A cell-type-specific role for murine Commd1 in liver inflammation

A Crosstalk Between Castration-Resistant Prostate Cancer Cells, M2 Macrophages, and NK Cells: Role of the ATM-PI3K/AKT-PD-L1 Pathway

Castration-resistant prostate cancer (CRPC) in males is associated with a poor prognosis and a higher risk of treatment-related adverse effects, with high mortality among cancers globally. It is thus imperative to explore novel potential molecules with dual therapeutic and biomarker functions. Based on the recent research findings, the expression levels of ataxia telangiectasia mutant kinase (ATM) in prostate cancer (PC) tissues collected from CRPC patients were higher than hormone-dependent PC patients. Using CRPC cell lines (C4-2 and CWR22Rv1), the transwell chamber experiments revealed ATM promoted macrophage recruitment in CRPC cells in vitro via C-X-C motif chemokine ligand 12 (CXCL12). Further in vitro investigations demonstrated that polarized macrophages prevented NK cell recruitment and reduced the immunocidal activity of NK cells against CRPC cell lines. Moreover, ATM boosted programmed death receptor ligand 1 (PD-L1) expression while inhibiting NK group 2D (NKG2D) ligand expression in selected cell lines via PI3K/AKT signaling pathway. The in vivo investigations revealed ATM induced proliferation of CRPC and macrophage recruitment, while the NK cell recruitment was found to suppress ATM expression and CRPC proliferation. In conclusion, it could be demonstrated that inhibiting ATM increased the susceptibility of CRPC to NK cell inhibitors by dampening the CXCL12 and PI3K/AKT-PD-L1 pathways, thereby offering a novel and individualized treatment protocol for treating CRPC.

COMMD proteins function and their regulating roles in tumors

The COMMD proteins are a highly conserved protein family with ten members that play a crucial role in a variety of biological activities, including copper metabolism, endosomal sorting, ion transport, and other processes. Recent research have demonstrated that the COMMD proteins are closely associated with a wide range of disorders, such as hepatitis, myocardial ischemia, cerebral ischemia, HIV infection, and cancer. Among these, the role of COMMD proteins in tumors has been thoroughly explored; they promote or inhibit cancers such as lung cancer, liver cancer, gastric cancer, and prostate cancer. COMMD proteins can influence tumor proliferation, invasion, metastasis, and tumor angiogenesis, which are strongly related to the prognosis of tumors and are possible therapeutic targets for treating tumors. In terms of molecular mechanism, COMMD proteins in tumor cells regulate the oncogenes of NF-κB, HIF, c-MYC, and others, and are related to signaling pathways including apoptosis, autophagy, and ferroptosis. For the clinical diagnosis and therapy of malignancies, additional research into the involvement of COMMD proteins in cancer is beneficial.

The hepatocyte IKK:NF-κB axis promotes liver steatosis by stimulating de novo lipogenesis and cholesterol synthesis

OBJECTIVE

Obesity-related chronic inflammation plays an important role in the development of Metabolic Associated Fatty Liver Disease (MAFLD). Although the contribution of the pro-inflammatory NF-κB signaling pathway to the progression from simple steatosis to non-alcoholic steatohepatitis (NASH) is well-established, its role as an initiator of hepatic steatosis and the underlying mechanism remains unclear. Here, we investigated the hypothesis that the hepatocytic NF-κB signaling pathway acts as a metabolic regulator, thereby promoting hepatic steatosis development.

METHODS

A murine model expressing a constitutively active form of IKKβ in hepatocytes (Hep-IKKβca) was used to activate hepatocyte NF-κB. In addition, IKKβca was also expressed in hepatocyte A20-deficient mice (IKKβca;A20^LKO). A20 is an NF-κB-target gene that inhibits the activation of the NF-κB signaling pathway upstream of IKKβ. These mouse models were fed a sucrose-rich diet for 8 weeks. Hepatic lipid levels were measured and using [1-¹³C]-acetate de novo lipogenesis and cholesterol synthesis rate were determined. Gene expression analyses and immunoblotting were used to study the lipogenesis and cholesterol synthesis pathways.

