FIH-1-modulated HIF-1α C-TAD promotes acute kidney injury to chronic kidney disease progression via regulating KLF5 signaling

Exploring the Functionality of the Krüppel-like Factors in Kidney Development, Metabolism, and Diseases

The kidneys contribute to the overall health of an organism by maintaining systemic homeostasis. This process involves various biological mechanisms, in which the Krüppel-like factors (KLFs), a family of transcription factors, are essential for regulating development, differentiation, proliferation, and cellular apoptosis. They also play a role in the metabolic regulation of essential nutrients, such as glucose and lipids. The dysregulation of these transcription factors is associated with the development of various pathologies, which can ultimately lead to renal fibrosis, severely compromising kidney function. In this context, the present article provides a comprehensive review of the existing literature, offering an enriching analysis of the findings related to the role of KLFs in nephrology, while also highlighting their potential therapeutic role in the treatment of renal diseases.

Sanqi oral solution ameliorates renal fibrosis by suppressing fibroblast activation via HIF-1α/PKM2/glycolysis pathway in chronic kidney disease

ETHNOPHARMACOLOGICAL RELEVANCE

Sanqi oral solution (SQ) is a traditional Chinese patent medicine, widely used to treat chronic kidney diseases (CKD) in the clinic in China. Previous studies have confirmed its anti-renal fibrosis effect, but the specific pharmacological mechanism is still unclear.

AIM OF THE STUDY

Focusing on energy metabolism in fibroblasts, the renoprotective mechanism of SQ was investigated in vitro and in vivo.

METHODS

Firstly, the fingerprint of SQ was constructed and its elementary chemical composition was analyzed. In the 5/6Nx rats experiment, the efficacy of SQ on the kidney was evaluated by detecting serum and urine biochemical indexes and pathological staining of renal tissues. Lactic acid and pyruvic acid levels in serum and renal tissues were detected. PCNA protein expression in kidney tissue was detected by immunofluorescence assay and Western blot. Expression levels of HIF-1α, PKM2 and HK2 were determined by immunohistochemistry, Western blot or RT-qPCR assay. In addition, the effect of SQ intervention on cell proliferation and glycolysis was evaluated in TGF-β1-induced NRK-49F cells, and the role of SQ exposure and HIF-1α/PKM2/glycolysis pathway were further investigated by silencing and overexpressing HIF-1α gene in NRK-49F cells.

RESULTS

In 5/6 Nx rats, SQ effectively improved renal function and treated renal injury. It reduced the levels of lactic acid and pyruvic acid in kidney homogenates from CKD rats and decreased the expression levels of HIF-1α, PKM2, HK2, α-SMA, vimentin, collagen I and PCNA in kidney tissues. Similar results were observed in vitro. SQ inhibited NRK-49F cell proliferation, glycolysis and the expression levels of HIF-1α, PKM2 induced by TGF-β1. Furthermore, we established NRK-49F cells transfected with siRNA or pDNA to silence or overexpress the HIF-1α gene. Overexpression of HIF-1α promoted cellular secretion of lactic acid and pyruvic acid in TGF-β1-induced NRK-49F cells, however, this change was reversed by intervention with SQ or silencing the HIF-1α gene. Overexpression of HIF-1α can further induce increased PKM2 expression, while SQ intervention can reduce PKM2 expression. Moreover, PKM2 expression was also inhibited after silencing HIF-1α gene, and SQ was not effective even when given.

CONCLUSION

The mechanism of action of SQ was explored from the perspective of energy metabolism, and it was found to regulate PKM2-activated glycolysis, inhibit fibroblast activation, and further ameliorate renal fibrosis in CKD by targeting HIF-1α.

HDAC6 promotes inflammation in lupus nephritis mice by regulating transcription factors MAFF and KLF5 in renal fibrosis

AIM

This study explored the effect and mechanism of MAFF and HDAC6 on renal fibrosis and inflammation in lupus nephritis (LN).

