection by inhibiting IRI-induced mitochondrial fission, raising the possibility of repurposing hydralazine as a novel cardioprotective therapy for improving post-infarction outcomes.

Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease

Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.

The Long Noncoding RNA-H19 Mediates the Progression of Fibrosis from Acute Kidney Injury to Chronic Kidney Disease by Regulating the miR-196a/Wnt/β-Catenin Signaling

INTRODUCTION

Long noncoding RNAs (lncRNAs) have been reported to be involved in the occurrence and development of various diseases. This study was to investigate the role of lncRNA-H19 in the transition from acute kidney injury (AKI) to chronic kidney disease (CKD) and its underlying mechanism.

METHODS

Bilateral renal pedicle ischemia-reperfusion injury (IRI) was used to establish the IRI-AKI model in C57BL/6 mice. The expression levels of lncRNA-H19, miR-196a-5p, α-SMA, collagen I, Wnt1, and β-catenin in mouse kidney tissues and fibroblasts were determined by quantitative real-time PCR and Western blotting. The degree of renal fibrosis was evaluated by hematoxylin and eosin staining. The interaction between lncRNA-H19 and miR-196a-5p was verified by bioinformatics analysis and luciferase reporter assay. Immunohistochemistry and immunofluorescence were used to evaluate the expression of α-SMA and collagen I in kidney tissues and fibroblasts of mice.

RESULTS

lncRNA-H19 is upregulated, and miR-196a-5p is downregulated in kidney tissues of IRI mice. Moreover, miR-196a-5p is a direct target of lncRNA-H19. lncRNA-H19 overexpression promotes kidney fibrosis and activates fibroblasts during AKI-CKD development, while miR-196a-5p overexpression reversed these effects in vitro. Furthermore, lncRNA-H19 overexpression significantly upregulates Wnt1 and β-catenin expression in kidney tissues and fibroblasts of IRI mice, while miR-196a-5p overexpression downregulates Wnt1 and β-catenin expression in kidney tissues and fibroblasts of IRI mice.

CONCLUSION

lncRNA-H19 induces kidney fibrosis during AKI-CKD by regulating the miR-196a-5p/Wnt/β-catenin signaling pathway.

Hydralazine attenuates renal inflammation in diabetic rats with ischemia/reperfusion acute kidney injury

Acute kidney injury (AKI) is one of the major complications with increased oxidative stress and inflammation in diabetic patients. Hyperglycemia stimulates the formation of advanced glycation end products (AGEs). However, hyperglycemia directly triggers the interaction between AGEs and transmembrane AGEs receptors (RAGE), which enhances oxidative stress and increases the production of inflammatory substances. Therefore, diabetes plays a pivotal role in kidney injury. Hydralazine, a vasodilator and antihypertensive drug, was found to have the ability to reduce ROS, oxidative stress, and inflammation. We applied Hydralazine co-culture with AGEs in rat mesangial cells (RMC) and to renal ischemia/reperfusion(I/R) injury models in streptozotocin-induced diabetic rats. Hydralazine significantly decreased AGEs-induced RAGE, iNOS, and COX-2 expressions in RMC. Compared to the diabetic with AKI group, hydralazine decreased inflammation-related protein, and JAK2, STAT3 signaling in rat kidney tissue. Our studies indicate that Hydralazine has the potential to become a beneficial drug in the treatment of diabetic acute kidney injury.

Chronic Kidney Disease: Strategies to Retard Progression

Chronic kidney disease (CKD), defined as the presence of irreversible structural or functional kidney damages, increases the risk of poor outcomes due to its association with multiple complications, including altered mineral metabolism, anemia, metabolic acidosis, and increased cardiovascular events. The mainstay of treatments for CKD lies in the prevention of the development and progression of CKD as well as its complications. Due to the heterogeneous origins and the uncertainty in the pathogenesis of CKD, efficacious therapies for CKD remain challenging. In this review, we focus on the following four themes: first, a summary of the known factors that contribute to CKD development and progression, with an emphasis on avoiding acute kidney injury (AKI); second, an etiology-based treatment strategy for retarding CKD, including the approaches for the common and under-recognized ones; and third, the recommended approaches for ameliorating CKD complications, and the final section discusses the novel agents for counteracting CKD progression.

