SIRT7 orchestrates melanoma progression by simultaneously promoting cell survival and immune evasion via UPR activation

Xenotropic and polytropic retrovirus receptor 1 (XPR1) promotes progression of papillary thyroid carcinoma via the BRAF-ERK1/2-P53 signaling pathway

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Xenotropic and polytropic retrovirus receptor 1 (XPR1), identified as a cellular receptor, plays roles in many pathophysiological processes. However, the underlying function and molecular mechanisms of XPR1 in PTC remain unclear. Therefore, this study aimed to elucidate the role of XPR1 in the process of PTC and the potential mechanisms.

METHODS

RNA-sequencing was performed for gene differential expression analysis in PTC patients' tissues. Immunohistochemical assay, real-time PCR, and western blotting assay were used to determine the expression of XPR1, BRAF, and P53 in PTC tissues. The function of XPR1 on the progression of PTC was explored using in vitro and in vivo experiments. The molecular mechanism of XPR1 was investigated using gene silencing, ELISA, immunofluorescence, western blotting, and real-time PCR assays.

RESULTS

We found that XPR1 was markedly upregulated in PTC tissues compared to adjacent noncancerous tissues, suggesting that high expression of XPR1 could be correlated with poor patient disease-free survival in PTC. In addition, the expression of BRAF and P53 in PTC tissues was substantially higher than in adjacent noncancerous tissues. Silencing of XPR1 reduced the proliferation, migration, and invasion capacities of TPC-1 cells in vitro and effectively inhibited the tumorigenecity of PTC in vivo. More importantly, silencing of XPR1 in TPC-1 cells significantly decreased the expression of XPR1, BRAF, and P53 both in vitro and in vivo. Interestingly, we demonstrated that XPR1 may positively activate the BRAF-ERK-P53 signaling pathway, further promoting PTC progression.

CONCLUSION

The findings reveal a crucial role of XPR1 in PTC progression and prognosis via the BRAF-ERK1/2-P53 signaling pathway, providing potential therapeutic targets for treating PTC.

Sirtuin 7 Promotes Alcohol-Associated Liver Injury via Modulating Myeloid Cell Chemokine (C-C Motif) Ligand 2 Secretion through the NF-κB Signaling Pathway

The pathogenesis of alcohol-associated liver disease (ALD) involves ethanol-induced enhancement of gut permeability, bacterial products released from intestine and intrahepatic inflammation, and liver damage. Hepatic macrophages play a crucial role in mediating inflammatory response by alcohol. Sirtuin 7 (SIRT7), a NAD+-dependent type III histone deacetylase, is being recognized as a therapeutic target in various human diseases. Emerging evidence shows that SIRT7 participates in immune regulation, but whether it is involved in ALD remains elusive. In the present study, myeloid cell-specific Sirt7 knockout mice (Lyz2-Sirt7-/-) were used to show that knockout Sirt7 in myeloid cells significantly ameliorated alcohol-induced liver injury, inflammation, and cell infiltration, while only mildly affecting lipid metabolism pathways. Chemokine (C-C motif) ligand 2 (CCL2) was identified as the main target impaired by Sirt7 knockout after alcohol. In vitro studies confirmed that Sirt7 knockout impaired macrophages' ability of CCL2 secretion and monocyte recruiting, and exogenous CCL2 reversed this impairment. At the molecular level, knockout of Sirt7 significantly impaired lipopolysaccharide-induced p65 phosphorylation and nuclear localization. More importantly, the SIRT7 inhibitor 40569 sufficiently decreased alcohol-induced liver injury and hepatic inflammation via preventing CCL2 in vivo. The current data thus uncovered a previously undescribed role of myeloid SIRT7 in mediating ALD via promoting CCL2 secretion through the NF-κB signaling pathway. Targeting SIRT7 might offer novel mechanism-based therapeutic options for ALD.