METHODS

IL-33 treated renal epithelial cells and MRL/lpr mice were respectively used for in vitro and in vivo experiments. The expressions of HDAC6, MAFF, and KLF5 were measured in cells and renal tissues. Before and after cell transfection, the morphological changes in renal tissues were observed using Hematoxylin and eosin (H&E) and Masson staining. The proteinuria, serum creatinine (SCr), blood urea nitrogen (BUN), and double-stranded DNA (dsDNA) levels were detected by biochemical analysis. The expressions of fibrosis and inflammation related proteins (including α-SMA, Vimentin, IL-1β, IL-6, and TNF-α), p65, and iNOS were also detected. The relationship among MAFF, HDAC6, and KLF5 was determined by chromatin immunoprecipitation and dual luciferase reporter gene assay.

RESULTS

Renal tissues and cell models had elevated expressions of HDAC6 and KLF5, and decreased MAFF expression. HDAC6 suppression or MAFF overexpression led to suppression of proteinuria, SCr, BUN, and dsDNA levels, as well as attenuation of inflammatory infiltration and collagen deposition. HDAC6 can suppress MAFF expression via deacetylation to abolish its suppression of KLF5 expression, thus increasing KLF5 expression. In vivo and in vitro experiments showed the suppressive effect of HDAC6 suppression on renal fibrosis and inflammation can be abolished by KLF5 overexpression.

CONCLUSION

HDAC6 suppresses MAFF expression via deacetylation to elevate KLF5 expression, which consequently enhances fibrosis and inflammatory response in LN.

Investigating the regulatory mechanism of glucose metabolism by ubiquitin-like protein MNSFβ

BACKGROUND

Monoclonal nonspecific suppressor factor β (MNSFβ), a ubiquitously expressed member of the ubiquitin-like protein family, is associated with diverse cell regulatory functions. It has been implicated in glycolysis regulation and cell proliferation enhancement in the macrophage-like cell line Raw264.7. This study aims to show that HIF-1α regulates MNSFβ-mediated metabolic reprogramming.

METHODS AND RESULTS

In Raw264.7 cells, MNSFβ siRNA increased the oxygen consumption rate and reactive oxygen species (ROS) production but decreased ATP levels. Cells with MNSFβ knockdown showed a markedly increased ATP reduction rate upon the addition of oligomycin, a mitochondrial ATP synthase inhibitor. In addition, MNSFβ siRNA decreased the expression levels of mRNA and protein of HIF-1α-a regulator of glucose metabolism. Evaluation of the effect of MNSFβ on glucose metabolism in murine peritoneal macrophages revealed no changes in lactate production, glucose consumption, or ROS production.

CONCLUSION

MNSFβ affects both glycolysis and mitochondrial metabolism, suggesting HIF-1α involvement in the MNSFβ-regulated glucose metabolism in Raw264.7 cells.

Hypoxia-inducible factor in breast cancer: role and target for breast cancer treatment

Globally, breast cancer stands as the most prevalent form of cancer among women. The tumor microenvironment of breast cancer often exhibits hypoxia. Hypoxia-inducible factor 1-alpha, a transcription factor, is found to be overexpressed and activated in breast cancer, playing a pivotal role in the anoxic microenvironment by mediating a series of reactions. Hypoxia-inducible factor 1-alpha is involved in regulating downstream pathways and target genes, which are crucial in hypoxic conditions, including glycolysis, angiogenesis, and metastasis. These processes significantly contribute to breast cancer progression by managing cancer-related activities linked to tumor invasion, metastasis, immune evasion, and drug resistance, resulting in poor prognosis for patients. Consequently, there is a significant interest in Hypoxia-inducible factor 1-alpha as a potential target for cancer therapy. Presently, research on drugs targeting Hypoxia-inducible factor 1-alpha is predominantly in the preclinical phase, highlighting the need for an in-depth understanding of HIF-1α and its regulatory pathway. It is anticipated that the future will see the introduction of effective HIF-1α inhibitors into clinical trials, offering new hope for breast cancer patients. Therefore, this review focuses on the structure and function of HIF-1α, its role in advancing breast cancer, and strategies to combat HIF-1α-dependent drug resistance, underlining its therapeutic potential.