Epigenetics in kidney diseases

Epigenetics examines heritable changes in DNA and its associated proteins except mutations in gene sequence. Epigenetic regulation plays fundamental roles in kidney cell biology through the action of DNA methylation, chromatin modification via epigenetic regulators and non-coding RNA species. Kidney diseases, including acute kidney injury, chronic kidney disease, diabetic kidney disease and renal fibrosis are multistep processes associated with numerous molecular alterations even in individual kidney cells. Epigenetic alterations, including anomalous DNA methylation, aberrant histone alterations and changes of microRNA expression all contribute to kidney pathogenesis. These changes alter the genome-wide epigenetic signatures and disrupt essential pathways that protect renal cells from uncontrolled growth, apoptosis and development of other renal associated syndromes. Molecular changes impact cellular function within kidney cells and its microenvironment to drive and maintain disease phenotype. In this chapter, we briefly summarize epigenetic mechanisms in four kidney diseases including acute kidney injury, chronic kidney disease, diabetic kidney disease and renal fibrosis. We primarily focus on current knowledge about the genome-wide profiling of DNA methylation and histone modification, and epigenetic regulation on specific gene(s) in the pathophysiology of these diseases and the translational potential of identifying new biomarkers and treatment for prevention and therapy. Incorporating epigenomic testing into clinical research is essential to elucidate novel epigenetic biomarkers and develop precision medicine using emerging therapies.

Epigenetic Modification Drives Acute Kidney Injury-to-Chronic Kidney Disease Progression

Acute kidney injury (AKI) is a common clinical critical disease. Due to its high morbidity, increasing risk of complications, high mortality rate, and high medical costs, it has become a global concern for human health problems. Initially, researchers believed that kidneys have a strong ability to regenerate and repair, but studies over the past 20 years have found that kidneys damaged by AKI are often incomplete or even unable to repair. Even when serum creatinine returns to baseline levels, renal structural damage persists for a long time, leading to the development of chronic kidney disease (CKD). The mechanism of AKI-to-CKD transition has not been fully elucidated. As an important regulator of gene expression, epigenetic modifications, such as histone modification, DNA methylation, and noncoding RNAs, may play an important role in this process. Alterations in epigenetic modification are induced by hypoxia, thus promoting the expression of inflammatory factor-related genes and collagen secretion. This review elaborated the role of epigenetic modifications in AKI-to-CKD progression, the diagnostic value of epigenetic modifications biomarkers in AKI chronic outcome, and the potential role of targeting epigenetic modifications in the prevention and treatment of AKI to CKD, in order to provide ideas for the subsequent establishment of targeted therapeutic strategies to prevent the progression of renal tubular-interstitial fibrosis.

Novel Role of Gestational Hydralazine in Limiting Maternal and Dietary Obesity-Related Chronic Kidney Disease

BACKGROUND

Maternal obesity is a risk factor for chronic kidney disease (CKD) in offspring, underpinning the theory of the developmental origins of health and disease. DNA methylation has been implicated in the programming of adult chronic disease by maternal obesity, therefore, DNA demethylating agents may mitigate offspring risk of disease. In rodent models, low-dose hydralazine has previously been shown to reduce renal fibrosis via DNA demethylation. We used mouse models of maternal obesity and offspring obesity to determine whether administration of low-dose hydralazine during gestation can prevent fetal programming of CKD in offspring.

METHODS

Female C57BL/6 mice received high fat diet (HFD) or chow prior to mating, during gestation and lactation. During gestation, dams received subcutaneous hydralazine (5 mg/kg) or saline thrice-weekly. Male offspring weaned to HFD or chow, which continued until endpoint at 32 weeks. Biometric and metabolic parameters, renal global DNA methylation, renal functional and structural changes, and renal markers of fibrosis, inflammation and oxidative stress were assessed at endpoint.