Inhibition of SIRT4 promotes bladder cancer progression and immune escape via attenuating CD8+ T cells function

BACKGROUND

Bladder cancer (BCa) is one of the most common malignancies of the urinary system and is characterized by a high recurrence rate and significant mortality. Sirtuin 4 (SIRT4), a member of the NAD+-dependent deacetylase and ADP-ribosyltransferase family, is involved in regulating cellular metabolism, DNA repair, and longevity, potentially influencing tumor progression and immune escape. This study aimed to elucidate the role of SIRT4 in BCa.

METHODS

The correlation between the sirtuin family and immunotherapy sensitivity in BCa patients was analyzed via IMvigor210 data. The clinical significance and immunological role of SIRT4 across multiple cancer types were assessed by evaluating its associations with clinicopathologic features, prognosis, tumor mutation burden (TMB), microsatellite instability (MSI), immune cell infiltration, and immune response genes across 33 datasets from The Cancer Genome Atlas (TCGA). SIRT4 expression was confirmed in BCa tissues, and its functions were examined via proliferation and migration assays. CD8+ T cells were isolated from the peripheral blood of healthy individuals and activated with CD3 and CD28 antibodies and recombinant IL2. Coculture assays involving BCa cells and activated CD8+ T cells, alongside ELISA, were conducted to evaluate the immunological function of SIRT4.

RESULTS

SIRT4 was positively associated with the immunotherapy response of BCa patients on the basis of IMvigor210 data. Its expression was downregulated in 11 tumor types but upregulated in 3. SIRT4 was significantly correlated with tumor stage in 2 tumor types and showed varying associations with overall survival, progression-free survival, and disease-specific survival. Additionally, SIRT4 was correlated with TMB in 10 tumor types and with MSI in 8. GSEA indicated that SIRT4 was negatively associated with the immune response in 9 tumor types, excluding BCa. It was positively correlated with immune cell infiltration in 2 tumor types and negatively correlated in 6. The TCGA data revealed that SIRT4 was positively associated with activated NK cell infiltration but negatively associated with M1 macrophages, neutrophils, resting NK cells, and activated memory CD4 T cells. Enrichment analyses revealed positive correlations with various chemokines, immunoinhibitors, immunostimulators, lymphocytes, MHC molecules, and MHC receptors, suggesting that SIRT4 may enhance the immune response in BCa. Further experiments confirmed that SIRT4 was downregulated in BCa tissues compared with adjacent normal tissues. Inhibition of SIRT4 promoted BCa cell proliferation and migration, whereas knockdown of SIRT4 impaired the chemotaxis and tumor-killing ability of CD8+ T cells in the BCa tumor microenvironment.

CONCLUSIONS

In summary, SIRT4 inhibits the progression and immune escape of BCa, indicating its potential as a novel biomarker and immune checkpoint for immunotherapy.

Histone deacetylases in the regulation of cell death and survival mechanisms in resistant BRAF-mutant cancers

Small-molecule BRAF inhibitors (e.g., vemurafenib and dabrafenib) and MEK (MAPK/ERK) kinases inhibitors (e.g., trametinib) have distinctly improved the survival of patients suffering from BRAF-mutant cancers such as melanomas. However, the emergence of resistance to BRAF and MEK inhibitor-based melanoma therapy, as well as the reduced sensitivity of other BRAF-mutant cancers such as CRC, poses a considerable clinical problem. For instance, the reactivation of MAPK/ERK signaling hampering cell death induction mechanisms was responsible for BRAF inhibitor resistance, which can be correlated with distinct post-translational and epigenetic processes. Histone deacetylases (HDACs) are prominent epigenetic drug targets and some HDAC inhibitors have already been clinically approved for the therapy of various blood cancers. In addition, several HDACs were identified, which also play a crucial role in the drug resistance of BRAF-mutant cancers. Consequently, inhibition of HDACs was described as a promising approach to overcome resistance. This review summarizes the influence of HDACs (Zn2+-dependent HDACs and NAD+-dependent sirtuins) on BRAF-mutant cancers and BRAF inhibitor resistance based on upregulated survival mechanisms and the prevention of tumor cell death. Moreover, it outlines reasonable HDAC-based strategies to circumvent BRAF-associated resistance mechanisms based on downregulated cell death mechanisms.

