Rap1b-loss increases neutrophil lactate dehydrogenase activity to enhance neutrophil migration and acute inflammation in vivo

Hepatocyte-specific RAP1B deficiency ameliorates high-fat diet-induced obesity and liver inflammation in mice

AIM

This study investigated the role of RAP1B in hepatic lipid metabolism and its implications in obesity and associated metabolic disorders, focusing on the molecular mechanisms through which RAP1B influences lipid accumulation, inflammation and oxidative stress in liver tissues and hepatocyte cell lines.

MATERIALS AND METHODS

Liver-specific RAP1B-knockout (LKO) and overexpression (OE) mice were generated and fed a high-fat diet for 18 weeks to evaluate systemic and hepatic metabolic changes. Comprehensive metabolic phenotyping included measurements of body weight, body fat content, activity levels, energy expenditure (EE), respiratory exchange ratio (RER), glucose tolerance test and insulin tolerance test. RAP1B-knockdown AML12 hepatocytes were used for in vitro studies. Comprehensive transcriptome and metabolome analyses identified differentially expressed genes and key metabolic shifts. Biochemical and histological analyses were performed to assess lipid accumulation, oxidative stress and inflammatory markers.

RESULTS

We found that LKO mice exhibited significant reductions in body weight, fat pad size and liver mass, along with decreased hepatic lipid accumulation due to enhanced lipid breakdown. These mice demonstrated improved glucose tolerance and insulin sensitivity without changes in food intake. Liver histology showed reduced F4/80-positive macrophage infiltration, indicating decreased inflammatory cell recruitment. Additionally, markers of oxidative stress were significantly lower, and molecular analysis revealed downregulation of the MAPK(p38) and NF-κB signaling pathways, further supporting an anti-inflammatory hepatic environment. In contrast, OE mice showed increased liver weight, aggravated hepatic lipid accumulation driven by enhanced lipogenesis, worsened insulin resistance and elevated inflammation.

CONCLUSIONS

This study highlights RAP1B's pivotal role in hepatic metabolism and positions it as a potential therapeutic target for obesity and related metabolic disorders.

Lactylation-related molecular subtyping reveals the immune heterogeneity and clinical characteristics in ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease linked to early-onset colorectal cancer and metabolic abnormalities. While intestinal lactate disturbances are observed in UC, the role of lactate and lactylation in its pathogenesis remains unclear. The lack of specific biomarkers reflecting these processes limits understanding of their biological significance.

METHODS

UC subtypes were classified using ConsensusClusterPlus and NMF based on LRGs. Immune infiltration was assessed with ssGSEA, xCell, and CIBERSORT. WGCNA identified subtype-specific gene modules, and Lasso regression pinpointed hub genes. Single-cell analysis determined cellular localization, while WB and IHC validated findings in clinical, mouse, and cell models. Prognostic machine learning models evaluated the clinical significance of these results.

RESULTS

LRGs distinguished UC patients from controls and stratified them into high and low immune infiltration groups. MSN and MAPRE1, strongly linked to UC, showed elevated expression in vitro and in vivo. They aid in diagnosing UC and UC-associated colorectal cancer and serve as predictors of UC severity and response to immunosuppressants.

CONCLUSION

Using high-throughput transcriptomic data, we identified hub LRGs and highlighted the role of lactate-mediated lactylation in UC. MSN and MAPRE1 were confirmed to be upregulated in an inflammatory environment, underscoring their potential for personalized UC diagnosis and treatment.

Lactate: A key regulator of the immune response

Lactate, the end product of both anaerobic and aerobic glycolysis in proliferating and growing cells-with the latter process known as the Warburg effect-is historically considered a mere waste product of cell and tissue metabolism. However, research over the past ten years has unveiled multifaceted functions of lactate that critically shape and impact cellular biology. Beyond serving as a fuel source, lactate is now known to influence gene expression through histone modification and to function as a signaling molecule that impacts a wide range of cellular activities. These properties have been particularly studied in the context of both adaptive and innate immune responses. Here, we review the diverse roles of lactate in the regulation of the immune system during homeostasis and disease pathogenesis (including cancer, infection, cardiovascular diseases, and autoimmunity). Furthermore, we describe recently proposed therapeutic interventions for manipulating lactate metabolism in human diseases.