RESULTS

Offspring exposed to maternal obesity or diet-induced obesity had significantly increased renal global DNA methylation, together with other adverse renal effects including albuminuria, glomerulosclerosis, renal fibrosis, and oxidative stress. Offspring exposed to gestational hydralazine had significantly reduced renal global DNA methylation. In obese offspring of obese mothers, gestational hydralazine significantly decreased albuminuria, glomerulosclerosis, and serum creatinine. Obese offspring of hydralazine-treated lean mothers displayed reduced markers of renal fibrosis and oxidative stress.

CONCLUSION

Gestational hydralazine decreased renal global DNA methylation and exerted renoprotective effects in offspring. This supports a potential therapeutic effect of hydralazine in preventing maternal obesity or dietary obesity-related CKD, through an epigenetic mechanism.

Hydralazine augmented ultrasound hyperthermia for the treatment of hepatocellular carcinoma

This study investigates the use of hydralazine to enhance ultrasound hyperthermia for the treatment of hepatocellular carcinoma (HCC) by minimizing flow-mediated heat loss from the tumor. Murine HCC tumors were treated with a continuous mode ultrasound with or without an intravenous administration of hydralazine (5 mg/kg). Tumor blood flow and blood vessels were evaluated by contrast-enhanced ultrasound (CEUS) imaging and histology, respectively. Hydralazine markedly enhanced ultrasound hyperthermia through the disruption of tumor blood flow in HCC. Ultrasound treatment with hydralazine significantly reduced peak enhancement (PE), perfusion index (PI), and area under the curve (AUC) of the CEUS time-intensity curves by 91.9 ± 0.9%, 95.7 ± 0.7%, and 96.6 ± 0.5%, compared to 71.4 ± 1.9%, 84.7 ± 1.1%, and 85.6 ± 0.7% respectively without hydralazine. Tumor temperature measurements showed that the cumulative thermal dose delivered by ultrasound treatment with hydralazine (170.8 ± 11.8 min) was significantly higher than that without hydralazine (137.7 ± 10.7 min). Histological assessment of the ultrasound-treated tumors showed that hydralazine injection formed larger hemorrhagic pools and increased tumor vessel dilation consistent with CEUS observations illustrating the augmentation of hyperthermic effects by hydralazine. In conclusion, we demonstrated that ultrasound hyperthermia can be enhanced significantly by hydralazine in murine HCC tumors by modulating tumor blood flow. Future studies demonstrating the safety of the combined use of ultrasound and hydralazine would enable the clinical translation of the proposed technique.

Role of Akt1 in renal fibrosis and tubular dedifferentiation during the progression of acute kidney injury to chronic kidney disease

BACKGROUND/AIMS

Acute kidney injury (AKI) is an underestimated yet important risk factor for the development of chronic kidney disease (CKD), characterized by tubulointerstitial fibrosis and tubular dedifferentiation. Tubular dedifferentiation, which is associated with the loss of epithelial markers and the gain of mesenchymal features, is thought to be involved in tubulointerstitial fibrosis. As protein kinase B/Akt is involved in the development of CKD, we investigated the role of Akt1, one of the three Akt isoforms, in a murine model of AKI-to-CKD progression.

METHODS

We subjected C57BL/6 male mice to unilateral ischemia-reperfusion injury (UIRI) and harvested their kidneys after 6 weeks. Mice were divided into four groups, namely, wild-type (WT) UIRI, Akt1-/- UIRI, WT sham, and Akt1-/- sham.

RESULTS

Akt1 (but not Akt2 or Akt3) was markedly activated in WT UIRI mice than in WT sham mice. Tubulointerstitial fibrosis and tubular dedifferentiation significantly increased in WT UIRI mice, but were attenuated in Akt1-/- UIRI mice. Both WT UIRI and Akt1-/- UIRI mice showed markedly upregulated transforming growth factor-β1 (TGF-β1)/Smad signaling compared with WT sham mice. However, TGF-β1/Smad expression did not differ between the two groups. The levels of phosphorylated GSK-3β, β-catenin, and Snail were attenuated in Akt1-/- UIRI mice compared with those in WT UIRI mice.

