Intravenous Arginine Administration Benefits CD4+ T-Cell Homeostasis and Attenuates Liver Inflammation in Mice with Polymicrobial Sepsis

Immunogenic shift of arginine metabolism triggers systemic metabolic and immunological reprogramming to prevent HER2+ breast cancer

Arginine metabolism in tumors is often shunted into the pathway producing pro-tumor and immune suppressive polyamines (PAs), while downmodulating the alternative nitric oxide (NO) synthesis pathway. Aiming to correct arginine metabolism in tumors, arginine deprivation therapy and inhibitors of PA synthesis have been developed. Despite some therapeutic advantages, these approaches have often yielded severe side effects, making it necessary to explore an alternative strategy. We previously reported that supplementing SEP, the endogenous precursor of BH4 (the essential NO synthase cofactor), could correct arginine metabolism in tumor cells and tumor-associated macrophages (TAMs) and induce their metabolic and phenotypic reprogramming. We saw that oral SEP treatment effectively suppressed the growth of HER2-positive mammary tumors in animals. SEP also has no reported dose-dependent toxicity in clinical trials for metabolic disorders. In the present study, we report that a long-term use of SEP in animals susceptible to HER2-positive mammary tumors effectively prevented tumor occurrence. These SEP-treated animals had undergone reprogramming of the systemic metabolism and immunity, elevating total T cell counts in the circulation and bone marrow. Given that bone marrow-resident T cells are mostly memory T cells, it is plausible that chronic SEP treatment promoted memory T cell formation, leading to a potent tumor prevention. These findings suggest the possible roles of the SEP/BH4/NO axis in promoting memory T cell formation and its potential therapeutic utility for preventing HER2-positive breast cancer.

Th17/Treg balance: the bloom and wane in the pathophysiology of sepsis

Sepsis is a multi-organ dysfunction characterized by an unregulated host response to infection. It is associated with high morbidity, rapid disease progression, and high mortality. Current therapies mainly focus on symptomatic treatment, such as blood volume supplementation and antibiotic use, but their effectiveness is limited. Th17/Treg balance, based on its inflammatory property, plays a crucial role in determining the direction of the inflammatory response and the regression of organ damage in sepsis patients. This review provides a summary of the changes in T-helper (Th) 17 cell and regulatory T (Treg) cell differentiation and function during sepsis, the heterogeneity of Th17/Treg balance in the inflammatory response, and the relationship between Th17/Treg balance and organ damage. Th17/Treg balance exerts significant control over the bloom and wanes in host inflammatory response throughout sepsis.

Potential therapeutic implications of calcitriol administration and weight reduction on CD4 T cell dysregulation and renin angiotensin system-associated acute lung injury in septic obese mice

This study investigated the effects of weight reduction and/or calcitriol administration on regulating CD4 T cell subsets and renin-angiotensin system (RAS)-associated acute lung injury (ALI) in obese mice with sepsis. Half of the mice were fed a high-fat diet for 16 weeks, half of them had high-fat diet for 12 weeks then were transferred to a low-energy diet for 4 weeks. After feeding the respective diets, cecal ligation and puncture (CLP) were performed to induce sepsis. There were four sepsis groups: OSS group, obese mice injected with saline; OSD group, obese mice given calcitriol; WSS group, mice with weight reduction and saline; WSD group, mice with weight reduction and calcitriol. Mice were sacrificed after CLP. The findings showed that CD4 T subsets distribution did not differ among the experimental groups. Calcitriol-treated groups had higher RAS-associated AT2R, MasR, ACE2, and angiopoietin 1-7 (Ang(1-7)) levels in the lungs. Also, higher tight junction proteins were noted 12 h after CLP. At 24 h post-CLP, weight reduction and/or calcitriol treatment reduced plasma inflammatory mediator production. Calcitriol-treated groups had higher CD4/CD8, T helper (Th)1/Th2 and lower Th17/regulatory T (Treg) ratios than the groups without calcitriol. In the lungs, calcitriol-treated groups had lower AT1R levels, whereas the RAS anti-inflammatory protein levels were higher than those groups without calcitriol. Lower injury scores were also noted at this time point. These findings suggested weight reduction decreased systemic inflammation. However, calcitriol administration produced a more-balanced Th/Treg distribution, upregulated the RAS anti-inflammatory pathway, and attenuated ALI in septic obese mice.