Immune regulation and the tumor microenvironment in anti-PD-1/PDL-1 and anti-CTLA-4 therapies for cancer immune evasion: A bibliometric analysis

This study aims to conduct a bibliometric analysis, employing visualization tools to examine literature pertaining to tumor immune evasion related to anti-CTLA-4 and anti-PD-1/PD-L1 therapy from 1999 to 2022. A special emphasis is placed on the interplay between tumor microenvironment, signaling pathways, immune cells and immune evasion, with data sourced from the Web of Science core collection (WoSCC). Advanced tools, including VOSviewer, Citespace, and Scimago Graphica, were utilized to analyze various parameters, such as co-authorship/co-citation patterns, regional contributions, journal preferences, keyword co-occurrences, and significant citation bursts. Out of 4778 publications reviewed, there was a marked increase in research focusing on immune evasion, with bladder cancer being notably prominent. Geographically, China, the USA, and Japan were the leading contributors. Prestigious institutions like MD Anderson Cancer Center, Harvard Medical School, Fudan University, and Sun Yat Sen University emerged as major players. Renowned journals in this domain included Frontiers in Immunology, Cancers, and Frontiers in Oncology. Ehen LP and Wang W were identified as prolific authors on this topic, while Topalian SL stood out as one of the most cited. Research current situation is notably pivoting toward challenges like immunotherapy resistance and the intricate signaling pathways driving drug resistance. This bibliometric study seeks to provide a comprehensive overview of past and current research trends, emphasizing the potential role of tumor microenvironment, signaling pathways and immune cells in the context of immune checkpoint inhibitors (ICIs) and tumor immune evasion.

Mechanistic insights into SIRT7 and EZH2 regulation of cisplatin resistance in bladder cancer cells

Cisplatin (CDDP) resistance has been established to significantly impact Bladder Cancer (BCa) therapy. On the other hand, the crucial regulatory involvement of SIRT7 and EZH2 in bladder cancer development is well known. Herein, the collaborative regulatory roles and underlying mechanisms of SIRT7 and EZH2 in CDDP resistance in bladder cancer were explored. Immunohistochemistry (IHC) and Western Blot (WB) analyses were used to assess the expression levels of SIRT7/EZH2 and RND3 in bladder cancer tissues, normal ureteral epithelial cells, and bladder cancer cell lines. Furthermore, the impact of various treatments on of UMUC3 cell proliferation and CDDP sensitivity was assessed using CCK-8 assays, plate cloning assays, and flow cytometry analysis. Additionally, the levels of H3K18ac and H3K27me3 at the promoter region of the RND3 gene, the binding abilities of SIRT7 and EZH2, and the succinylation level of the EZH2 protein were examined using ChIP-qPCR assays, CO-IP assays, and IP assays, respectively. Moreover, in vivo experiments were conducted using a bladder cancer mouse model created by subcutaneously injecting UMUC3 cells into Balb/c nude mice. According to the results, SIRT7 correlated with the sensitivity of bladder cancer cells to both the platinum-based chemotherapy and CDDP. Specifically, SIRT7 could bind to the RND3 promoter, downregulating H3K18ac and RND3, ultimately leading to an increased CDDP sensitivity in UMUC3 cells. Furthermore, EZH2 siRNA could decrease H3K27me3 levels in the RND3 promoter, upregulating RND3. Overall, in the promoter region of the RND3 gene, SIRT7 upregulated H3K27me3 and EZH2 downregulated H3K18ac, leading to a decline in RND3 expression and CDDP sensitivity in bladder cancer cells. Additionally, SIRT7 reduced the succinylation of the EZH2 protein resulting in an EZH2-mediated RND3 downregulation. Therefore, targeting SIRT7 and EZH2 could be a viable approach to enhancing CDDP efficacy in bladder cancer treatment.

