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A innovative work conducted by Solier et al uncovered a druggable copper signaling pathway that propelled inflammation, through an integrated approach of cell biology, biochemistry, and chemistry methodologies. The authors began by generating inflammatory macrophages from human primary monocytes and observing their upregulation of CD44, a cell surface glycoprotein known to play roles in development, immunity, and cancer progression. To further explore the role of CD44, the authors used a mass spectrometry technique to measure copper levels in activated macrophages and found that CD44 knockdown reduced copper uptake. Additionally, the authors observed increased CD44 and copper uptake in inflammatory macrophages.

To further investigate the role of copper in inflammation, the authors designed a dimer of metformin, LCC-12, which can bind to and inactivate mitochondrial copper(II). LCC-12 was found to inhibit CD86 upregulation in activated macrophages and to reduce inflammation in animal models of acute inflammation.

a, GO term analysis of upregulated genes in aMDMs (n = 10 donors). Adj. P, adjusted P value. b, RNA-seq analysis of MDMs. Macrophage inflammatory signature genes are highlighted. The dashed line indicates an adjusted P value of 0.05 (n = 10 donors). c, RNA-seq analysis of MDMs. Iron-dependent demethylase and acetyltransferase signature genes are highlighted. The dashed line indicates an adjusted P value of 0.05 (n = 10 donors). d, Correlation for a representative donor of ChIP–seq reads count of histone marks in genes against RNA-seq of gene transcripts in MDMs (n = 10 donors). e, GO term analysis of genes in aMDMs (n = 10 donors) whose expression levels are downregulated upon treatment with LCC-12 (n = 5 donors). f, RNA-seq analysis of aMDMs (n = 10 donors) and MDMs treated with LCC-12 during activation (n = 5 donors). Macrophage inflammatory signature genes are highlighted. The dashed line indicates an adjusted P value of 0.05. g, Correlation for a representative donor of ChIP–seq reads count of histone marks in genes against RNA-seq of gene transcripts in aMDMs (n = 10 donors) and MDMs treated with LCC-12 during activation (n = 5 donors). h, RNA-seq analysis of CD44-knockout (KO) and wild-type (WT) aMDMs. Representative of n = 4 donors. Gating strategy is shown in the Supplementary Information. Macrophage inflammatory signature genes are highlighted. The dashed line indicates an adjusted P value of 0.05. In a–c,e,f, Differential gene expression was assessed with the limma/voom framework. GO enrichment was assessed with the enrichGO method from clusterProfiler. P values were corrected for multiple testing with the Benjamini–Hochberg procedure.

Credit:DOI:https://doi.org/10.1038/s41586-023-06017-4.

The authors then performed mass spectrometry to determine that LCC-12 targeted mitochondrial copper(II) in macrophages. To demonstrate this, the authors used fluorescent labeling and NanoSIMS imaging to confirm the subcellular localization of LCC-12 in mitochondria. Furthermore, they demonstrated that LCC-12 reduced the activity of mitochondrial enzymes dependent on NAD+ and attenuated NADH/NAD+ redox cycling.

Additionally, the authors conducted RNA sequencing and chromatin immunoprecipitation to demonstrate that LCC-12 induced metabolic and epigenetic shifts that opposed macrophage activation and dampened inflammation.

Finally, the authors used animal models to demonstrate that LCC-12 reduced inflammation in mouse models of bacterial, viral, and endotoxin-induced sepsis. The data presented in this study suggested that targeting mitochondrial copper(II) represented a novel therapeutic strategy for treating inflammatory diseases.

In conclusion, the authors have uncovered a novel copper signaling pathway that regulates inflammation. Their findings support the concept that mitochondrial copper(II) acts as a regulator of macrophage activation and inflammation, and that targeting mitochondrial copper(II) could represent a novel therapeutic strategy for treating inflammatory diseases. This study highlights the power of combining cell biology, biochemistry, and chemistry methods to uncover new signaling pathways that regulate important biological processes.

In addition to copper ions, zinc ions can also regulate cellular metabolism by modulating the levels of NAD⁺. Lei et al. developed a novel dual metabolism inhibitor, Zinc-Carnosine Metallodrug Network nanoparticles (Zn-Car MNs), to simultaneously inhibit OXPHOS and glycolysis in cancer cells. They achieved this by utilizing carnosine as the organic ligand and coordinating it with Zn ions to prepare Zn-Car MNs nanoparticles.

The authors found that Zn-Car MNs could effectively deplete intracellular copper, leading to the disintegration of the Zn-Car MNs structure and release of Zn ions and carnosine. The released Zn ions could cause oxidative stress and inhibit glycolysis, while the copper depletion could impair mitochondrial complex IV and reduce OXPHOS.

In vitro experiments demonstrated that Zn-Car MNs could significantly reduce COX activity, mitochondrial membrane potential, NAD⁺ content, lactate production, intracellular pH, and ATP levels in cancer cells. This resulted in apoptosis of cancer cells.

In vivo studies using breast cancer and colon cancer models showed that Zn-Car MNs could effectively inhibit tumor growth, outperforming the benchmark copper chelator tetrathiomolybdate (TM). The antitumor effect of Zn-Car MNs was attributed to the simultaneous inhibition of OXPHOS and glycolysis, which overcame the metabolic reprogramming of cancer cells.

In summary, the authors have developed Zn-Car MNs as a dual metabolism inhibitor to target both OXPHOS and glycolysis in cancer cells. This strategy can overcome drug resistance caused by metabolic reprogramming and holds potential clinical relevance for cancer therapy.

1. Solier S, Müller S, Cañeque T, Versini A, Mansart A, Sindikubwabo F, Baron L, Emam L, Gestraud P, Pantoș GD, Gandon V, Gaillet C, Wu TD, Dingli F, Loew D, Baulande S, Durand S, Sencio V, Robil C, Trottein F, Péricat D, Näser E, Cougoule C, Meunier E, Bègue AL, Salmon H, Manel N, Puisieux A, Watson S, Dawson MA, Servant N, Kroemer G, Annane D, Rodriguez R. A druggable copper-signalling pathway that drives inflammation. Nature. 2023 May;617(7960):386-394.

2. Lei L, Nan B, Yang F, Xu L, Guan G, Xu J, Yue R, Wang Y, Huan S, Yin X, Zhang XB, Song G. Zinc-Carnosine Metallodrug Network as Dual Metabolism Inhibitor Overcoming Metabolic Reprogramming for Efficient Cancer Therapy. Nano Lett. 2023 Apr 12;23(7):2659-2668.