RESULTS

Hepatocytic NF-κB activation by expressing IKKβca in hepatocytes resulted in hepatic steatosis without inflammation. Ablation of hepatocyte A20 in Hep-IKKβca mice (IKKβca;A20^LKO mice) exacerbated hepatic steatosis, characterized by macrovesicular accumulation of triglycerides and cholesterol, and increased plasma cholesterol levels. Both De novo lipogenesis (DNL) and cholesterol synthesis were found elevated in IKKβca;A20^LKO mice. Phosphorylation of AMP-activated kinase (AMPK) - a suppressor in lipogenesis and cholesterol synthesis - was decreased in IKKβca;A20^LKO mice. This was paralleled by elevated protein levels of hydroxymethylglutaryl-CoA synthase 1 (HMGCS1) and reduced phosphorylation of HMG-CoA reductase (HMGCR) both key enzymes in the cholesterol synthesis pathway. Whereas inflammation was not observed in young IKKβca;A20^LKO mice sustained hepatic NF-κB activation resulted in liver inflammation, together with elevated hepatic and plasma cholesterol levels in middle-aged mice.

CONCLUSIONS

The hepatocytic IKK:NF-κB axis is a metabolic regulator by controlling DNL and cholesterol synthesis, independent of its central role in inflammation. The IKK:NF-κB axis controls the phosphorylation levels of AMPK and HMGCR and the protein levels of HMGCS1. Chronic IKK-mediated NF-κB activation may contribute to the initiation of hepatic steatosis and cardiovascular disease risk in MAFLD patients.

COMMD1, a multi-potent intracellular protein involved in copper homeostasis, protein trafficking, inflammation, and cancer

Copper is a trace element indispensable for life, but at the same time it is implicated in reactive oxygen species formation. Several inherited copper storage diseases are described of which Wilson disease (copper overload, mutations in ATP7B gene) and Menkes disease (copper deficiency, mutations in ATP7A gene) are the most prominent ones. After the discovery in 2002 of a novel gene product (i.e. COMMD1) involved in hepatic copper handling in Bedlington terriers, studies on the mechanism of action of COMMD1 revealed numerous non-copper related functions. Effects on hepatic copper handling are likely mediated via interactions with ATP7B. In addition, COMMD1 has many more interacting partners which guide their routing to either the plasma membrane or, often in an ubiquitination-dependent fashion, trigger their proteolysis via the S26 proteasome. By stimulating NF-κB ubiquitination, COMMD1 dampens an inflammatory reaction. Finally, targeting COMMD1 function can be a novel approach in the treatment of tumors.

Function of the endolysosomal network in cholesterol homeostasis and metabolic-associated fatty liver disease (MAFLD)

Background

Metabolic-associated fatty liver disease (MAFLD), also known as non-alcoholic fatty liver disease, has become the leading cause of chronic liver disease worldwide. In addition to hepatic accumulation of triglycerides, dysregulated cholesterol metabolism is an important contributor to the pathogenesis of MAFLD. Maintenance of cholesterol homeostasis is highly dependent on cellular cholesterol uptake and, subsequently, cholesterol transport to other membrane compartments, such as the endoplasmic reticulum (ER).

Scope of review

The endolysosomal network is key for regulating cellular homeostasis and adaptation, and emerging evidence has shown that the endolysosomal network is crucial to maintain metabolic homeostasis. In this review, we will summarize our current understanding of the role of the endolysosomal network in cholesterol homeostasis and its implications in MAFLD pathogenesis.

Major conclusions

Although multiple endolysosomal proteins have been identified in the regulation of cholesterol uptake, intracellular transport, and degradation, their physiological role is incompletely understood. Further research should elucidate their role in controlling metabolic homeostasis and development of fatty liver disease.

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The intracellular cholesterol transport is tightly regulated by the endocytic and lysosomal network.

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Dysfunction of the endolysosomal network affects hepatic lipid homeostasis.

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The endosomal sorting of lipoprotein receptors is precisely regulated and is not a bulk process.