Bombyx mori UFBP1 regulates apoptosis and promotes BmNPV proliferation by affecting the expression of ER chaperone BmBIP

Ubiquitin-fold modifier 1 (UFM1) is attached to protein substrates through the sequential activity of an E1 (UBA5) - E2 (UFC1) - E3 (UFL1) cascade. UFBP1 is a conserved UFL1-interacting protein in mammals. However, to date, no study has been conducted on UFBP1 in silkworm. In this study, we identified a UFBP1 ortholog in the B. mori genome. Spatiotemporal expression profiles showed that BmUFBP1 expression was high in the midgut and fatbody, and at the moth stage. BmUFBP1 knockdown inhibited ER chaperone BmBIP expression and BmNPV proliferation, while BmUFBP1 overexpression increased BmNPV proliferation, and BmBIP rescued BmUFBP1-regulated BmNPV proliferation. Mechanistically, Apoptosis and ATF6 signaling are involved in BmUFBP1-regulated BmBIP expression and BmNPV proliferation. These results suggest that BmUFBP1 facilitates BmNPV proliferation via ATF6-BIP signaling, and provide a potential molecular target for BmNPV prevention and silkworm breeding.

Exercise-regulated lipolysis: Its role and mechanism in health and diseases

Exercise has received considerable attention because of its importance not just in regulating physiological function, but also in ameliorating multiple pathological processes. Among these processes, lipolysis may play an important role in exercise-induced benefits. It is generally accepted that active lipolysis contributes to breakdown of fats, leading to the release of free fatty acids (FFAs) that serve as an energy source for muscles and other tissues during exercise. However, the significance of lipolysis in the context of exercise has not been fully understood. This review comprehensively outlines the potential regulatory mechanisms by which exercise stimulates lipolysis. The potential roles of exercise-mediated lipolysis in various physiological and pathological processes are also summarized. Additionally, we also discussed the potential non-classical effects of key lipolytic effectors induced by exercise. This will enhance our understanding of how exercise improves lipolytic function to bring about beneficial effects, offering new insights into potential therapeutic avenues for promoting health and alleviating diseases.

IRE1β evolves to be a guardian of respiratory and gastrointestinal mucosa

Inositol-requiring enzyme 1 (IRE1), a mediator of the unfolded protein response, shows the highest degree of evolutionary conservation. Vertebrates express two IRE1 paralogs: IRE1α, which is universally expressed and IRE1β, which shows specific expression within mucus secreted cells in respiratory and gastrointestinal tracts. The biological properties and regulation of the two IRE1 duplicates show evolutionary differences. As recently suggested, IRE1β-deficient mice display impairment in secreted protein expression and mucosal homeostasis. Abnormal changes in IRE1β caused by external and internal factors can disrupt mucosal homeostasis and further lead to respiratory and gastrointestinal diseases. Here, we highlight the physiological functions of IRE1β in the respiratory and gastrointestinal tracts in response to environmental microbes, viruses, toxins, and food components.

SIRT7 protects against liver fibrosis by suppressing stellate cell activation via TGF-β/SMAD2/3 pathway

BACKGROUND

SIRT7 is a class III HDACs deacetylase which plays critical roles in various biological processes. Aberrant SIRT7 expression is associated with tumorigenesis and disease progression while role of SIRT7 in hepatic fibrosis remain elusive.

METHODS

SIRT7 expression was examined in fibrotic liver sample via WB and IHC. Myeloid cell-specific knockout (SIRT7MKO) mice were generated by crossing SIRT7flox/flox mice with LysM-Cre mice. Primary hepatic stellate cells (HSCs) was isolated to examine stellate cells activation. SIRT7 and SMAD2/3 interaction were analyzed by immunoprecipitation. SB525334 was used to prevent SMAD2/3 phosphorylation.

