CD8+ Regulatory T Cells Induced by Lipopolysaccharide Improve Mouse Endotoxin Shock.

Sepsis is a systemic inflammatory disease caused by a bacterial infection that leads to severe mortality, especially in elderly patients, because of an excessive immune response and impaired regulatory functions. Antibiotic treatment is widely accepted as the first-line therapy for sepsis; however, its excessive use has led to the emergence of multidrug-resistant bacteria in patients with sepsis. Therefore, immunotherapy may be effective in treating sepsis. Although CD8+ regulatory T cells (Tregs) are known to have immunomodulatory effects in various inflammatory diseases, their role during sepsis remains unclear. In this study, we investigated the role of CD8+ Tregs in an LPS-induced endotoxic shock model in young (8-12 wk old) and aged (18-20 mo old) mice. The adoptive transfer of CD8+ Tregs into LPS-treated young mice improved the survival rate of LPS-induced endotoxic shock. Moreover, the number of CD8+ Tregs in LPS-treated young mice increased through the induction of IL-15 produced by CD11c+ cells. In contrast, LPS-treated aged mice showed a reduced induction of CD8+ Tregs owing to the limited production of IL-15. Furthermore, CD8+ Tregs induced by treatment with the rIL-15/IL-15Rα complex prevented LPS-induced body wight loss and tissue injury in aged mice. In this study, to our knowledge, the induction of CD8+ Tregs as novel immunotherapy or adjuvant therapy for endotoxic shock might reduce the uncontrolled immune response and ultimately improve the outcomes of endotoxic shock.

D­allose enhances the efficacy of hydroxychloroquine against Lewis lung carcinoma cell growth by inducing autophagy.

Various cancer cells require massive amounts of glucose as an energy source for their dysregulated growth. Although D­allose, a rare sugar, inhibits tumor cell growth via inhibition of glucose uptake, a few cells can survive after treatment. However, the mechanism by which D­allose­resistant cells are generated remains unclear. Here, we investigated the properties of D­allose­resistant cells and evaluated the efficacy of combined treatment with this rare sugar and antitumor drugs. To this end, we established a D­allose­resistant tumor cell line and prepared a C57BL/6J mouse tumor xenograft model using Lewis lung carcinoma (LLC) cells. Xenograft­bearing mice were treated with D­allose (9 g/kg) and/or hydroxychloroquine (HCQ, 60 mg/kg), an autophagy inhibitor, for two weeks. Although D­allose inhibited LLC cell growth in a dose­dependent manner, a few cells survived. The upregulation of LC3­II, a classical autophagy marker, and the downregulation of mTOR and its downstream molecule Beclin1 were observed in established D­allose­resistant LLC cells, which were more sensitive to cell death induced by HCQ. Similarly, in the tumor xenograft model, the tumor volume in mice co­treated with D­allose and HCQ was considerably smaller than that in untreated or HCQ­treated mice. Importantly, the administration of D­allose induced autophagy selectively at the tumor site of the xenograft­bearing mice. These results provide a new therapeutic strategy targeting autophagy which is induced in tumor cells by D­allose administration, and may be used to improve therapies for lung cancer.

Viability of diffuse large B-cell lymphoma cells is regulated by kynurenine 3-monooxygenase activity.

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy that is the most common type of lymphoma in Japan. Previous studies have demonstrated that patients with DLBCL have a poor prognosis due to increased levels of indoleamine 2,3-dioxygnase and kynurenine (KYN). However, the roles of metabolites acting downstream of KYN and associated enzymes are not fully understood. The present study investigated the role of kynurenine 3-monooxygenase (KMO), which catalyzes the conversion of KYN to 3-hydroxykynurenine (3-HK), using serum samples from patients with DLBCL and human DLBCL cell lines with different KMO expression [STR-428 cells with high levels of KMO expression (KMOhigh) and KML-1 cells with low levels of KMO expression (KMOlow)]. Serum samples from 28 patients with DLBCL and 34 healthy volunteers were used to investigate the association between prognosis and KMO activity or 3-HK levels. Furthermore, to investigate the roles of KMO and its related metabolites, STR-428 and KML-1 cell lines, and the lymph nodes of patients with DLBCL were analyzed by reverse transcription-quantitative PCR for KMO, KYNU, 3-hydroxyanthranilate-3,4-dioxygenase and quinolinate phosphoribosyltransferase, by western blotting, and immunohistochemical or immunofluorescence staining for KMO, and by cell viability and NAD+/NADH assays. KYN pathway metabolites in serum samples were measured by HPLC. Serum 3-HK levels were regulated independently of serum KYN levels, and increased serum 3-HK levels and KMO activity were found to be associated with worse disease progression. Notably, the addition of KMO inhibitors and 3-HK negatively and positively regulated the viability of DLBCL cells, respectively. Furthermore, NAD+ levels in KMOhigh STR-428 cells were significantly higher than those in KMOlow KML-1 cells. These results suggested that 3-HK generated by KMO activity may be involved in the regulation of DLBCL cell viability via NAD+ synthesis.

Kynurenine produced by indoleamine 2,3-dioxygenase 2 exacerbates acute liver injury by carbon tetrachloride in mice.

Kynurenine (Kyn) plays an important role as an immune check-point molecule and regulates various immune responses through its aryl hydrocarbon receptor (Ahr). Kyn is synthesized by indoleamine 2,3-dioxygenase (Ido) and tryptophan 2,3-dioxygenase (Tdo). Ido contributes approximately 90% of tryptophan catabolism. Although Kyn is increased in various liver disorders, the roles of Kyn in liver injury are complicated because Ido1, Ido2, and Tdo are activated in different cell types. In this study, the roles of Ido2 in carbon tetrachloride (CCl4; 1 ml/kg, i.p.)-induced acute liver injury were examined using Ido2 knockout mice and Ido2 inhibitor. After CCl4 treatment, the ratio of Kyn to tryptophan and levels of Kyn in the liver were increased, accompanied by activation of Ahr-mediated signaling, as revealed by increased nuclear Ahr and Cyp1a1 mRNA. Knockout of Ido2 (Ido2-/-) and treatment with Ido2 inhibitor 1-methyl-D-tryptophan (D-1MT; 100 mg/kg, i.p.) attenuated CCl4-induced liver injury, with decreased induction of Ahr-mediated signaling. Administration of D-Kyn (100 mg/kg, i.p.) to Ido2-/- mice canceled the effect of Ido2 deficiency and exacerbated acute liver damage by CCl4 treatment. In addition, liver fibrosis induced by repeated CCl4 administration was suppressed in Ido2-/- mice. In conclusion, the action of Ido2 and Kyn in the liver may prevent severe hepatocellular damage and liver fibrosis.