Impaired Hepatic Vitamin A Metabolism in NAFLD Mice Leading to Vitamin A Accumulation in Hepatocytes

BACKGROUND & AIMS

Systemic retinol (vitamin A) homeostasis is controlled by the liver, involving close collaboration between hepatocytes and hepatic stellate cells (HSCs). Genetic variants in retinol metabolism (PNPLA3 and HSD17B13) are associated with non-alcoholic fatty liver disease (NAFLD) and disease progression. Still, little mechanistic details are known about hepatic vitamin A metabolism in NAFLD, which may affect carbohydrate and lipid metabolism, inflammation, oxidative stress and the development of fibrosis and cancer, e.g. all risk factors of NAFLD.

METHODS

Here, we analyzed vitamin A metabolism in 2 mouse models of NAFLD; mice fed a high-fat, high-cholesterol (HFC) diet and Leptinob mutant (ob/ob) mice.

RESULTS

Hepatic retinol and retinol binding protein 4 (RBP4) levels were significantly reduced in both mouse models of NAFLD. In contrast, hepatic retinyl palmitate levels (the vitamin A storage form) were significantly elevated in these mice. Transcriptome analysis revealed a hyperdynamic state of hepatic vitamin A metabolism, with enhanced retinol storage and metabolism (upregulated Lrat, Dgat1, Pnpla3, Raldh's and RAR/RXR-target genes) in fatty livers, in conjunction with induced hepatic inflammation (upregulated Cd68, Tnfα, Nos2, Il1β, Il-6) and fibrosis (upregulated Col1a1, Acta2, Tgfβ, Timp1). Autofluorescence analyses revealed prominent vitamin A accumulation in hepatocytes rather than HSC in HFC-fed mice. Palmitic acid exposure increased Lrat mRNA levels in primary rat hepatocytes and promoted retinyl palmitate accumulation when co-treated with retinol, which was not detected for similarly-treated primary rat HSCs.

CONCLUSION

NAFLD leads to cell type-specific rearrangements in retinol metabolism leading to vitamin A accumulation in hepatocytes. This may promote disease progression and/or affect therapeutic approaches targeting nuclear receptors.

Nuclear COMMD1 Is Associated with Cisplatin Sensitivity in Ovarian Cancer

Copper metabolism MURR1 domain 1 (COMMD1) protein is a multifunctional protein, and its expression has been correlated with patients’ survival in different types of cancer. In vitro studies revealed that COMMD1 plays a role in sensitizing cancer cell lines to cisplatin, however, the mechanism and its role in platinum sensitivity in cancer has yet to be established. We evaluated the role of COMMD1 in cisplatin sensitivity in A2780 ovarian cancer cells and the relation between COMMD1 expression and response to platinum-based therapy in advanced stage high-grade serous ovarian cancer (HGSOC) patients. We found that elevation of nuclear COMMD1 expression sensitized A2780 ovarian cancer cells to cisplatin-mediated cytotoxicity. This was accompanied by a more effective G₂/M checkpoint, and decreased protein expression of the DNA repair gene BRCA1, and the apoptosis inhibitor BCL2. Furthermore, COMMD1 expression was immunohistochemically analyzed in two tissue micro-arrays (TMAs), representing a historical cohort and a randomized clinical trial-based cohort of advanced stage HGSOC tumor specimens. Expression of COMMD1 was observed in all ovarian cancer samples, however, specifically nuclear expression of COMMD1 was only observed in a subset of ovarian cancers. In our historical cohort, nuclear COMMD1 expression was associated with an improved response to chemotherapy (OR = 0.167; P = 0.038), although this association could not be confirmed in the second cohort, likely due to sample size. Taken together, these results suggest that nuclear expression of COMMD1 sensitize ovarian cancer to cisplatin, possibly by modulating the G₂/M checkpoint and through controlling expression of genes involved in DNA repair and apoptosis.

CCC- and WASH-mediated endosomal sorting of LDLR is required for normal clearance of circulating LDL

The low-density lipoprotein receptor (LDLR) plays a pivotal role in clearing atherogenic circulating low-density lipoprotein (LDL) cholesterol. Here we show that the COMMD/CCDC22/CCDC93 (CCC) and the Wiskott–Aldrich syndrome protein and SCAR homologue (WASH) complexes are both crucial for endosomal sorting of LDLR and for its function. We find that patients with X-linked intellectual disability caused by mutations in CCDC22 are hypercholesterolaemic, and that COMMD1-deficient dogs and liver-specific Commd1 knockout mice have elevated plasma LDL cholesterol levels. Furthermore, Commd1 depletion results in mislocalization of LDLR, accompanied by decreased LDL uptake. Increased total plasma cholesterol levels are also seen in hepatic COMMD9-deficient mice. Inactivation of the CCC-associated WASH complex causes LDLR mislocalization, increased lysosomal degradation of LDLR and impaired LDL uptake. Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is associated with hypercholesterolaemia in humans. Altogether, this study provides valuable insights into the mechanisms regulating cholesterol homeostasis and LDLR trafficking.