RESULTS

SIRT7 expression was decreased during chronic liver disease progression but was increased in liver cancer. IHC staining indicated that SIRT7 was primarily expressed in non-parenchymal cells in both fibrotic and cirrhotic liver. Knockout SIRT7 in myeloid cells resulted in significant elevation of serum ALT and liver fibrosis, but mildly affected hepatic inflammation after CCl4 treatment. We further observed significant elevation of elevation of stellate cell activation and SMAD2/3 activation in SIRT7MKO mice. By using primary HSCs and stellate cell line, we confirmed that SIRT7 interacted with SMAD2/3, induced its deacetylation and was critical in regulation of SMAD2/3 activation and stellate cell activation upon TGF-β stimulation. Pharmacological inhibition of SMAD2/3 reversed the hyperactivation of SIRT7MKO HSCs after TGF-β stimulation, and abolished stellate cell activation and liver fibrosis in SIRT7MKO mice.

CONCLUSION

Our findings revealed previously unidentified role of SIRT7 in regulating HSCs activation via modulating TGF-β/SMAD2/3 signaling pathway. Targeting SIRT7 might offer novel therapeutic option against liver fibrosis.

Unraveling the multifaceted role of SIRT7 and its therapeutic potential in human diseases

Sirtuins, as NAD+-dependent deacetylases, are widely found in eubacteria, archaea, and eukaryotes, and they play key roles in regulating cellular functions. Among these, SIRT7 stands out as a member discovered relatively late and studied less extensively. It is localized within the nucleus and displays enzymatic activity as an NAD+-dependent deacetylase, targeting a diverse array of acyl groups. The role of SIRT7 in important cellular processes like gene transcription, cellular metabolism, cellular stress responses, and DNA damage repair has been documented in a number of studies conducted recently. These studies have also highlighted SIRT7's strong correlation with human diseases like aging, cancer, neurological disorders, and cardiovascular diseases. In addition, a variety of inhibitors against SIRT7 have been reported, indicating that targeting SIRT7 may be a promising strategy for inhibiting tumor growth. The purpose of this review is to thoroughly look into the structure and function of SIRT7 and to explore its potential value in clinical applications, offering an essential reference for research in related domains.

The dark side of SIRT7

Sirtuin 7 (SIRT7) is a member of the sirtuin family and has emerged as a key player in numerous cellular processes. It exhibits various enzymatic activities and is predominantly localized in the nucleolus, playing a role in ribosomal RNA expression, DNA damage repair, stress response and chromatin compaction. Recent studies have revealed its involvement in diseases such as cancer, cardiovascular and bone diseases, and obesity. In cancer, SIRT7 has been found to be overexpressed in multiple types of cancer, including breast cancer, clear cell renal cell carcinoma, lung adenocarcinoma, prostate adenocarcinoma, hepatocellular carcinoma, and gastric cancer, among others. In general, cancer cells exploit SIRT7 to enhance cell growth and metabolism through ribosome biogenesis, adapt to stress conditions and exert epigenetic control over cancer-related genes. The aim of this review is to provide an in-depth understanding of the role of SIRT7 in cancer carcinogenesis, evolution and progression by elucidating the underlying molecular mechanisms. Emphasis is placed on unveiling the intricate molecular pathways through which SIRT7 exerts its effects on cancer cells. In addition, this review discusses the feasibility and challenges associated with the development of drugs that can modulate SIRT7 activity.

Strategically engineered Au(I) complexes for orchestrated tumor eradication via chemo-phototherapy and induced immunogenic cell death

Cancer is a significant cause of death around the world, and for many varieties, treatment is not successful. Therefore, there is a need for the development of innovative, efficacious, and precisely targeted treatments. Here, we develop a series of Au(I) complexes (1-4) through rational manipulation of ligand structures, thereby achieving tumor cell specific targeting and orchestrated tumor eradication via chemo-phototherapy and induced immunogenic cell death. A comprehensive exploration based on in vitro and in vivo female mice experimentation shows that complex 4 exhibits proficiency in specific tumor imaging, endoplasmic reticulum targeting, and has robust therapeutic capabilities. Mechanistic elucidation indicates that the anticancer effect derives from the synergistic actions of thioredoxin reductase inhibition, highly efficient reactive oxygen species production and immunogenic cell death. This work presents a report on a robust Au(I) complex integrating three therapeutic modalities within a singular system. The strategy presented in this work provides a valuable reference for the development of high-performance therapeutic agents.

