Regulation mechanism of PDK1 on macrophage metabolism and function

Identification of key mitochondria-related genes and their potential crosstalk role with immune pattern in Idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) stands out as a life-threatening and one of the most severe interstitial lung diseases. The pathogenesis of IPF is not fully understood, while recent studies have highlighted the association of mitochondrial dysfunction with IPF. This study is dedicated to pinpointing crucial genes related to mitochondria that potentially impact the advancement of IPF, thereby offering new perspectives on the pathogenesis of this condition.

METHODS

The Gene Expression Omnibus (GEO) database was utilized to download three datasets (GSE32537, GSE92592, and GSE150910), following which a comprehensive analysis was conducted to identify differentially expressed mitochondria-related genes (DEMTRGs) in the IPF lung tissues. Subsequently, GO and KEGG enrichment analysis of the DEMTRGs was performed. Next, external datasets and in vivo experiments were performed to validate their expression. Additionally, a Logistic regression model based on key DEMTRGs was constructed, and the model's ability to distinguish between IPF and controls was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). Finally, gene set enrichment analysis (GSEA) and CIBERSORT algorithm were conducted.

RESULTS

We identified five key DEMTRGs (ALDH18A1, ALDH1B1, MCCC1, ACAT1, and PDHA1), ALDH18A1 and ALDH1B1 exhibited upregulated expression levels, whereas MCCC1, ACAT1, and PDHA1 showed downregulation in the lung tissue of individuals with IPF. The expression levels of these key DEMTRGs were validated by an independent external dataset (GSE53845) and the bleomycin-induced pulmonary fibrosis mice. In addition, the ROCs indicated that the diagnostic model constructed based on key DEMTRGs could effectively distinguish between IPF and controls (AUC>0.8). GSEA analysis and immune-related analysis shed light on the potential mechanisms through which these key DEMTRGs influence IPF.

CONCLUSION

Our research has pinpointed key genes associated with mitochondria that may ultimately contribute to the progression of IPF by exerting regulatory effects on mitochondrial function, thereby influencing multiple cellular processes.

Identification and evolution of PDK-1-like involving lamprey innate immunity

3-phosphoinositide-dependent protein kinase-1 (PDK-1) is a key kinase regulating the activity of the PI3K/AKT pathway and a major regulator of the AGC protein kinase family. It is essential in the physiological activities of cells, embryonic development, individual development and immune response. In this study, we have identified for the first time an analogue of PDK-1 in the most primitive vertebrate, lamprey, and named it PDK-1-like. The protein sequence similarity of lamprey PDK-1-like to human, mouse, chicken, African xenopus and zebrafish PDK-1 were 64.4 %, 64.5 %, 65.0 %, 61.3 % and 63.2 %, respectively. The phylogenetic tree showed that PDK-1-like of lamprey were located at the base of the vertebrate branch, in line with the trend of biological evolution. Meanwhile, homology analysis showed that PDK-1 proteins across species shared a conserved kinase structural domain and a Pleckstrin Homology (PH) domain. Genomic synteny analysis revealed that the large-scale duplication blocks were not found in lamprey genome and neighbor genes of lamprey PDK-1-like presented dramatic differences compared with jawed vertebrates. More importantly, qPCR analysis showed that PDK-1-like was widely expressed in lamprey. Its mRNA expression levels varied in response to different pathogenic stimuli, and its expression was generally up-regulated under Polyinosinic-Polycytidylic acid (Poly(I:C)) stimulation. Pearson's correlation analysis showed that PDK-1-like was involved in co-expressed with MyD88-independent TLR-3 pathway during the immune response of lamprey, instead of MyD88-dependent TLR-3 pathway. In summary, our composite results offer valuable clues to the origin and evolution of PDK-1, and imply that PDK-1 s are among the most ancestral immune regulators in vertebrates.

