Transcription Factors and Epigenetic Modulation: Its Therapeutic Implication in Chronic Kidney Disease

Targeting epigenetic and posttranslational modifications regulating ferroptosis for the treatment of diseases

Ferroptosis, a unique modality of cell death with mechanistic and morphological differences from other cell death modes, plays a pivotal role in regulating tumorigenesis and offers a new opportunity for modulating anticancer drug resistance. Aberrant epigenetic modifications and posttranslational modifications (PTMs) promote anticancer drug resistance, cancer progression, and metastasis. Accumulating studies indicate that epigenetic modifications can transcriptionally and translationally determine cancer cell vulnerability to ferroptosis and that ferroptosis functions as a driver in nervous system diseases (NSDs), cardiovascular diseases (CVDs), liver diseases, lung diseases, and kidney diseases. In this review, we first summarize the core molecular mechanisms of ferroptosis. Then, the roles of epigenetic processes, including histone PTMs, DNA methylation, and noncoding RNA regulation and PTMs, such as phosphorylation, ubiquitination, SUMOylation, acetylation, methylation, and ADP-ribosylation, are concisely discussed. The roles of epigenetic modifications and PTMs in ferroptosis regulation in the genesis of diseases, including cancers, NSD, CVDs, liver diseases, lung diseases, and kidney diseases, as well as the application of epigenetic and PTM modulators in the therapy of these diseases, are then discussed in detail. Elucidating the mechanisms of ferroptosis regulation mediated by epigenetic modifications and PTMs in cancer and other diseases will facilitate the development of promising combination therapeutic regimens containing epigenetic or PTM-targeting agents and ferroptosis inducers that can be used to overcome chemotherapeutic resistance in cancer and could be used to prevent other diseases. In addition, these mechanisms highlight potential therapeutic approaches to overcome chemoresistance in cancer or halt the genesis of other diseases.

Transcriptional Signatures and Network-Based Approaches Identified Master Regulators Transcription Factors Involved in Experimental Periodontitis Pathogenesis

Periodontitis is a chronic inflammatory disease characterized by the progressive and irreversible destruction of the periodontium. Its aetiopathogenesis lies in the constant challenge of the dysbiotic biofilm, which triggers a deregulated immune response responsible for the disease phenotype. Although the molecular mechanisms underlying periodontitis have been extensively studied, the regulatory mechanisms at the transcriptional level remain unclear. To generate transcriptomic data, we performed RNA shotgun sequencing of the oral mucosa of periodontitis-affected mice. Since genes are not expressed in isolation during pathological processes, we disclose here the complete repertoire of differentially expressed genes (DEG) and co-expressed modules to build Gene Regulatory Networks (GRNs) and identify the Master Transcriptional Regulators of periodontitis. The transcriptional changes revealed 366 protein-coding genes and 42 non-coding genes differentially expressed and enriched in the immune response. Furthermore, we found 13 co-expression modules with different representation degrees and gene expression levels. Our GRN comprises genes from 12 gene clusters, 166 nodes, of which 33 encode Transcription Factors, and 201 connections. Finally, using these strategies, 26 master regulators of periodontitis were identified. In conclusion, combining the transcriptomic analyses with the regulatory network construction represents a powerful and efficient strategy for identifying potential periodontitis-therapeutic targets.

Paeoniflorin suppresses kidney inflammation by regulating macrophage polarization via KLF4-mediated mitophagy

BACKGROUND

Macrophages M1 polarization involved in the process of renal inflammatory injury, is a well-established hallmark of chronic kidney disease (CKD). Paeoniflorin (PF), a water-soluble monoterpene glycoside extracted from Paeonia lactiflora, revealed renal anti-inflammatory activities in our previous study. However, the potential molecular mechanism of PF on CKD remains unknown.

PURPOSE

The present study aims to investigate the regulation of PF on macrophage polarization in CKD.

METHODS

A CKD model was established by cationic bovine serum albumin and a murine macrophage cell line RAW264.7 induced with lipopolysaccharide (LPS) were used to clarify the underlying mechanisms of PF in CKD.

RESULTS

Results showed that PF exhibited favorable protective effects on CKD model mice by promoting renal function, ameliorating renal pathological injury and podocyte damage. Furthermore, PF inhibited the infiltration of M1 macrophage marker CD68 and iNOS in kidney tissue, but increased the proportion of M2 macrophage marker CD206. In RAW264.7 cells stimulated with LPS, the levels of cytokines including IL-6, IL-1β, TNF-α, MCP-1 were lessened under PF treatment, while the levels of Arg1, Fizz1, IL-10 and Ym-1 were augmented. These results indicated that PF promoted macrophage polarization from M1 to M2 in vivo and in vitro. More importantly, PF repaired the damaged mitochondria through increasing mitochondrial membrane potential and reducing ROS accumulation. The mitophagy-related proteins PINK1, Parkin, Bnip3, P62 and LC3 were up-regulated by PF, accompanied by the incremental expressions of Krüppel-like transcription factor 4 (KLF4). Moreover, the promotion of mitophagy and inhibition of M1 macrophage polarization owing to PF were reversed by mitophagy inhibitor Mdivi-1 or silencing KLF4.