Hypoxia and renal fibrosis

Renal fibrosis is the final stage of most progressive kidney diseases. Chronic kidney disease (CKD) is associated with high comorbidity and mortality. Thus, preventing fibrosis and thereby preserving kidney function increases the quality of life and prolongs the survival of patients with CKD. Many processes such as inflammation or metabolic stress modulate the progression of kidney fibrosis. Hypoxia has also been implicated in the pathogenesis of renal fibrosis, and oxygen sensing in the kidney is of outstanding importance for the body. The dysregulation of oxygen sensing in the diseased kidney is best exemplified by the loss of stimulation of erythropoietin production from interstitial cells in the fibrotic kidney despite anemia. Furthermore, hypoxia is present in acute or chronic kidney diseases and may affect all cell types present in the kidney including tubular and glomerular cells as well as resident immune cells. Pro- and antifibrotic effects of the transcription factors hypoxia-inducible factors 1 and 2 have been described in a plethora of animal models of acute and chronic kidney diseases, but recent advances in sequencing technologies now allow for novel and deeper insights into the role of hypoxia and its cell type-specific effects on the progression of renal fibrosis, especially in humans. Here, we review existing literature on how hypoxia impacts the development and progression of renal fibrosis.

Knockdown of KLF5 ameliorates renal fibrosis in MRL/lpr mice via inhibition of MX1 transcription

OBJECTIVE

This study aims to elucidate the role of Kruppel-like factor (KLF5) and myxovirus resistance 1 (MX1) in the progression of renal fibrosis in lupus nephritis (LN).

METHODS

First, the expression of KLF5 and MX1 was assessed in the peripheral blood of LN patients and healthy participants. Next, the pathological changes in renal tissues were evaluated and compared in BALB/c and MRL/lpr mice, by detecting the expression of fibrosis marker proteins (transforming growth factor-β [TGF-β] and CTGF) and α-SMA, the content of urine protein, and the levels of serum creatinine, blood urea nitrogen, and serum double-stranded DNA antibody. In TGF-β1-induced HK-2 cells, the messenger RNA levels of KLF5 and MX1 were tested by qRT-PCR, and the protein expression of α-SMA, type I collagen (Col I), fibronectin (FN), and matrix metalloproteinase 9 (MMP9) was measured by western blot analysis. Moreover, the relationship between KLF5 and MX1 was predicted and verified.

RESULTS

In renal tissues of MRL/lpr mice and the peripheral blood of LN patients, KLF5 and MX1 were highly expressed. Pearson analysis revealed that KLF5 was positively correlated with MX1. Furthermore, KLF5 bound to MX1 promoter and promoted its transcription level. MRL/lpr mice showed substantial renal injury, accompanied by increased expression of α-SMA, TGF-β, CTGF, Col I, FN, and MMP9. Injection of sh-KLF5 or sh-MX1 alone in MRL/lpr mice reduced renal fibrosis in LN, while simultaneous injection of sh-KLF5 and ad-MX1 exacerbated renal injury and fibrosis. Furthermore, we obtained the same results in TGF-β1-induced HK-2 cells.

CONCLUSION

Knockdown of KLF5 alleviated renal fibrosis in LN through repressing the transcription of MX1.

Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Significance: The disturbance of the hypoxia response system is closely related to human diseases, because it is essential for the maintenance of homeostasis. Given the significant role of the hypoxia response system in human health, therapeutic applications targeting prolyl hydroxylase-hypoxia-inducible factor (HIF) signaling have been attempted. Thus, systemically reviewing the hypoxia response-based therapeutic strategies is of great significance. Recent Advances: Disturbance of the hypoxia response is a characteristic feature of various diseases. Targeting the hypoxia response system is, thus, a promising therapeutic strategy. Interestingly, several compounds and drugs are currently under clinical trials, and some have already been approved for use in the treatment of certain human diseases. Critical Issues: We summarize the molecular mechanisms of the hypoxia response system and address the potential therapeutic implications in kidney diseases. Given that the effects of hypoxia response in kidney diseases are likely to depend on the pathological context, specific cell types, and the differences in the activation pattern of HIF isoforms, the precise application is critical for the treatment of kidney diseases. Although HIF-PHIs (HIF-PHD inhibitors) have been proven to be effective and well tolerated in chronic kidney disease patients with anemia, the potential on-target consequence of HIF activation and some outstanding questions warrant further consideration. Future Direction: The mechanism of the hypoxia response system disturbance remains unclear. Elucidation of the molecular mechanism of hypoxia response and its precise effects on kidney diseases warrants clarification. Considering the complexity of the hypoxia response system and multiple biological processes controlled by HIF signaling, the development of more specific inhibitors is highly warranted. Antioxid. Redox Signal. 37, 936-955.

Calycosin attenuates renal ischemia/reperfusion injury by suppressing NF-κB mediated inflammation via PPARγ/EGR1 pathway

Renal ischemia reperfusion injury (IRI) is a leading and common cause of acute kidney injury (AKI), and inflammation is a critical factor in ischemic AKI progression. Calycosin (CAL), a major active component of Radix astragali, has been reported to have anti-inflammatory effect in multiple organs. However, whether CAL can alleviate renal IRI and its mechanism remain uncertain. In the present study, a renal IRI model is established by bilateral renal pedicles occlusion for 35 min in male C57BL/6 mice, and the effect of CAL on renal IRI is measured by serum creatinine and pathohistological assay. Hypoxia/reoxygenation (H/R) stimulated human renal tubular epithelial cells HK-2 were applied to explore the regulatory mechanisms of CAL. Luciferase reporter assay and molecular docking were applied to identify the CAL's target protein and pathway. In the mice with renal IRI, CAL dose dependently alleviated the renal injury and decreased nuclear factor kappa B (NF-κB) mediated inflammatory response. Bioinformatics analysis and experiments showed that early growth response 1 (EGR1) increased in mice with renal IRI and promoted NF-κB mediated inflammatory processes, and CAL dose-dependably reduced EGR1. Through JASPAR database and luciferase reporter assay, peroxisome proliferator-activated receptor γ (PPARγ) was predicted to be a transcription factor of EGR1 and repressed the expression of EGR1 in renal tubular epithelial cells. CAL could increase PPARγ in a dose dependent manner in mice with renal IRI and molecular docking predicted CAL could bind stably to PPARγ. In HK-2 cells after H/R, CAL increased PPARγ, decreased EGR1, and inhibited NF-κB mediated inflammatory response. However, PPARγ knockdown by siRNA transfection abrogated the anti-inflammation therapeutic effect of CAL. CAL produced a protective effect on renal IRI by attenuating NF-κB mediated inflammatory response via PPARγ/EGR1 pathway.

Macrophage‑derived exosomal miRNA‑155 promotes tubular injury in ischemia‑induced acute kidney injury

Tubule injury is a characteristic pathological feature of acute kidney injury (AKI) and determines the prognosis of kidney disease. However, the exact mechanism of tubule injury remains largely unclear. In the present study, the exact mechanism of tubule injury was investigated. Bilateral renal ischemia/reperfusion (I/R) injury (I/RI) was induced in mice and exosome secretion inhibitor GW4869 and miRNA-155 inhibitor were used. In addition, the exosomal microRNA (miR)-155-mediated cross-talk between macrophage and tubular cells was also investigated. It was determined that tubular injury was observed in an I/R-induced AKI model, which was closely associated with macrophage infiltration. Interestingly, blocking exosome production using GW4869 ameliorated tubular injury in I/R-induced AKI. Mechanistically, once released, activated macrophage-derived exosomal miR-155 was internalized by tubular cells, resulting in increased tubule injury through targeting of suppressor of cytokine signaling-1 (SOCS-1), a negative regulator of NF-κB signaling. In addition, a dual-luciferase reporter assay confirmed that SOCS-1 was the direct target of miR-155 in tubular cells. Notably, injection of these miR-155-enriched exosomes into renal parenchyma resulted in increased tubule injury in vivo. Thus, the present study demonstrated that exosomal miR-155 mediated the communication between activated macrophages and injured tubules, leading to progression of AKI, which not only provide novel insights into the pathophysiology of AKI but also offer a new therapeutic strategy for kidney diseases.