Quercetin Limits Tumor Immune Escape through PDK1/CD47 Axis in Melanoma

Quercetin (3,3[Formula: see text],4[Formula: see text],5,7-pentahydroxyflavone) is a bioactive plant-derived flavonoid, abundant in fruits and vegetables, that can effectively inhibit the growth of many types of tumors without toxicity. Nevertheless, the effect of quercetin on melanoma immunology has yet to be determined. This study aimed to investigate the role and mechanism of the antitumor immunity action of quercetin in melanoma through both in vivo and in vitro methods. Our research revealed that quercetin has the ability to boost antitumor immunity by modulating the tumor immune microenvironment through increasing the percentages of M1 macrophages, CD8[Formula: see text] T lymphocytes, and CD4[Formula: see text] T lymphocytes and promoting the secretion of IL-2 and IFN-[Formula: see text] from CD8[Formula: see text] T cells, consequently suppressing the growth of melanoma. Furthermore, we revealed that quercetin can inhibit cell proliferation and migration of B16 cells in a dose-dependent manner. In addition, down-regulating PDK1 can inhibit the mRNA and protein expression levels of CD47. In the rescue experiment, we overexpressed PDK1 and found that the protein and mRNA expression levels of CD47 increased correspondingly, while the addition of quercetin reversed this effect. Moreover, quercetin could stimulate the proliferation and enhance the function of CD8[Formula: see text] T cells. Therefore, our results identified a novel mechanism through which CD47 is regulated by quercetin to promote phagocytosis, and elucidated the regulation of quercetin on macrophages and CD8[Formula: see text] T cells in the tumor immune microenvironment. The use of quercetin as a therapeutic drug holds potential benefits for immunotherapy, enhancing the efficacy of existing treatments for melanoma.

Loss of PDK1 Induces Meiotic Defects in Oocytes From Diabetic Mice

Maternal diabetes has been shown to impair oocyte quality; however, the underlying mechanisms remain unclear. Here, using a streptozotocin (STZ)-induced diabetic mouse model, we first detected and reduced expression of pyruvate dehydrogenase kinase 1 (PDK1) in diabetic oocytes, accompanying with the lowered phosphorylation of serine residue 232 on α subunit of the pyruvate dehydrogenase (PDH) complex (Ser232-PDHE1α). Importantly, forced expression of PDK1 not only elevated the phosphorylation level of Ser232-PDHE1α, but also partly prevented the spindle disorganization and chromosome misalignment in oocytes from diabetic mice, with no beneficial effects on metabolic dysfunction. Moreover, a phospho-mimetic S232D-PDHE1α mutant is also capable of ameliorating the maternal diabetes-associated meiotic defects. In sum, our data indicate that PDK1-controlled Ser232-PDHE1α phosphorylation pathway mediates the effects of diabetic environment on oocyte competence.

Haploinsufficiency of ATP6V0C possibly underlies 16p13.3 deletions that cause microcephaly, seizures, and neurodevelopmental disorder

We recently contributed to the description of eight individuals with a novel condition caused by 16p13.3 microdeletions encompassing TBC1D24, ATP6V0C, and PDPK1 and resulting in epilepsy, microcephaly and neurodevelopmental problems. The phenotypic spectrum, the minimum overlapping region and the underlying disease mechanism for this disorder remain to be clarified. Here we report a 3.5-year-old male, with microcephaly, autism spectrum disorder and a de novo 16p13.3 microdeletion. We performed detailed in silico analysis to show that the minimum overlapping region for the condition is ~80Kb encompassing five protein coding genes. Analysis of loss of function constraint metrics, transcript-aware evaluation of the population variants, GeVIR scores, analysis of reported pathogenic point variants, detailed review of the known functions of gene products and their animal models showed that the haploinsufficiency of ATP6V0C likely underlies the phenotype of this condition. Protein-protein interaction network, gene phenology and analysis of topologically associating domain showed that it was unlikely that the disorder has an epistatic or regulatory basis. 16p13.3 deletions encompassing ATP6V0C cause a neurodevelopmental disorder. Our results broaden the phenotypic spectrum of this disorder and clarify the likely underlying disease mechanism for the condition.

microRNA-145-3p inhibits non-small cell lung cancer cell migration and invasion by targeting PDK1 via the mTOR signaling pathway