Lactate's impact on immune cells in sepsis: unraveling the complex interplay

Lactate significantly impacts immune cell function in sepsis and septic shock, transcending its traditional view as just a metabolic byproduct. This review summarizes the role of lactate as a biomarker and its influence on immune cell dynamics, emphasizing its critical role in modulating immune responses during sepsis. Mechanistically, key lactate transporters like MCT1, MCT4, and the receptor GPR81 are crucial in mediating these effects. HIF-1α also plays a significant role in lactate-driven immune modulation. Additionally, lactate affects immune cell function through post-translational modifications such as lactylation, acetylation, and phosphorylation, which alter enzyme activities and protein functions. These interactions between lactate and immune cells are central to understanding sepsis-associated immune dysregulation, offering insights that can guide future research and improve therapeutic strategies to enhance patient outcomes.

Risk score constructed with neutrophil extracellular traps-related genes predicts prognosis and immune microenvironment in multiple myeloma

Background

Multiple myeloma (MM) exhibits considerable heterogeneity in treatment responses and survival rates, even when standardized care is administered. Ongoing efforts are focused on developing prognostic models to predict these outcomes more accurately. Recently, neutrophil extracellular traps (NETs) have emerged as a potential factor in MM progression, sparking investigation into their role in prognostication.

Methods

In this study, a multi-gene risk scoring model was constructed using the intersection of NTEs and differentially expressed genes (DEGs), applying the least absolute shrinkage and selection operator (LASSO) Cox regression model. A nomogram was established, and the prognostic model's effectiveness was determined via Kaplan-Meier survival analysis, receiver operating characteristic (ROC) curve, and decision curve analysis (DCA). The ESTIMATE algorithm and immune-related single-sample gene set enrichment analysis (ssGSEA) were employed to evaluate the level of immune infiltration. The sensitivity of chemotherapy drugs was assessed using the Genomics of Drug Sensitivity in Cancer (GDSC) database. Ultimately, the presence of the detected genes was confirmed through quantitative real-time polymerase chain reaction (qRT-PCR) analysis in MM cell specimens.

Results

64 NETs-DEGs were yielded, and through univariate Cox regression and LASSO regression analysis, we constructed a risk score composed of six genes: CTSG, HSPE1, LDHA, MPO, PINK1, and VCAM1. MM patients in three independent datasets were classified into high- and low-risk groups according to the risk score. The overall survival (OS) of patients in the high-risk group was significantly reduced compared to the low-risk group. Furthermore, the risk score was an independent predictive factor for OS. In addition, interactions between the risk score, immune score, and immune cell infiltration were investigated. Further analysis indicated that patients in the high-risk group were more sensitive to a variety of chemotherapy and targeted drugs, including bortezomib. Moreover, the six genes provided insights into the progression of plasma cell disorders.

Conclusion

This study offers novel insights into the roles of NETs in prognostic prediction, immune status, and drug sensitivity in MM, serving as a valuable supplement and enhancement to existing grading systems.

MicroR-380-3p Reduces Sepsis-Induced Acute Kidney Injury via Regulating RAB1P to Restrain NF-κB Pathway

Septic acute kidney injury (AKI) is a common complication in critically ill patients with high morbidity and mortality. This study intends to clarify the clinical value and molecular mechanism of microR-380-3p in septic AKI by recruiting patients with septic AKI and establishing septic AKI cell models. Patients with septic AKI were included and human kidney-2 (HK-2) cells were induced by lipopolysaccharide (LPS) to construct the AKI cell model of sepsis. The expression of microR-380-3p was detected by quantitative real-time RT-PCR (qRT-PCR). The expression of Bax, cleaved caspase 3, Bcl-2, p65, and p-p65 was detected by Western blot. The contents of inflammation and oxidation were determined by commercial kits. Bioinformatics predicted the binding target of microR-380-3p and a dual luciferase reporting system was used to verify the regulatory relationship between microR-380-3p and RAP1B. The concentration of microR-380-3p was elevated in patients with septic AKI and appeared to be a biomarker for these patients. Silenced microR-380-3p reversed the damage of LPS on HK-2 cells via promoting viability, inhibiting apoptosis, inflammation, and oxidation. RAP1B was a target of microR-380-3p and microR-380-3p exerted targeted inhibition of RAP1B expression level. Down-regulation of RAP1B reversed the influence of silenced microR-380-3p on HK-2 cells. MicroR-380-3p/RAP1B participated in activating the NF-κB pathway. MicroR-380-3p down-regulated RAP1B to exacerbate septic AKI, providing a potential therapeutic biomarker for septic AKI.