Amino acid metabolism in immune cells: essential regulators of the effector functions, and promising opportunities to enhance cancer immunotherapy

Amino acids are basic nutrients for immune cells during organ development, tissue homeostasis, and the immune response. Regarding metabolic reprogramming in the tumor microenvironment, dysregulation of amino acid consumption in immune cells is an important underlying mechanism leading to impaired anti-tumor immunity. Emerging studies have revealed that altered amino acid metabolism is tightly linked to tumor outgrowth, metastasis, and therapeutic resistance through governing the fate of various immune cells. During these processes, the concentration of free amino acids, their membrane bound transporters, key metabolic enzymes, and sensors such as mTOR and GCN2 play critical roles in controlling immune cell differentiation and function. As such, anti-cancer immune responses could be enhanced by supplement of specific essential amino acids, or targeting the metabolic enzymes or their sensors, thereby developing novel adjuvant immune therapeutic modalities. To further dissect metabolic regulation of anti-tumor immunity, this review summarizes the regulatory mechanisms governing reprogramming of amino acid metabolism and their effects on the phenotypes and functions of tumor-infiltrating immune cells to propose novel approaches that could be exploited to rewire amino acid metabolism and enhance cancer immunotherapy.

Discovery of metabolic markers for the discrimination of Helwingia species based on bioactivity evaluation, plant metabolomics, and network pharmacology

RATIONALE

Helwingia japonica (HJ), a traditional medicinal plant, is commonly used for the treatment of dysentery, blood in the stool, and scald burns. Three major HJ species, Helwingia japonica (Thunb.) Dietr. (QJY), Helwingia himalaica Hook. f. et Thoms. ex C. B. Clarke, and Helwingia chinensis Batal., share great similarities in both morphology and chemical constituents. The discrimination of medicinal plants directly affects their pharmacological and clinical effects. Here, we solved the taxonomy uncertainty of these three HJ species and explored the discrimination and study of other traditional medicines (TMs).

METHODS

First, the anti-inflammatory effects of the three HJ species were compared using lipopolysaccharide (LPS)-induced inflammatory responses in mouse leukemia cells of monocyte macrophage (RAW) 264.7 cells. Then, plant metabolomics were performed in 48 batches of samples to discover chemical markers for discriminating different HJ species. Finally, network pharmacology was applied to explore the linkages among constituents, targets, and signaling pathways.

RESULTS

In vitro experiments showed that the QJY exhibited the most potential anti-inflammatory activities. Meanwhile, 172 compounds were tentatively identified and eight metabolites with higher relative content in QJY were designated as chemical markers to distinguish QJY and the other two species. According to the property of absorbed in vivo, threonic acid, arginine, and tyrosine were selected to construct a component-target-pathway network. The network pharmacology analysis confirmed that the chemotaxonomy differentiation was consistent with the bioactive assessment.

CONCLUSIONS

The present study demonstrates that bioactivity evaluation integrated with plant metabolomics and network pharmacology could be used as an effective approach to discriminate different TMs and discover the active compounds.

Protective effect of endothelial progenitor cell-derived exosomal microRNA-382-3p on sepsis-induced organ damage and immune suppression in mice

OBJECTIVE

To explore the role of endothelial progenitor cell (EPC)-derived exosomal microRNA-382-3p (miR-382-3p) in septic injury in mice.

METHODS

A murine model of sepsis was introduced by cecal ligation and puncture (CLP). The model mice were treated with EPC-derived exosomes (Exos). The lung, kidney and liver tissues of mice were collected and stained with hematoxylin and eosin. The lymphocytes in murine spleen tissues, and the proportion and phenotype of the T helper cells (Ths) were examined by flow cytometry. The exosomal miRNAs were screened using a microarray analysis. The expressions of miR-382-3p and beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC) were measured to explore possible mechanism of Exos in septic injury in mice.