CONCLUSION

Overall, PF suppressed renal inflammation by promoting macrophage polarization from M1 to M2 and inducing mitophagy via regulating KLF4. It is expected to provide a new strategy for exploring the effects of PF in treating CKD.

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.

Krϋppel-like factors (KLFs) in renal physiology and disease

Dysregulated Krϋppel-like factor (KLF) gene expression appears in many disease-associated pathologies. In this review, we discuss physiological functions of KLFs in the kidney with a focus on potential pharmacological modulation/therapeutic applications of these KLF proteins. KLF2 is critical to maintaining endothelial barrier integrity and preventing gap formations and in prevention of glomerular endothelial cell and podocyte damage in diabetic mice. KLF4 is renoprotective in the setting of AKI and is a critical regulator of proteinuria in mice and humans. KLF6 expression in podocytes preserves mitochondrial function and prevents podocyte apoptosis, while KLF5 expression prevents podocyte apoptosis by blockade of ERK/p38 MAPK pathways. KLF15 is a critical regulator of podocyte differentiation and is protective against podocyte injury. Loss of KLF4 and KLF15 promotes renal fibrosis, while fibrotic kidneys have increased KLF5 and KLF6 expression. For therapeutic modulation of KLFs, continued screening of small molecules will promote drug discoveries targeting KLF proteins.

Organ memory: a key principle for understanding the pathophysiology of hypertension and other non-communicable diseases

In recent years, several post-interventional analyses of large-scale randomized controlled clinical trials have given us a new concept regarding the risk management of hypertension and cardiovascular diseases. The beneficial effects of intensive treatments were extended even after the interventions ended. This phenomenon is known as "metabolic memory" or "legacy effect", and we recognized its clinical significance. A certain level of evidence in human and animal studies employing organ transplantation techniques has indicated that this type of "memory" resides in each organ and could be transferrable, erasable, and rewritable, which is similar to neuronal and immune "memory". In this review, we define this memory as "organ memory" and summarize the current picture and future direction of this concept. "Organ memory" can be observed in many clinical settings, including in the control of hypertension, diabetes mellitus, and dyslipidemia. Several intensive treatments were demonstrated to have the potential to rewrite "organ memory", leading to the curability of targeted diseases. "Organ memory" is the engraved phenotype of altered organ responsiveness acquired by a time-dependent accumulation of organ stress responses. Not only is the epigenetic change of key genes involved in the formation of "organ memory" but the alteration of multiple factors, including low molecular weight energy metabolites, immune mediators, and tissue structures, is involved as well. These factors intercommunicate during every stress response and carry out incessant remodeling in a certain direction in a spiral fashion through positive feedback mechanisms. Future studies should be directed toward the identification of the core unit of "organ memory" and its manipulation.

DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease

Chronic kidney disease (CKD) is a global epidemic, and its major risk factors include obesity and type 2 diabetes. Obesity not only promotes metabolic dysregulation and the development of diabetic kidney disease but also may independently lead to CKD by a variety of mechanisms, including endocrine and metabolic dysfunction, inflammation, oxidative stress, altered renal hemodynamics, and lipotoxicity. Deleterious renal effects of obesity can also be transmitted from one generation to the next, and it is increasingly recognized that offspring of obese mothers are predisposed to CKD. Epigenetic modifications are changes that regulate gene expression without altering the DNA sequence. Of these, DNA methylation is the most studied. Epigenetic imprints, particularly DNA methylation, are laid down during critical periods of fetal development, and they may provide a mechanism by which maternal-fetal transmission of chronic disease occurs. Our current review explores the evidence for the role of DNA methylation in the development of CKD, diabetic kidney disease, diabetes, and obesity. DNA methylation has been implicated in renal fibrosis-the final pathophysiologic pathway in the development of end-stage kidney disease-which supports the notion that demethylating agents may play a potential therapeutic role in preventing development and progression of CKD.-Larkin, B. P., Glastras, S. J., Chen, H., Pollock, C. A., Saad, S. DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease.

The Role of Krüppel-like Factor 4 in Renal Fibrosis

Chronic kidney disease (CKD) caused by renal fibrosis is an important public health concern. It is therefore necessary to understand the molecular pathogenesis of renal fibrosis in order to develop novel therapeutic strategies. KLF4 is the most extensively studied factor among the various members of the Krüppel-like factor (KLF) family of zinc finger-containing transcription factors. Many studies have demonstrated that KLF4 inhibits the activation of myofibroblasts and exerts an inhibitory effect on fibrosis. However, other studies have indicated that KLF4 may promote renal fibrosis. These controversial results suggest that KLF4 may be crucially involved in the development of renal fibrosis, although the underlying mechanism(s) remain unclear. Here, we summarize the recent progress made in understanding the role of KLF4 in renal fibrosis. Together, these findings suggest that KLF4 may participate in the development of renal fibrosis, but that its inhibition of fibrosis is greater than its promotion of the condition, which suggests that KLF4 may serve as a novel therapeutic target for renal fibrosis.