Protein arginine N-methyltransferase 4 (PRMT4) contributes to lymphopenia in experimental sepsis

PRMT4 Reduced Erastin-Induced Ferroptosis in Nasopharyngeal Carcinoma Cisplatin-Resistant Cells by Nrf2/GPX4 Pathway

Nasopharyngeal carcinoma (NPC) is one of the common malignant tumors in clinic. In the current study, we aim to investigate the effects of PRMT4 on erastin-induced ferroptosis in NPC by cisplatin resistant. PRMT4 expression in patients with NPC by cisplatin was upregulated. PRMT4 upregulation promoted cell growth of erastin-induced ferroptosis in NPC cisplatin-resistant cells. PRMT4 downregulation reduced cell growth of erastin-induced ferroptosis in NPC cisplatin-resistant cells. PRMT4 promoted tumor volume in mice model of erastin-induced NPC by cisplatin. PRMT4 upregulation reduced erastin-induced ferroptosis in NPC cisplatin-resistant cells by mitochondrial damage. PRMT4 upregulation induced Nrf2 protein expression in model of erastin-induced NPC by cisplatin. Nrf2 reduced the effects of si-PRMT4 on cell growth of erastin-induced ferroptosis in NPC cisplatin-resistant cells. Nrf2 inhibitor reduced the effects of PRMT4 on cell growth of erastin-induced ferroptosis in NPC cisplatin-resistant cells. Nrf2 reduced the effects of si-PRMT4 on erastin-induced ferroptosis in NPC cisplatin-resistant cells by mitochondrial damage. PRMT4 protein interlinked with Nrf2 protein to decrease Nrf2 ubiquitination. Methylation increased PRMT4 DNA stability. Collectively, our data reveal that PRMT4 reduced erastin-induced ferroptosis in NPC cisplatin-resistant cells by Nrf2/GPX4 pathway, suggesting that targeting PRMT4 may present as a potential strategy against the development of NPC.

Lymphopenia in sepsis: a narrative review

This narrative review provides an overview of the evolving significance of lymphopenia in sepsis, emphasizing its critical function in this complex and heterogeneous disease. We describe the causal relationship of lymphopenia with clinical outcomes, sustained immunosuppression, and its correlation with sepsis prediction markers and therapeutic targets. The primary mechanisms of septic lymphopenia are highlighted. In addition, the paper summarizes various attempts to treat lymphopenia and highlights the practical significance of promoting lymphocyte proliferation as the next research direction.

Risk factors for prolonged infection and secondary infection in pediatric severe sepsis

PURPOSE

Sepsis causes significant worldwide morbidity and mortality. Inability to clear an infection and secondary infections are known complications in severe sepsis and likely result in worsened outcomes. We sought to characterize risk factors of these complications.

METHODS

We performed a secondary analysis of clinical data from 401 subjects enrolled in the PHENOtyping sepsis-induced Multiple organ failure Study. We examined factors associated with prolonged infection, defined as infection that continued to be identified 7 days or more from initial identification, and secondary infection, defined as new infections identified ≥ 3 days from presentation. Multivariable adjustment was performed to examine laboratory markers of immune depression, with immunocompromised and immunocompetent subjects analyzed separately.

RESULTS

Illness severity, immunocompromised status, invasive procedures, and site of infection were associated with secondary infection and/or prolonged infection. Persistent lymphopenia, defined as an absolute lymphocyte count (ALC) < 1000 cells/µL twice in the first five days, and persistent neutropenia, defined as absolute neutrophil count (ANC) < 1000 cells/µL twice in the first five days, were associated with secondary and prolonged infections. When adjusted in multivariable analysis, persistent lymphopenia remained associated with secondary infection in both immunocompromised (aOR = 14.19, 95% CI [2.69, 262.22] and immunocompetent subjects (aOR = 2.09, 95% CI [1.03, 4.17]). Persistent neutropenia was independently associated with secondary infection in immunocompromised subjects (aOR = 5.34, 95% CI [1.92, 15.84]). Secondary and prolonged infections were associated with worse outcomes, including death.

CONCLUSIONS

Laboratory markers of immune suppression can be used to predict secondary infection. Lymphopenia is an independent risk factor in immunocompromised and immunocompetent patients for secondary infection.

Epigenetic mechanisms of Immune remodeling in sepsis: targeting histone modification

Sepsis is a life-threatening disorder disease defined as infection-induced dysregulated immune responses and multiple organ dysfunction. The imbalance between hyperinflammation and immunosuppression is a crucial feature of sepsis immunity. Epigenetic modifications, including histone modifications, DNA methylation, chromatin remodeling, and non-coding RNA, play essential roles in regulating sepsis immunity through epi-information independent of the DNA sequence. In recent years, the mechanisms of histone modification in sepsis have received increasing attention, with ongoing discoveries of novel types of histone modifications. Due to the capacity for prolonged effects on immune cells, histone modifications can induce immune cell reprogramming and participate in the long-term immunosuppressed state of sepsis. Herein, we systematically review current mechanisms of histone modifications involved in the regulation of sepsis, summarize their role in sepsis from an immune perspective and provide potential therapeutic opportunities targeting histone modifications in sepsis treatment.

Protein Arginine Methyltransferases as Therapeutic Targets in Hematological Malignancies

Arginine methylation is a common post-translational modification affecting protein activity and the transcription of target genes when methylation occurs on histone tails. There are nine protein arginine methyltransferases (PRMTs) in mammals, divided into subgroups depending on the methylation they form on a molecule of arginine. During the formation and maturation of the different types of blood cells, PRMTs play a central role by controlling cell differentiation at the transcriptional level. PRMT enzymatic activity is necessary for many cellular processes in hematological malignancies, such as the activation of cell cycle and proliferation, inhibition of apoptosis, DNA repair processes, RNA splicing, and transcription by methylating histone tails' arginine. Chemical tools have been developed to inhibit the activity of PRMTs and have been tested in several models of hematological malignancies, including primary samples from patients, xenografts into immunodeficient mice, mouse models, and human cell lines. They show a significant effect by reducing cell viability and increasing the overall survival of mice. PRMT5 inhibitors have a strong therapeutic potential, as phase I clinical trials in hematological malignancies that use these molecules show promising results, thus, underlining PRMT inhibitors as useful therapeutic tools for cancer treatment in the future.

The Influence of Arginine Methylation in Immunity and Inflammation

Exploration in the field of epigenetics has revealed that protein arginine methyltransferases (PRMTs) contribute to disease, and this has given way to the development of specific small molecule compounds that inhibit arginine methylation. Protein arginine methylation is known to regulate fundamental cellular processes, such as transcription; pre-mRNA splicing and other RNA processing mechanisms; signal transduction, including the anti-viral response; and cellular metabolism. PRMTs are also implicated in the regulation of physiological processes, including embryonic development, myogenesis, and the immune system. Finally, the dysregulation of PRMTs is apparent in cancer, neurodegeneration, muscular disorders, and during inflammation. Herein, we review the functions of PRMTs in immunity and inflammation. We also discuss recent progress with PRMTs regarding the modulation of gene expression related to T and B lymphocyte differentiation, germinal center dynamics, and anti-viral signaling responses, as well as the clinical relevance of using PRMT inhibitors alone or in combination with other drugs to treat cancer, immune, and inflammatory-related diseases.