CONCLUSION

Deletion of Akt1 results in the attenuation of renal fibrosis and tubular dedifferentiation, independent of TGF-β1/Smad signaling, during AKI-to-CKD progression in a UIRI without contralateral nephrectomy model. Thus, Akt1 may serve as a therapeutic target in AKI-to-CKD progression.

Low-dose hydralazine during gestation reduces renal fibrosis in rodent offspring exposed to maternal high fat diet

BACKGROUND

Maternal high fat diet (HFD) promotes chronic kidney disease (CKD) in offspring. This is in accordance with the theory of fetal programming, which suggests adverse conditions occurring in utero predispose offspring to chronic conditions later in life. DNA methylation has been proposed as a key mechanism by which fetal programming occurs and is implicated in CKD progression. DNA demethylating drugs may interrupt the fetal programming of CKD by maternal obesity. Hydralazine, an antihypertensive agent, demethylates DNA at low doses which do not reduce blood pressure. We used a mouse model of maternal obesity to determine whether gestational administration of low-dose hydralazine to mothers can prevent CKD in offspring.

METHODS

C57BL/6 dams received HFD or chow from 6 weeks prior to mating and were administered subcutaneous hydralazine (5mg/kg) or saline thrice weekly during gestation. Male offspring were weaned to chow and were sacrificed at either postnatal week 9 or week 32. Biometric and metabolic parameters, renal global DNA methylation, renal structural and functional changes and markers of fibrosis, oxidative stress and inflammation were measured in offspring at weeks 9 and 32.

RESULTS

In week 9 offspring, maternal HFD consumption did not significantly alter anthropometric or metabolic parameters, or renal global DNA methylation. Week 32 offspring had increased renal global DNA methylation, together with albuminuria, glomerulosclerosis, renal fibrosis and oxidative stress. Administration of low-dose hydralazine to obese mothers during gestation reduced renal global DNA methylation and renal fibrotic markers in week 32 offspring.

CONCLUSION

Gestational hydralazine reduced renal global DNA methylation in offspring of obese mothers and attenuated maternal obesity-induced renal fibrosis. These data support the use of low-dose hydralazine as a demethylating agent to prevent CKD arising in offspring due to maternal HFD consumption.

DNA Methylation Sustains "Inflamed" Memory of Peripheral Immune Cells Aggravating Kidney Inflammatory Response in Chronic Kidney Disease

The incidence of chronic kidney disease (CKD) has rapidly increased in the past decades. A progressive loss of kidney function characterizes a part of CKD even with intensive supportive treatment. Irrespective of its etiology, CKD progression is generally accompanied with the development of chronic kidney inflammation that is pathologically featured by the low-grade but chronic activation of recruited immune cells. Cumulative evidence support that aberrant DNA methylation pattern of diverse peripheral immune cells, including T cells and monocytes, is closely associated with CKD development in many chronic disease settings. The change of DNA methylation profile can sustain for a long time and affect the future genes expression in the circulating immune cells even after they migrate from the circulation into the involved kidney. It is of clinical interest to reveal the underlying mechanism of how altered DNA methylation regulates the intensity and the time length of the inflammatory response in the recruited effector cells. We and others recently demonstrated that altered DNA methylation occurs in peripheral immune cells and profoundly contributes to CKD development in systemic chronic diseases, such as diabetes and hypertension. This review will summarize the current findings about the influence of aberrant DNA methylation on circulating immune cells and how it potentially determines the outcome of CKD.

