THU0219 THE INVOLVEMENT OF MITOCHONDRIAL ACTIVATION VIA GLUTAMINOLYSIS IN HUMAN B CELL DIFFERENTIATION AND ITS RELEVANCE TO THE PATHOGENESIS OF SLE
Authors: Maiko Hajime, Shigeru Iwata, Mingzeng Zhang, Hiroko Miyata, Seunghyun Lee, Shingo Nakayamada, Kazuo Yamamoto, Yosuke Okada, Yoshiya Tanaka
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> B cells play a crucial role in Systemic Lupus Erythematosus (SLE). Recently, "Immunometabolism" attract much attention. Glucose and glutamine are important nutrition for energy production such as ATP in various cells. It has been reported that aerobic glycolysis, glutaminolysis and mitchondrial functions enhanced in cancer cells. However, the involvement of metabolic reprograming in plasmablast differentiation and its relevance to the pathogenesis of SLE remained elusive. <h3>Objectives</h3> We first investigated the abnormality of mitochondria in B cells from patients with SLE by flow cytometry. Next, B cells were isolated from healthy donors (HDs) and metabolic reprograming were assessed in vitro. <h3>Methods</h3> First, peripheral blood mononuclear cells (PBMCs) were obtained from age-matched 31 HDs and 29 patients with SLE. The mitochondrial membrane potential was measured with DiOc6 by flow cytometry. In addition, CD19<sup>+</sup> cells were isolated from HDs and stimulated with CpG (TLR9 ligand) and IFN-α. Change of aerobic glycolysis, glutaminolysis and mitochondrial functions were assessed in the absence of glucose or glutamine and in the addition of metformine, which is known as AMPK activator, in vitro. <h3>Results</h3> We first examined the abnormality of mitochondria in B cells from patients with SLE using DiOc6 as a marker of depolarization-activated mitochondrial membrane. Baseline characteristics of SLE were males: females=1:28, age 40.2 years, disease duration 132.2 months, SLEDAI 6.4 and BILAG 6.2 at the timing of admission due to exacerbation of SLE. The percentage of IgD<sup>-</sup>CD27<sup>-</sup> memory B cells were higher than those of HDs, while the percentage of IgM memory B cells were lower than that of HDs. The percentage of CD24<sup>-</sup>DiOc6<sup>+</sup> cells in IgD<sup>-</sup>CD27<sup>-</sup> memory B cells from patients with SLE were higher than that of HDs. These results indicate that B cells from patients with SLE have the abnormality of differentiation and mitochondrial functions. Next, we assessed the change of aerobic glycolysis, mitochondrial functions and glutaminolysis in the process of plasmablast differentiation in vitro. Stimulation with CpG and IFN-α, 1) enhanced aerobic glycolysis, which was assessed by lactate production. 2) increased the area of cytoplasm including many expanded mitochondrial cristae with slightly wider and loosely organized intermembrane space in electric microscopy, accompanied with ROS production and DiOc6 up-regulation, 3) induced CD27<sup>hi</sup>CD38<sup>hi</sup> plasmablasts differentiation and immunoglobulin production. Lactate production was decreased in the absence of both glucose or glutamine. ROS production and DiOc6 expression were decreased in the absence of glutamine, leading to inhibition of plasmablasts differentiation and immunoglobulin production. On the other hand, this tendency was not shown in the absence of glucose. Next, we evaluated oxygen consumption rate (OCR). OCR was also suppressed in the absence of glutamine. Metformin, abrogated glutamine uptake, resulting in suppression of ROS production, DiOc6 expression, plasmablast differentiation and immunoglobulin production. <h3>Conclusion</h3> These results suggest that mitochondrial activation via glutaminolysis may play an important role in the differentiation from IgD<sup>-</sup>CD27<sup>-</sup> double negative B cells to plasmablasts and production of immunoglobulins in patients with SLE. <h3>Disclosure of Interests</h3> Maiko Hajime: None declared, Shigeru Iwata: None declared, Mingzeng Zhang: None declared, Hiroko Miyata: None declared, SEUNGHYUN LEE: None declared, Shingo Nakayamada Grant/research support from: Mitsubishi-Tanabe, Takeda, Novartis and MSD, Speakers bureau: Bristol-Myers, Sanofi, Abbvie, Eisai, Eli Lilly, Chugai, Asahi-kasei and Pfizer, Kazuo Yamamoto: None declared, Yosuke Okada: None declared, Yoshiya Tanaka Grant/research support from: Abbvie, Astellas, Bristol-Myers Squibb, Chugai, Daiichi-Sankyo, Eisai, Mitsubishi-Tanabe, MSD, Ono, Taisho-Toyama, Takeda, Speakers bureau: Abbvie, Asahi-kasei, Astellas, Bristol-Myers Squibb, Chugai, Daiichi-Sankyo, Eli Lilly, Eisai, Glaxo-Smithkline, Janssen, Mitsubishi-Tanabe, Novartis, Pfizer Japan Inc, Sanofi, Takeda, UCB, YL Biologics