Single-cell sequencing of the retina shows that LDHA regulates pathogenesis of autoimmune uveitis

Autoimmune uveitis (AU) is a severe disorder causing poor vision and blindness. However, the cellular dynamics and pathogenic mechanisms underlying retinal injury in uveitis remain unclear. In this study, single-cell RNA sequencing of the retina and cervical draining lymph nodes in experimental autoimmune uveitis mice was conducted to identify the cellular spatiotemporal dynamics and upregulation of the glycolysis-related gene LDHA. Suppression of LDHA can rescue the imbalance of T effector (Teff) cells/T regulator (Treg) cells under inflammation via downregulation of the glycolysis-PI3K signaling circuit and inhibition of the migration of CXCR4+ Teff cells towards retinal tissue. Furthermore, LDHA and CXCR4 are upregulated in the peripheral blood mononuclear cells of Vogt-Koyanagi-Harada patients. The LDHA inhibitor suppresses CD4+ T cell proliferation in humans. Therefore, our data indicate that the autoimmune environment of uveitis regulates Teff cell accumulation in the retina via glycolysis-associated LDHA. Modulation of this target may provide a novel therapeutic strategy for treating AU.

High serum lactate dehydrogenase to albumin ratio is associated with increased risk of poor prognosis after ischemic stroke

BACKGROUND

Lactate dehydrogenase to albumin ratio (LAR) is a comprehensive biomarker for anaerobiosis, inflammation, and nutritional status, but its prognostic value for ischemic stroke has rarely been reported. We aimed to prospectively investigate whether serum LAR is associated with the prognosis of ischemic stroke patients in a large-scale cohort study.

MATERIALS AND METHODS

Serum LAR levels were measured among 6634 patients with ischemic stroke admitted at Minhang hospital from January 2018 to December 2022. The primary outcome was the composite of major disability and death (modified Rankin Scale score [mRS] ≥ 3) at 3-month follow up. Secondary outcomes included death and the ordered 7-level category score of mRS. Multivariate logistic regression and restricted cubic splines were adopted to evaluate the associations between serum LAR levels and adverse clinical outcomes of ischemic stroke.

RESULTS

During 3 months of follow-up period, a total of 2125 patients experienced primary outcome. After multivariate adjustment, the highest quartile of serum LAR was associated with an increased risk of primary outcome (odds ratio [OR], 1.52; 95% confidence interval [CI], 1.27-1.83; P for trend < 0.001). Each standard deviation higher log-transformed serum LAR resulted in a 20% (95% CI, 12%-28%) increased risk of primary outcome. Furthermore, multivariable-adjusted restricted cubic spline analyses showed a linear association between the serum LAR level with primary outcome (P for linearity < 0.001). Finally, the addition of serum LAR to conventional risk factors significantly improved risk predictive abilities for the primary outcome (net reclassification improvement [NRI]: 18.35%, P < 0.001; integrated discrimination improvement [IDI]: 0.35%, P < 0.001) at 3-month follow up in patients with ischemic stroke.

CONCLUSION

High serum LAR level was independently associated with an increased risk of adverse clinical outcomes among patients with ischemic stroke, indicating that serum LAR may be a valuable prognostic biomarker for ischemic stroke.

High serum lactate dehydrogenase as a predictor of cardiac insufficiency at follow-up in elderly patients with acute myocardial infarction

BACKGROUND

Impairment of cardiac function progresses after acute myocardial infarction (AMI). Lactate dehydrogenase (LDH), a marker of cardiac injury and an enzyme in anaerobic glycolysis, is suggested as a risk factor for patient mortality in inflammatory diseases.

METHODS

In this study, 448 older and 445 younger AMI patients were recruited and followed up. The effect of baseline serum LDH on post-infarction cardiac function was assessed at follow-up.

RESULTS

Elderly patients in the high baseline LDH group had a high risk of being diagnosed with cardiac insufficiency during follow-up (adjusted hazard ratio: 3.643, P = 0.007), and the follow-up left ventricular ejection fraction of the quartile subgroup tended to decrease with increasing in baseline serum LDH (adjusted odds ratio: 1.301, P = 0.001) for each 100 U/L increase. The LVDd and LVVd of elderly patients in the high LDH group were not significantly different from those of patients in the normal LDH group at baseline but were further increased in the high LDH group at follow-up. In younger patients, the effect of LDH on post-infarction cardiac structure and function was similar to that in older patients, but unlike older patients, Cox regression analysis showed that LDH was not the predominant influence.

CONCLUSION

Longitudinal changes in cardiac function were independently associated with high baseline serum LDH levels in patients with AMI. Baseline LDH levels are superior to other myocardial injury markers and may be a useful parameter in predicting future cardiac dysfunction after AMI, especially in the elderly.