Low density lipoprotein receptor (LDLR) is crucial for cholesterol homeostasis. Here, the authors show that components of the CCC-protein complex, CCDC22 and COMMD1, facilitate the endosomal sorting of LDLR and that mutations in these genes cause hypercholesterolemia in dogs and mice, providing new insights into regulation of cholesterol homeostasis.

Copper metabolism domain-containing 1 represses the mediators involved in the terminal effector pathways of human labour and delivery

STUDY HYPOTHESIS

Does Copper Metabolism MURR1 Domain 1 (COMMD1) play a role in regulating the mediators involved in the terminal processes of human labour and delivery?

STUDY FINDING

COMMD1 plays a critical role in the termination of nuclear factor-κB (NF-κB) activity and the control of pro-inflammatory and pro-labour mediators.

WHAT IS KNOWN ALREADY

Inflammation and infection are the biggest aetiological factors associated with preterm birth. NF-κB drives the transcription of pro-inflammatory mediators involved in the terminal effector pathways of human labour and delivery. In non-gestational tissues, COMMD1 is a negative regulator of NF-κB-induced inflammation.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

The mRNA and/or protein level of COMMD1 was assessed in myometrium (n = 8 per group) and fetal membranes (n = 8 per group) obtained from term non-labouring and labouring women at term, and fetal membranes (n = 8 per group) at preterm with and without histological chorioamnionitis. Primary human myometrial cells were used to determine the effect of pro-inflammatory mediators on COMMD1 level, and the effect of COMMD1 small interfering RNA (siRNA) on pro-labour mediators. Statistical significance was ascribed to a P < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

COMMD1 expression was significantly decreased with spontaneous term labour in myometrium; in fetal membranes with histologically confirmed chorioamnionitis and in myometrial cells treated with pro-inflammatory cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, the bacterial product fibroblast-stimulating lipopeptide and the viral double stranded RNA analogue polyinosinic polycytidilic acid. Loss-of-function studies revealed an increase in inflammation- and infection-induced TNF-α, IL-1α, IL-1β, IL-6, IL-8 and/or monocyte chemoattractant protein-1 mRNA abundance and/or release; and cyclo-oxygenase-2 mRNA level, release of prostaglandin (PG) F2α and mRNA level of the PGF2α receptor FP. In addition, siRNA knockdown of COMMD1 was associated with significantly increased NF-κB activation as evidenced by increased IL-1β-induced IκB-α protein degradation and NF-κB DNA binding activity.

LIMITATIONS, REASONS FOR CAUTION

The conclusions are based on in vitro experiments with cells isolated from myometrium. Animal models, however, will be required to establish whether COMMD1 activators can prevent spontaneous preterm birth in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

The control of COMMD1 activation may provide an alternative therapeutic strategy for reducing the release of pro-labour mediators in spontaneous preterm labour.

LARGE SCALE DATA

Not applicable.

STUDY FUNDING AND COMPETING INTERESTS

Associate Professor Martha Lappas is supported by a Career Development Fellowship from the National Health and Medical Research Council (NHMRC; grant no. 1047025). Additional funding was provided by the Medical Research Foundation for Women and Babies and the Mercy Research Foundation. The author has no conflict of interest.

COMMD1 regulates inflammation and colitis-associated cancer progression

NF-κB is a master transcriptional regulator of inflammation that plays an important role in oncogenesis, particularly in tumors that arise in the context of inflammation. Copper metabolism MURR1 domain-containing 1 (COMMD1) is a negative regulator of NF-κB. Recent genetic-based studies in both mice and human patients indicate that COMMD1 has an important role in controlling intestinal inflammation and constraining progression to colitis-associated cancer.