The role of hypoxia-inducible factor-1 alpha in multidrug-resistant breast cancer

Breast cancer is the most common cancer in women worldwide with increasing incidence. Significant therapeutics advances in the field of breast cancer have resulted in a growing number of treatment options, whereas de novo or acquired resistance is still a persistent clinical challenge. Drug resistance involves a variety of mechanisms, and hypoxia is one of the many causes. Hypoxia-inducible Factor-1 Alpha (HIF-1α) is a key transcription factor which can regulate the response of cells to hypoxia. HIF-1α can trigger anaerobic glycolysis of tumor cells, induce angiogenesis, promote the proliferation, invasion, and migration of tumor cells, and lead to multidrug resistance. This review mainly discusses the role of HIF-1α in the drug-resistant breast cancer and highlighted the potential of HIF-1α -targeted therapy.

MicroRNA-122-5p ameliorates tubular injury in diabetic nephropathy via FIH-1/HIF-1α pathway

Diabetes kidney disease (DKD) affects approximately one-third of diabetes patients, however, the specific molecular mechanism of DKD remains unclear, and there is still a lack of effective therapies. Here, we demonstrated a significant increase of microRNA-122-5p (miR-122-5p) in renal tubular cells in STZ induced diabetic nephropathy (DN) mice. Moreover, inhibition of miR-122-5p led to increased cell death and serve tubular injury and promoted DN progression following STZ treatment in mice, whereas supplementation of miR-122-5p mimic had kidney protective effects in this model. In addition, miR-122-5p suppressed the expression of factor inhibiting hypoxia-inducible factor-1 (FIH-1) in vitro models of DN. microRNA target reporter assay further verified FIH-1 as a direct target of miR-122-5p. Generally, FIH-1 inhibits the activity of HIF-1α. Our in vitro study further indicated that overexpression of HIF-1α by transfection of HIF-1α plasmid reduced tubular cell death, suggesting a protective role of HIF-1α in DN. Collectively, these findings may unveil a novel miR-122-5p/FIH-1/HIF-1α pathway which can attenuate the DN progression.

Changes in aging-induced kidney dysfunction in mice based on a metabolomics analysis

Kidney dysfunction is particularly important in systemic organ injuries caused by aging. Metabolomics are utilized in this study to explore the mechanism of kidney dysfunction during aging by the identification of metabolites and the characterization of metabolic pathways. We analyzed the serum biochemistry and kidney histopathology of male Kunming mice aged 3 months and 24 months and found that the aged mice had inflammatory lesions, aggravated fibrosis, and functional impairment. A high-resolution untargeted metabolomics analysis revealed that the endogenous metabolites in the kidneys and urine of the mice were significantly changed by 25 and 20 metabolites, respectively. A pathway analysis of these differential metabolites revealed six key signaling pathways, namely, D-glutamine and D-glutamate metabolism, purine metabolism, the citrate cycle [tricarboxylic acid (TCA) cycle], histidine metabolism, pyruvate metabolism, and glyoxylate and dicarboxylate metabolism. These pathways are involved in amino acid metabolism, carbohydrate metabolism, and nucleotide metabolism, and these can lead to immune regulation, inflammatory responses, oxidative stress damage, cellular dysfunction, and bioenergy disorders, and they are closely associated with aging and kidney insufficiency. We also screened nine types of sensitive metabolites in the urine as potential biomarkers of kidney dysfunction during the aging process to confirm their therapeutic targets in senior-induced kidney dysfunction and to improve the level of risk assessment for senile kidney injury.