SIRT7 promotes mitochondrial biogenesis to render the adaptive resistance to MAPK inhibition in melanoma

Melanoma, arising from the malignant transformation of melanocytes, stands as the most lethal type of skin cancer. While significant strides have been made in targeted therapy and immunotherapy, substantially enhancing therapeutic efficacy, the prognosis for melanoma patients remains unoptimistic. SIRT7, a nuclear-localized deacetylase, plays a pivotal role in maintaining cellular homeostasis and adapting to external stressors in melanoma, with its activity closely tied to intracellular nicotinamide adenine dinucleotide (NAD+). However, its involvement in adaptive resistance to targeted therapy remains unclear. Herein, we unveil that up-regulated SIRT7 promotes mitochondrial biogenesis to render the adaptive resistance to MAPK inhibition in melanoma. Initially, we observed a significant increase of SIRT7 expression in publicly available datasets following targeted therapy within a short duration. In consistent, we found elevated SIRT7 expression in melanoma cells subjected to BRAF or MEK inhibitors in vitro. The up-regulation of SIRT7 expression was also confirmed in xenograft tumors in mice after targeted therapy in vivo. Furthermore, we proved that SIRT7 deficiency led to decreased cell viability upon prolonged exposure to BRAF or MEK inhibitors, accompanied by an increase in cell apoptosis. Mechanistically, SIRT7 deficiency restrained the upregulation of genes associated with mitochondrial biogenesis and intracellular ATP levels in response to targeted therapy treatment in melanoma cells. Ultimately, we proved that SIRT7 deficieny could sensitize BRAF-mutant melanoma cells to MAPK inhibition targeted therapy in vivo. In conclusion, our findings underscore the role of SIRT7 in fostering adaptive resistance to targeted therapy through the facilitation of mitochondrial biogenesis. Targeting SIRT7 emerges as a promising strategy to overcome MAPK inhibitor adaptive resistance in melanoma.

SIRT7 promotes Hippo/YAP activation and cancer cell proliferation in hepatocellular carcinoma via suppressing MST1

Abnormal activation of the oncogene YAP in the Hippo pathway is a major feature in liver cancer and inactivation of MST1/2 has been shown to be responsible for the overactivation of YAP that led to tumorigenesis. However, mechanisms underlying MST1/2 dysregulation remain poorly understood. RNA-seq analysis and genome (KEGG) pathway enrichment analysis were used to identify genes and pathways that were regulated by SIRT7. qRT-PCR, ChIP, and luciferase assay were used to investigate transcriptional regulation. Mass spectrometry, co-immunoprecipitation and immunoprecipitation were used to exam protein-protein interaction and post-transcriptional modification. A xenograft mouse model was used to confirm the effect of SIRT7 and SIRT7 inhibitors on hepatocellular carcinoma (HCC) proliferation in vivo. We found that SIRT7 suppresses MST1 by both transcriptional regulation and post-transcriptional modification, which in turn promotes YAP nuclear localization and transcriptional activation in liver cancer. Mechanistically, we revealed that SIRT7 suppresses MST1 transcription by binding to the MST1 promoter and inducing H3K18 deacetylation in its promoter region. In addition, SIRT7 directly binds to and deacetylates MST1, which primes acetylation-dependent MST1 ubiquitination and protein degradation. In clinical samples, we confirmed a negative correlation between SIRT7 and MST1 protein levels, and high SIRT7 expression correlated with elevated YAP expression and nuclear localization. In addition, SIRT7 specific inhibitor 2800Z sufficiently inhibited HCC growth by disrupting the SIRT7/MST1/YAP axis. Our data thus revealed the previously undescribed function of SIRT7 in regulating the Hippo pathway in HCC and further proved that targeting SIRT7 might provide novel therapeutic options for the treatment of liver cancer.

SIRT7: a novel molecular target for personalized cancer treatment?