RESULTS

EPC-derived Exos alleviated CLP-induced tissue damage in the lung, kidney and liver tissues in septic mice. They also restored the number of lymphocytes and the concentration of Ths, and reduced the imbalance in Th1 and Th2 cells in mice. The Exos mainly contained miR-382-3p, and miR-382-3p directly targeted BTRC mRNA. Either downregulation of miR-382-3p or upregulation of BTRC blocked the protective roles of Exos in septic injury and immune suppression. Overexpression of BTRC increased the phosphorylation of nuclear factor kappa B (NF-κB) inhibitor α (IκBα) and NF-κB.

CONCLUSION

EPC-derived exosomal miR-382-3p alleviates sepsis-induced organ damage and immune suppression in septic mice through regulating BTRC and the IκBα/NF-κB axis.

Combating hematopoietic and hepatocellular abnormalities resulting from administration of cisplatin: Role of liver targeted glycyrrhetinic acid nanoliposomes loaded with amino acids

The effectiveness of cisplatin in cancer treatment renders its use vital to clinicians. However, the accompanying side effects as cachexia, emesis and liver damage necessitate the use of a dietary supplement which is capable of hindering such undesirable complications. The branched chain amino acids as well as glutamine and arginine have been proven to be effective nutritional co-adjuvant therapeutic agents. Furthermore, new pharmaceutical approaches encompass designing organ-targeted nanoformulations to increase the medicinal efficacy. Therefore, the aim of the present study was to investigate the beneficial effects of liver-targeted amino acids-loaded nanoliposomes in counteracting the adverse hematopoietic and hepatic complications associated with cisplatin. Results revealed the use of the combination of two nanoliposomal formulations (one loading leucine + isolecuine + valine, and the other loading glutamine and arginine) given orally at a dose of 200 mg/kg for twelve days was effective against cisplatin-induced toxicities represented by improvement in the complete blood picture parameters, decrease in the serum hepatic enzymes levels, amelioration of the hepatic oxidative stress and cellular energy imbalance along with reduction in the histopathological abnormalities. It can be concluded that amino acids loaded nanoliposomes could be considered a new strategy in preventing cisplatin's adverse effects.

Inhibition of endoplasmic reticulum stress and the downstream pathways protects CD4+ T cells against apoptosis and immune dysregulation in sepsis

BACKGROUND

Immunosuppression mediated by CD4⁺ T cell apoptosis and dysfunction is a key factor in promoting the progression of sepsis. Endoplasmic reticulum (ER) stress participates in the apoptosis and dysfunction of immune cells.

AIM

We aimed to investigate the role of ER stress inhibition in CD4⁺ T cells in both in vitro and in vivo models of sepsis.

METHODS

In vitro model of sepsis was established with lipopolysaccharide (LPS) and the rat model of sepsis was established using cecal ligation and puncture (CLP). After the LPS treatment or CLP, ER stress inhibitors including 4-PBA, SNJ-1945, and SP600125 were used to treat cells or rats, and the CD4⁺ T cells were obtained by magnetic bead sorting. The effects of ER stress inhibitors on apoptosis and the function of CD4⁺ T cells were evaluated.

RESULTS

After the LPS stimulation or CLP, the levels of ER stress and downstream markers (PERK, eIF2α, IRE-1α, ATF6, ATF4, XBP-1s, GRP78, CHOP, and p-JNK) were increased in CD4⁺ T cells at the beginning of sepsis. Meanwhile, the number of apoptotic CD4⁺ T cells markedly increased. In addition, sepsis impaired the function of CD4⁺ T cells, manifested by the increased population of Th1, Th2, Th17, and Treg, as well as the production of TNF-α, interleukin (IL)-6, IL-4, and IL-10. However, inhibitors of ER stress, JNK, and calpain all decreased the induction of Th1 and Th17, enhanced the increase of Th2 and Treg, decreased the production of TNF-α and IL-6, and enhanced the production of IL-4 and IL-10.

CONCLUSION

Our findings indicate that ER stress inhibitors may play a protective role by reducing CD4⁺ T cell apoptosis and maintaining CD4⁺ T cell function, which may be useful for enhancing the immune function and poor prognosis of patients with sepsis.