The mammalian target of rapamycin (mTOR) pathway is dysregulated in more than 50% of all human malignancies and is a major target in cancer treatment. In this study, we explored the underlying mechanism involving microRNA-145-3p (miR-145-3p) in the development and progression of non-small cell lung cancer (NSCLC) by targeting PDK1 via the mTOR signaling pathway. NSCLC tissues and adjacent normal tissues were obtained from 83 NSCLC patients. miR-145-3p, PDK1, and mTOR levels were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry. Human NSCLC cell lines A549 and H1299 were transfected with miR-145-3p and siPDK1 to confirm the effect of miR-145-3p and PDK1 on NSCLC cells in vitro. Cell growth was evaluated by a CCK8 assay. Cell motility and chemotaxis analysis were determined by the scratch test and chemotaxis assay, respectively. The protein levels of PDK1 and mTOR were measured using the western blotting. Results showed lower level of miR-145-3p and higher levels of PDK1 and mTOR in NSCLC tissues compared to the adjacent normal tissues. In vitro results showed that cell growth, cell motility, and chemotaxis were all inhibited in cells transfected with miR-145-3p and those transfected with siPDK. Additionally, dual luciferase reporter gene assay helped confirmed that PDK1 is a target of miR-145. Finally, levels of PDK1, mTOR, and phosphorylated-mTOR were lower in cells transfected with miR-145-3p as well as those with siPDK1. These findings indicate that miR-145-3p may inhibit cell growth, motility, and chemotaxis in NSCLC by targeting PDK1 through suppressing the mTOR pathway.

Hemoadsorption corrects hyperresistinemia and restores anti-bacterial neutrophil function

Background

Mounting evidence suggests that sepsis-induced morbidity and mortality are due to both immune activation and immunosuppression. Resistin is an inflammatory cytokine and uremic toxin. Septic hyperresistinemia (plasma resistin >20 ng/ml) has been associated with greater disease severity and worse outcomes, and it is further exacerbated by concomitant acute kidney injury (AKI). Septic hyperresistinemia disturbs actin polymerization in neutrophils leading to impaired neutrophil migration, a crucial first-line mechanism in host defense to bacterial infection. Our experimental objective was to study the effects of hyperresistinemia on other F-actin-dependent neutrophil defense mechanisms, in particular intracellular bacterial clearance and generation of reactive oxygen species (ROS). We also sought to examine the effects of hemoadsorption on hyperresistinemia and neutrophil dysfunction.

Methods

Thirteen patients with septic shock and six control patients were analyzed for serum resistin levels and their effects on neutrophil migration. In vitro, following incubation with resistin-spiked serum samples, Pseudomonasaeruginosa clearance and ROS generation in neutrophils were measured. Phosphorylation of 3-phosphoinositide-dependent protein kinase-1 (PDPK1) was assessed using flow cytometry. In vitro hemoadsorption with both Amberchrome™ columns (AC) and CytoSorb® cartridges (CC) were used to test correction of hyperresistinemia. We further tested AC for their effect on cell migration and ROS generation and CC for their effect on bacterial clearance.

Results

Patients with septic shock had higher serum resistin levels than control ICU patients and showed a strong, negative correlation between hyperresistinemia and neutrophil transwell migration (ρ= − 0.915, p < 0.001). In vitro, neutrophils exposed to hyperresistinemia exhibited twofold lower intracellular bacterial clearance rates compared to controls. Resistin impaired intracellular signaling and ROS production in a dose-dependent manner. Hemoadsorption with AC reduced serum concentrations of resistin and restored neutrophil migration and generation of ROS to normal levels. Hemoadsorption with CC also corrected hyperresistinemia and reconstituted normal intracellular bacterial clearance.

Conclusions

Septic hyperresistinemia strongly correlates with inhibition of neutrophil migration in vitro. Hyperresistinemia itself reversibly impairs neutrophil intracellular bacterial clearance and ROS generation. Hemoadsorption therapy with a clinically approved device corrects hyperresistinemia and neutrophil dysfunction. It may therefore provide a therapeutic option to improve neutrophil function during septic hyperresistinemia and ultimately alleviate immunosuppression in this disease state.