The Sirtuin family of NAD+-dependent enzymes assumes a pivotal role in orchestrating adaptive responses to environmental fluctuations and stress stimuli, operating at both genomic and metabolic levels. Within this family, SIRT7 emerges as a versatile player in tumorigenesis, displaying both pro-tumorigenic and tumor-suppressive functions in a context-dependent manner. While other sirtuins, such as SIRT1 and SIRT6, exhibit a similar dual role in cancer, SIRT7 stands out due to distinctive attributes that sharply distinguish it from other family members. Among these are a unique key role in regulation of nucleolar functions, a close functional relationship with RNA metabolism and processing -exceptional among sirtuins- and a complex multienzymatic nature, which provides a diverse range of molecular targets. This review offers a comprehensive overview of the current understanding of the role of SIRT7 in various malignancies, placing particular emphasis on the intricate molecular mechanisms employed by SIRT7 to either stimulate or counteract tumorigenesis. Additionally, it delves into the unique features of SIRT7, discussing their potential and specific implications in tumor initiation and progression, underscoring the promising avenue of targeting SIRT7 for the development of innovative anti-cancer therapies.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Sirtuins as Players in the Signal Transduction of Citrus Flavonoids

Sirtuins (SIRTs) belong to the family of nicotine adenine dinucleotide (NAD+)-dependent class III histone deacetylases, which come into play in the regulation of epigenetic processes through the deacetylation of histones and other substrates. The human genome encodes for seven homologs (SIRT1-7), which are localized into the nucleus, cytoplasm, and mitochondria, with different enzymatic activities and regulatory mechanisms. Indeed, SIRTs are involved in different physio-pathological processes responsible for the onset of several human illnesses, such as cardiovascular and neurodegenerative diseases, obesity and diabetes, age-related disorders, and cancer. Nowadays, it is well-known that Citrus fruits, typical of the Mediterranean diet, are an important source of bioactive compounds, such as polyphenols. Among these, flavonoids are recognized as potential agents endowed with a wide range of beneficial properties, including antioxidant, anti-inflammatory, hypolipidemic, and antitumoral ones. On these bases, we offer a comprehensive overview on biological effects exerted by Citrus flavonoids via targeting SIRTs, which acted as modulator of several signaling pathways. According to the reported studies, Citrus flavonoids appear to be promising SIRT modulators in many different pathologies, a role which might be potentially evaluated in future therapies, along with encouraging the study of those SIRT members which still lack proper evidence on their support.

DDX3X interacts with SIRT7 to promote PD-L1 expression to facilitate PDAC progression

Pancreatic ductal adenocarcinoma (PDAC) is recognized as the most aggressive and fatal malignancy. A previous study reported that PDAC patients who exhibit elevated levels of DDX3X have a poor prognosis and low overall survival rate. However, the underlying molecular mechanism remains unclear. This study aimed to investigate the specific roles of DDX3X in PDAC. Multiple bioinformatics analyses were used to evaluate DDX3X expression and its potential role in PDAC. In vitro and in vivo studies were performed to assess the effects of DDX3X on PDAC cell growth. Furthermore, Western blotting, quantitative PCR, immunohistochemistry, immunofluorescence, mass spectrometry, coimmunoprecipitation and multiplexed immunohistochemical staining were conducted to identify the specific regulatory mechanism in PDAC. The results verified that DDX3X expression is notably upregulated in the tumor tissue vs. normal tissue of PDAC patients. DDX3X knockdown markedly suppressed the proliferation, invasion and migration of PDAC cells in vitro and inhibited tumor growth in vivo. Conversely, overexpression of DDX3X induced the opposite effect. Further studies supported that the DDX3X protein can associate with sirtuin 7 (SIRT7) to stimulate PDAC carcinogenesis and progression. Furthermore, SIRT7 inhibition significantly impeded DDX3X-mediated tumor growth both ex vivo and in vivo. The results also revealed that programmed death ligand 1 (PD-L1) expression is positively correlated with DDX3X expression. These results reveal significant involvement of the DDX3X-SIRT7 axis in the initiation and advancement of PDAC and offer previously undiscovered therapeutic options for PDAC management.