Epigenetics-based therapeutics for myocardial fibrosis

Myocardial fibrosis (MF) is a reactive remodeling process in response to myocardial injury. It is mainly manifested by the proliferation of cardiac muscle fibroblasts and secreting extracellular matrix (ECM) proteins to replace damaged tissue. However, the excessive production and deposition of extracellular matrix, and the rising proportion of type I and type III collagen lead to pathological fibrotic remodeling, thereby facilitating the development of cardiac dysfunction and eventually causing heart failure with heightened mortality. Currently, the molecular mechanisms of MF are still not fully understood. With the development of epigenetics, it is found that epigenetics controls the transcription of pro-fibrotic genes in MF by DNA methylation, histone modification and noncoding RNAs. In this review, we summarize and discuss the research progress of the mechanisms underlying MF from the perspective of epigenetics, including the newest m6A modification and crosstalk between different epigenetics in MF. We also offer a succinct overview of promising molecules targeting epigenetic regulators, which may provide novel therapeutic strategies against MF.

Angiotensin II type 1a receptor loss ameliorates chronic tubulointerstitial damage after renal ischemia reperfusion

We investigate whether suppressing the activation of the angiotensin II type 1a receptor (AT1a) can ameliorate severe chronic tubulointerstitial damage (TID) after renal ischemia reperfusion (IR) using AT1a knockout homozygous (AT1a^−/−) male mice. To induce severe chronic TID after renal IR, unilateral renal ischemia was performed via clamping of the right renal pedicle in both AT1a^−/− and wild-type (AT1a^+/+) mice for 45 min. While marked renal atrophy and severe TID at 70 days postischemia was induced in the AT1a^+/+ mice, such a development was not provoked in the AT1a^−/− mice. Although the AT1a^+/+ mice were administered hydralazine to maintain the same systolic blood pressure (SBP) levels as the AT1a^−/− mice with lower SBP levels, hydralazine did not reproduce the renoprotective effects observed in the AT1a^−/− mice. Acute tubular injury at 3 days postischemia was similar between the AT1a^−/− mice and the AT1a^+/+ mice. From our investigations using IR kidneys at 3, 14, and 28 days postischemia, the multiple molecular mechanisms may be related to prevention of severe chronic TID postischemia in the AT1a^−/− mice. In conclusion, inactivation of the AT1 receptor may be useful in preventing the transition of acute kidney injury to chronic kidney disease.

Combination Hydralazine and Isosorbide Dinitrate in Dialysis-Dependent ESRD (HIDE): A Randomized, Placebo-Controlled, Pilot Trial

Background

Combination therapy with isosorbide dinitrate (ISD) and hydralazine (HY) reduces heart failure mortality. The safety and tolerability in individuals requiring maintenance hemodialysis (HD) is unknown.

Methods

Single-center, randomized, placebo-controlled, double-blind pilot trial to explore safety and tolerability of ISD/HY in maintenance HD. Participants were randomized to placebo or combination ISD/HY. Dose was escalated over 3 weeks from ISD 10 mg/HY 10 mg to ISD 40 mg/HY 75 mg three times per day with the maximum tolerated dose maintained for the subsequent 21 weeks. Primary endpoints included adverse events, adverse events precluding further treatment with study medication, serious hypotension (i.e., requiring hospitalization or emergency room visit), and recurrent intra-dialytic hypotension. Efficacy signals included change in mitral annular E' velocity by tissue Doppler echocardiography and change in left ventricular coronary flow reserve on positron emission tomography.

Results

A total of 17 individuals were randomized to ISD/HY (N=7) or placebo (N=10). All participants assigned to ISD/HY completed dose escalation to 40/75 mg, but dose reductions were required in two participants. No participants discontinued therapy. There were no serious hypotension events. Recurrent intradialytic hypotension was less frequent with ISD/HY (0.47 events/patient-year) than placebo (1.83 events/patient-year, P=0.04). In contrast, nausea (ISD/HY, 1.90 events/patient-year; placebo, 0.50 events/patient-year, P=0.03) was significantly more frequent, and headache and diarrhea were numerically but not significantly more frequent with ISD/HY. Adverse events were more frequent with ISD/HY (11.4 events/patient-year) than placebo (6.31 events/patient-year). We did not detect between-group differences in the change in E' (P=0.34); ISD/HY showed a mean increase of 0.6 cm/s (SD 1.1), and placebo showed a mean decrease of 0.04 cm/s (SD 0.9). Changes in coronary flow reserve were minimal, -0.3 (0.2) with ISD/HY and -0.03 (0.5) in the placebo group, P=0.19.

