Aldose reductase participates in the downregulation of T cell functions due to suppressor macrophages

AKR1B1 Expression in the Colorectal Tumor Microenvironment Contributes Towards Its Prognostic Significance

BACKGROUND

AKR1B1, a member of the aldo-keto reductase enzyme family involved in the polyol pathway of aldehyde metabolism, is aberrantly expressed in colorectal cancer (CRC). Our previous studies demonstrated that AKR1B1 knockdown reduced the motility and proliferation of CRC cell lines, and its elevated expression was correlated with increased mesenchymal marker expression, inflammation, and poor prognosis in CRC patient cohorts. However, whether stromal cells also express AKR1B1 and whether stromal expression can affect clinical outcomes has not been examined.

OBJECTIVES

To evaluate the expression of AKR1B1 within the tumor microenvironment (TME) of CRC, with a paticular focus on stromal cells, and to assess its association with clinical outcomes.

METHODS

We assessed AKR1B1 expression in colorectal tumors utilizing publicly available transcriptomic data from CRC tumors. Single-cell RNA-sequencing data from CRC samples were analyzed to determine cell type-specific expression. Immunohistochemistry based assessment of AKR1B1 expression was performed in Turkish and Serbian cohorts. Co-localization of AKR1B1 and CD163 (M2 macrophage marker) was evaluated by immunoflourescence.

RESULTS

AKR1B1 was expressed in both the epithelial and stromal components of colorectal tumors, with higher expression observed in the stroma. Single-cell transcriptomic analysis revealed AKR1B1 expression in myeloid cells, T and NK cells, B cells, dendritic cells, fibroblasts, and epithelial cells. Notably, AKR1B1-expressing macrophages were predominantly of the M2 phenotype, and AKR1B1 expression and M2 marker expression showed strong positive correlation in bulk transcriptomic data. Immunofluorescence confirmed the colocalization of CD163 and AKR1B1 in stromal macrophages. Moreover, immunohistochemical analysis of AKR1B1 expression in tumor stroma from a cohort of Turkish patients revealed that its expression was associated with favorable overall survival, particularly in tumors with higher stromal infiltration.

CONCLUSIONS

Overall, our findings underscore the significant influence of the TME composition on the relationship between AKR1B1 expression and clinical outcomes.

Phosphoproteome of signaling by ErbB2 in ovarian cancer cells

The gene for receptor tyrosine kinase ErbB2 is amplified in breast and ovarian tumours. The linear pathway by which signals are transduced through ErbB2 are well known. However, second generation questions that address spatial aspects of signaling remain. To address this, we have undertaken a mass spectrometry approach to identify phosphoproteins specific for ErbB2 using the inhibitors Lapatinib and CP724714 in ovarian cancer cells. The ErbB2 specific proteins identified in SKOV-3 cells were Myristoylated alanine-rich C-kinase substrate, Protein capicua homolog, Protein peptidyl isomerase G, Protein PRRC2C, Chromobox homolog1 and PRP4 homolog. We have evaluated three phosphoproteins PKM2, Aldose reductase and MARCKS in SKOV-3 cells. We observed that PKM2 was phosphorylated by EGF but was not inhibited by Lapatinib and CP724714. The activity of aldose reductase in reducing NADPH as a substrate was significantly higher in EGF stimulated cells which was inhibited by Lapatinib and CP724714 but not by Geftinib (EGFR inhibitor). MARCKS was phosphorylated on stimulation of SKOV-3 cells with EGF that was inhibited by Lapatinib and CP724714 which was dependent on the kinase activity of ErbB2. These results have identified phosphoproteins that are specific to ErbB2 which have not been previously reported and sets the basis for future experiments.

Aldose Reductase: An Emerging Target for Development of Interventions for Diabetic Cardiovascular Complications

Diabetes is a leading cause of cardiovascular morbidity and mortality. Despite numerous treatments for cardiovascular disease (CVD), for patients with diabetes, these therapies provide less benefit for protection from CVD. These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify especially as the diabetes epidemic continues to expand. In this context, high levels of blood glucose stimulate the flux via aldose reductase (AR) pathway leading to metabolic and signaling changes in cells of the cardiovascular system. In animal models flux via AR in hearts is increased by diabetes and ischemia and its inhibition protects diabetic and non-diabetic hearts from ischemia-reperfusion injury. In mouse models of diabetic atherosclerosis, human AR expression accelerates progression and impairs regression of atherosclerotic plaques. Genetic studies have revealed that single nucleotide polymorphisms (SNPs) of the ALD2 (human AR gene) is associated with diabetic complications, including cardiorenal complications. This Review presents current knowledge regarding the roles for AR in the causes and consequences of diabetic cardiovascular disease and the status of AR inhibitors in clinical trials. Studies from both human subjects and animal models are presented to highlight the breadth of evidence linking AR to the cardiovascular consequences of diabetes.

Sensing of Bacterial Cyclic Dinucleotides by the Oxidoreductase RECON Promotes NF-κB Activation and Shapes a Proinflammatory Antibacterial State

Bacterial and host cyclic dinucleotides (cdNs) mediate cytosolic immune responses through the STING signaling pathway, although evidence suggests that alternative pathways exist. We used cdN-conjugated beads to biochemically isolate host receptors for bacterial cdNs, and we identified the oxidoreductase RECON. High-affinity cdN binding inhibited RECON enzyme activity by simultaneously blocking the substrate and cosubstrate sites, as revealed by structural analyses. During bacterial infection of macrophages, RECON antagonized STING activation by acting as a molecular sink for cdNs. Bacterial infection of hepatocytes, which do not express STING, revealed that RECON negatively regulates NF-κB activation. Loss of RECON activity, via genetic ablation or inhibition by cdNs, increased NF-κB activation and reduced bacterial survival, suggesting that cdN inhibition of RECON promotes a proinflammatory, antibacterial state that is distinct from the antiviral state associated with STING activation. Thus, RECON functions as a cytosolic sensor for bacterial cdNs, shaping inflammatory gene activation via its effects on STING and NF-κB.