Topical drug delivery strategies for enhancing drug effectiveness by skin barriers, drug delivery systems and individualized dosing

Topical drug delivery is widely used in various diseases because of the advantages of not passing through the gastrointestinal tract, avoiding gastrointestinal irritation and hepatic first-pass effect, and reaching the lesion directly to reduce unnecessary adverse reactions. The skin helps the organism to defend itself against a huge majority of external aggressions and is one of the most important lines of defense of the body. However, the skin's strong barrier ability is also a huge obstacle to the effectiveness of topical medications. Allowing the bioactive, composition in a drug to pass through the stratum corneum barrier as needed to reach the target site is the most essential need for the bioactive, composition to exert its therapeutic effect. The state of the skin barrier, the choice of delivery system for the bioactive, composition, and individualized disease detection and dosing planning influence the effectiveness of topical medications. Nowadays, enhancing transdermal absorption of topically applied drugs is the hottest research area. However, enhancing transdermal absorption of drugs is not the first choice to improve the effectiveness of all drugs. Excessive transdermal absorption enhances topical drug accumulation at non-target sites and the occurrence of adverse reactions. This paper introduces topical drug delivery strategies to improve drug effectiveness from three perspectives: skin barrier, drug delivery system and individualized drug delivery, describes the current status and shortcomings of topical drug research, and provides new directions and ideas for topical drug research.

BCKDHA contributes to melanoma progression by promoting the expressions of lipogenic enzymes FASN and ACLY

The dysregulation of branched-chain amino acid (BCAA) metabolism and related enzymes has been greatly implicated in the progression of multiple types of cancer, whereas remains far from understood in melanoma. Here, we explored the role of the BCAA metabolism enzyme BCKDHA in melanoma pathogenesis and elucidated the underlying mechanisms. In vitro cell biology experiments and in vivo pre-clinical mice model experiments were performed to investigate the role of BCKDHA in melanoma progression. RNA sequencing, immunohistochemical/immunofluorescence staining and bioinformatics analysis were used to examine the underlying mechanism. BCKDHA expression was prominently increased in both melanoma tissues and cell lines. The up-regulation of BCKDHA promoted long-term tumour cell proliferation, invasion and migration in vitro and tumour growth in vivo. Through RNA-sequencing technology, it was found that BCKDHA regulated the expressions of lipogenic fatty acid synthase (FASN) and ATP-citrate lyase (ACLY), which was thereafter proved to mediate the oncogenic role of BCKDHA in melanoma. Our results demonstrate that BCKDHA promotes melanoma progression by regulating FASN and ACLY expressions. Targeting BCKDHA could be exploited as a promising strategy to restrain tumour progression in melanoma.

The Role of XBP1 in bone metabolism

Bone is a dynamic organ that, once formed, undergoes a constant remodeling process that includes bone resorption and synthesis. Osteoclasts and osteoblasts are primarily responsible for controlling this process. X-box binding protein 1 (XBP1), a transcription factor, affects the metabolism of bones in various ways. In recent years, numerous studies have revealed that XBP1 plays a vital role in bone metabolism, including osteoclast and osteoblast development, as well as in regulating immune cell differentiation that affects the immune microenvironment of bone remodeling. In this review, we highlight the regulatory mechanisms of XBP1 on osteoclasts and osteoblasts, how XBP1 affects the immune microenvironment of bone remodeling by influencing the differentiation of immune cells, and predict the possible future research directions of XBP1 to provide new insights for the treatment of bone-related metabolic diseases.

Functional Diversity of SIRT7 Across Cellular Compartments: Insights and Perspectives

Posttranslational modifications (PTMs) play important roles in the regulation of protein function. Acetylation and deacetylation are among the most important PTMs. SIRT7 is a relatively understudied member of the sirtuin family, but recent studies have revealed that it plays a regulatory role in a variety of cellular activities, such as genome stabilization and repair, gene translation, ribosome production and other important processes. Here, we provide a list of the functions and mechanisms of SIRT7 in various organelles and show the important role of SIRT7 in maintaining normal cell function.