Insight Into Regulatory T Cells in Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a diffuse central nervous system (CNS) dysfunction during sepsis, and is associated with increased mortality and poor outcomes in septic patients. Despite the high incidence and clinical relevance, the exact mechanisms driving SAE pathogenesis are not yet fully understood, and no specific therapeutic strategies are available. Regulatory T cells (T_regs) have a role in SAE pathogenesis, thought to be related with alleviation of sepsis-induced hyper-inflammation and immune responses, promotion of T helper (Th) 2 cells functional shift, neuroinflammation resolution, improvement of the blood-brain barrier (BBB) function, among others. Moreover, in a clinical point of view, these cells have the potential value of improving neurological and psychiatric/mental symptoms in SAE patients. This review aims to provide a general overview of SAE from its initial clinical presentation to long-term cognitive impairment and summarizes the main features of its pathogenesis. Additionally, a detailed overview on the main mechanisms by which T_regs may impact SAE pathogenesis is given. Finally, and considering that T_regs may be a novel target for immunomodulatory intervention in SAE, different therapeutic options, aiming to boost peripheral and brain infiltration of T_regs, are discussed.

Regulatory T Cells: Angels or Demons in the Pathophysiology of Sepsis?

Sepsis is a syndrome characterized by life-threatening organ dysfunction caused by the dysregulated host response to an infection. Sepsis, especially septic shock and multiple organ dysfunction is a medical emergency associated with high morbidity, high mortality, and prolonged after-effects. Over the past 20 years, regulatory T cells (Tregs) have been a key topic of focus in all stages of sepsis research. Tregs play a controversial role in sepsis based on their heterogeneous characteristics, complex organ/tissue-specific patterns in the host, the multi-dimensional heterogeneous syndrome of sepsis, the different types of pathogenic microbiology, and even different types of laboratory research models and clinical research methods. In the context of sepsis, Tregs may be considered both angels and demons. We propose that the symptoms and signs of sepsis can be attenuated by regulating Tregs. This review summarizes the controversial roles and Treg checkpoints in sepsis.

FGF15 Protects Septic Mice by Inhibiting Inflammation and Modulating Treg Responses

Background

Fibroblast growth factor 15 (FGF15) through its FGF-receptor (FGFR)-4 inhibits hepatic inflammation. The current study aimed at investigating whether FGF15 could inhibit septic inflammation and its compensative regulatory T cell (Treg) responses in a mouse sepsis model of cecal ligation and puncture (CLP) and in vitro transwell co-culture.

Methods

Following the sham or CLP procedure, male CLP C57BL/6 mice were intravenously injected with vehicle saline or FGF15 beginning at 2 h post the procedure every 12 h for three days. Some mice were euthanized and their serum and liver samples were collected for examination of cytokines and Tregs by enzyme-linked immunosorbent assay (ELISA), Western blot and flow cytometry. The remaining mice were monitored for their survival up to 14 days post procedure. Moreover, the purified hepatic CD4+ T cells were co-cultured in transwell plates with unmanipulated NCTC 1469 cells or the cells that had been transfected with the control or FGFR4-specific siRNA and treated with, or without, Lipopolysaccharides (LPS) for 24 h, followed by treatment with vehicle PBS or FGF15 for 48 h.

Results

Compared with the CLP group of mice, treatment with FGF15 significantly prolonged the mean survival days of mice (12 vs 1.17 in the CLP group, P = 0.022), mitigated hepatic inflammation and reduced the frequency of apoptotic cells in the liver of mice. FGF15 treatment decreased the percentages of hepatic Tregs, hepatic IL-2, TGF-β and FOXP3 expression in septic mice, accompanied by decreasing serum IL-1β, TNF-α, IL-6 and IL-10 levels. Similarly, FGF15 treatment also attenuated the LPS-increased frequency of Tregs, FOXP3 and IL-2 expression and IL-1β, TNF-α, IL-6 and IL-10 secretion in vitro after co-culture with NCTC 1469 cells, but not co-cultured FGFR4-silenced NCTC 1649 cells.

Conclusion

FGF15 treatment through FGFR4 ameliorated hepatic inflammation and its compensative Treg responses, which were associated with protecting from septic death in mice.