Conclusions

ISD/HY appears to be well tolerated in patients being treated with maintenance HD, but headache and gastrointestinal side effects occur more frequently with ISD/HY compared with placebo.

Hydrogen sulfide attenuates renal fibrosis by inducing TET-dependent DNA demethylation on Klotho promoter

Hypoxia is a key pathogenetic characteristic of chronic kidney disease (CKD). Klotho has renoprotective effect and its expression is commonly suppressed in CKD patients. We showed that chronic hypoxia in unilateral ureteral obstruction model mice is associated with renal Klotho promoter methylation and expression silencing. Administration of low-dose of sodium hydrosulfide (NaHS) effectively ameliorated renal tubulointerstitial fibrosis in the mouse model by demethylating Klotho promoter and restoring its expression. Mechanistically, hypoxia microenvironment in CKD reduced cellular oxygen availability and Fe²⁺ concentration, and led to impaired activity of ten-eleven translocation (TET), which is critical in maintaining Klotho promoter demethylation status. NaHS treatment greatly improved hypoxia condition, restored TET activity, reversed DNA methylation, and thus, increased Klotho expression. Our results strongly suggested that correcting hypoxia condition to restore TET activity could be a promising therapeutic strategy against CKD.

Phenylenediamine-Based Carbon Nanodots Alleviate Acute Kidney Injury via Preferential Renal Accumulation and Antioxidant Capacity

As a reactive oxygen species (ROS)-promoted disease, acute kidney injury (AKI) is associated with high mortality and morbidity, but no effective pharmacological treatment is available. Kidney-targeted and ROS-reactive antioxidants are in urgent demand for AKI treatment. A promising nanotechnology-based strategy for targeting renal tubules offers new perspectives for AKI treatment but remains challenging because of the glomerular filtration barrier, which requires ultrasmall-sized therapeutics for penetration and filtration. Here, we fabricated four potential antioxidative carbon nanodots (CNDs) with ultrasmall size. After balancing the antioxidant properties and biocompatibility, m-phenylenediamine-based CNDs (PDA-CNDs) were chosen for further research. PDA-CNDs demonstrated remarkable antioxidant properties for scavenging multiple toxic free radicals, enabling efficient protection of cells under various oxidative stresses in vitro. Moreover, fluorescence imaging revealed that PDA-CNDs preferentially accumulated in the injured kidney of mice with ischemia-reperfusion (IR)-induced AKI. Blood renal function tests and kidney tissue staining revealed the therapeutic efficacy of PDA-CNDs for AKI in both the murine IR-induced AKI model and cisplatin-induced AKI model. Collectively, this is the first study revealing that specific rationally designed CNDs could be a promising pharmacological treatment for AKI induced by ROS.

Upregulated miR-101 inhibits acute kidney injury-chronic kidney disease transition by regulating epithelial-mesenchymal transition

Acute kidney injury (AKI) is an independent risk factor for chronic kidney disease (CKD). However, the role and mechanism of microRNA (miRNA, miR) in AKI-CKD transition are elusive. In this study, a murine model of renal ischemia/reperfusion was established to investigate the repairing effect and mechanism of miR-101a-3p on renal injury. The pathological damage of renal tissue was observed by hematoxylin and eosin and Masson staining. The levels of miR-101, profibrotic cytokines, and epithelial-mesenchymal transition (EMT) markers were analyzed using Western blotting, real-time polymerase chain reaction, and/or immunofluorescence. MiR-101 overexpression caused the downregulation of α-smooth muscle actin, collagen-1, and vimentin, as well as upregulation of E-cadherin, thereby alleviating the degree of renal tissue damage. MiR-101 overexpression mitigated hypoxic HK-2 cell damage. Collagen, type X, alpha 1 and transforming growth factor β receptor 1 levels were downregulated in hypoxic cells transfected with miR-101 mimic. Our study indicates that miR-101 is an anti-EMT miRNA, which provides a novel therapeutic strategy for AKI-CKD transition.

Ten-eleven translocation methyl-cytosine dioxygenase 2 deficiency exacerbates renal ischemia-reperfusion injury

BACKGROUND

Ten-eleven translocation (Tet) methyl-cytosine dioxygenases (including Tet1/2/3)-mediated 5mC oxidation and DNA demethylation play important roles in embryonic development and adult tissue homeostasis. The expression of Tet2 and Tet3 genes are relatively abundant in the adult murine kidneys while Tet1 gene is expressed at a low level. Although Tet3 has been shown to suppress kidney fibrosis, the role of Tet2 in kidney physiology as well as renal ischemia-reperfusion (IR) injury is still largely unknown.

RESULTS

Tet2^-/- mice displayed normal kidney morphology and renal function as WT mice while the expression of genes associated with tight junction and adherens junction was impaired. At 24 h post-renal IR, Tet2^-/- mice showed higher SCr and BUN levels, more severe tubular damage, and elevated expression of Kim1 and Ngal genes in the kidney in comparison with WT mice. Moreover, the transcriptomic analysis revealed augmented inflammatory response in the kidneys of Tet2^-/- mice.

CONCLUSIONS

Tet2 is dispensable for kidney development and function at baseline condition while protects against renal IR injury possibly through repressing inflammatory response. Our findings suggest that Tet2 may be a potential target for the intervention of IR-induced acute kidney injury (AKI).

N6-methyladenosine (m6A) methylation in ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is common during surgery and often results in organ dysfunction. The mechanisms of I/R injury are complex, diverse, and not well understood. RNA methylation is a novel epigenetic modification that is involved in the regulation of various biological processes, such as immunity, response to DNA damage, tumorigenesis, metastasis, stem cell renewal, fat differentiation, circadian rhythms, cell development and differentiation, and cell division. Research on RNA modifications, specifically N6-methyladenosine (m6A), have confirmed that they are involved in the regulation of organ I/R injury. In this review, we summarized current understanding of the regulatory roles and significance of m6A RNA methylation in I/R injury in different organs.

High-molecular weight hyaluronan attenuates tubulointerstitial scarring in kidney injury

Renal fibrosis features exaggerated inflammation, extracellular matrix (ECM) deposition, and peritubular capillary loss. We previously showed that IL-10 stimulates high-molecular weight hyaluronan (HMW-HA) expression by fibroblasts, and we hypothesize that HMW-HA attenuates renal fibrosis by reducing inflammation and ECM remodeling. We studied the effects of IL-10 overexpression on HA production and scarring in mouse models of unilateral ureteral obstruction (UUO) and ischemia/reperfusion (I/R) to investigate whether IL-10 antifibrotic effects are HA dependent. C57BL/6J mice were fed with the HA synthesis inhibitor, 4-methylumbelliferone (4-MU), before UUO. We observed that in vivo injury increased intratubular spaces, ECM deposition, and HA expression at day 7 and onward. IL-10 overexpression reduced renal fibrosis in both models, promoted HMW-HA synthesis and stability in UUO, and regulated cell proliferation in I/R. 4-MU inhibited IL-10-driven antifibrotic effects, indicating that HMW-HA is necessary for cytokine-mediated reduction of fibrosis. We also found that IL-10 induces in vitro HMW-HA production by renal fibroblasts via STAT3-dependent upregulation of HA synthase 2. We propose that IL-10-induced HMW-HA synthesis plays cytoprotective and antifibrotic roles in kidney injury, thereby revealing an effective strategy to attenuate renal fibrosis in obstructive and ischemic pathologies.

Hydralazine Sensitizes to the Antifibrotic Effect of 5-Aza-2'-deoxycytidine in Hepatic Stellate Cells

BACKGROUND

Hepatic stellate cell (HSC) activation is essential for the development of liver fibrosis. Epigenetic machinery, such as DNA methylation, is largely involved in the regulation of gene expression during HSC activation. Although the pharmacological DNA demethylation of HSC using 5-aza-2'-deoxycytidine (5-aza-dC) yielded an antifibrotic effect, this drug has been reported to induce excessive cytotoxicity at a high dose. Hydralazine (HDZ), an antihypertensive agent, also exhibits non-nucleoside demethylating activity. However, the effect of HDZ on HSC activation remains unclear. In this study, we performed a combined treatment with 5-aza-dC and HDZ to obtain an enhanced antifibrotic effect with lower cytotoxicity.

METHODS

HSC-T6 cells were used as a rat HSC cell line in this study. The cells were cultivated together with 1 µM 5-Aza-dC and/or 10 µg/mL of HDZ, which were refreshed every 24 h until the 96 h treatment ended. Cell proliferation was measured using the WST-1 assay. The mRNA expression levels of peptidylprolyl isomerase A (Ppia), an internal control gene, collagen type I alpha 1 (Cola1), RAS protein activator like 1 (Rasal1), and phosphatase and tensin homolog deleted from chromosome 10 (Pten) were analyzed using quantitative reverse transcription polymerase chain reaction.

RESULTS

The percentage cell viability with 5-aza-dC, HDZ, and combined treatment vs. the vehicle-only control was 101.4 ± 2.5, 95.2 ± 5.7, and 79.2 ± 0.7 (p < 0.01 for 5-aza-dC and p < 0.01 for HDZ), respectively, in the 48 h treatment, and 52.4 ± 5.6, 65.9 ± 3.4, and 29.9 ± 1.3 (p < 0.01 for 5-aza-dC and p < 0.01 for HDZ), respectively, in the 96 h treatment. 5-Aza-dC and the combined treatment markedly decreased Cola1 mRNA levels. Accordingly, the expression levels of Rasal1 and Pten, which are antifibrotic genes, were increased by treatment after the 5-aza-dC and combined treatments. Moreover, single treatment with HDZ did not affect the expression levels of Cola1, Rasal1, or Pten. These results suggest that HDZ sensitizes to the antifibrotic effect of 5-aza-dC in HSC-T6 cells. The molecular mechanism underlying the sensitization to the antifibrotic effect of 5-aza-dC by HDZ remains to be elucidated. The expression levels of rat equilibrative nucleoside transporter genes (rEnt1, rEnt2, and rEnt3) were not affected by HDZ in this study.

CONCLUSIONS

Further confirmation using primary HSCs and in vivo animal models is desirable, but combined treatment with 5-aza-dC and HDZ may be an effective therapy for liver fibrosis without severe adverse effects.

Vitamin B Supplementation and Nutritional Intake of Methyl Donors in Patients with Chronic Kidney Disease: A Critical Review of the Impact on Epigenetic Machinery

Cardiovascular morbidity and mortality are several-fold higher in patients with advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) than in the general population. Hyperhomocysteinemia has undoubtedly a central role in such a prominent cardiovascular burden. The levels of homocysteine are regulated by methyl donors (folate, methionine, choline, betaine), and cofactors (vitamin B6, vitamin B12,). Uremia-induced hyperhomocysteinemia has as its main targets DNA methyltransferases, and this leads to an altered epigenetic control of genes regulated through methylation. In renal patients, the epigenetic landscape is strictly correlated with the uremic phenotype and dependent on dietary intake of micronutrients, inflammation, gut microbiome, inflammatory status, oxidative stress, and lifestyle habits. All these factors are key contributors in methylome maintenance and in the modulation of gene transcription through DNA hypo- or hypermethylation in CKD. This is an overview of the epigenetic changes related to DNA methylation in patients with advanced CKD and ESRD. We explored the currently available data on the molecular dysregulations resulting from altered gene expression in uremia. Special attention was paid to the efficacy of B-vitamins supplementation and dietary intake of methyl donors on homocysteine lowering and cardiovascular protection.