In this issue, Zaver et al. report on MEK as a therapeutic target for restoring intercellular adhesion among epidermal keratinocytes and potentially reducing skin blistering in Darier disease. The cover image displays normal human skin stained to highlight proteins critical for epidermal integrity, including the desmosomal cadherin desmoglein 1 (yellow), which is linked to the keratin 10 cytoskeleton (magenta). Nuclei are stained with DAPI (cyan).
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with a dramatic sex bias, affecting 9-times more women than men. Activation of toll-like receptor 7 (TLR7) by self-RNA is a central pathogenic process leading to aberrant production of type-I interferon (IFN) in SLE, but the specific RNA molecules that serve as TLR7 ligands have not been defined. We therefore sought to identify female-specific endogenous RNAs containing canonical TLR7 stimulatory motifs. By leveraging gene expression data and the known sequence specificity of TLR7, we identified the female-specific X-inactive specific transcript (XIST) long non-coding RNA as a uniquely rich source of TLR7 ligands in SLE. XIST RNA stimulated IFNα production by plasmacytoid DCs in a TLR7-dependent manner, and deletion of XIST diminished the ability of whole cellular RNA to activate TLR7. XIST levels were elevated in blood leukocytes from female SLE patients compared to controls, correlated positively with disease activity and the IFN signature, and were enriched in extracellular vesicles released from dying cells in vitro. Importantly, XIST was not IFN-inducible, suggesting that XIST is a driver, rather than a consequence of IFN in SLE. Our work suggests a novel role for XIST RNA as a female-specific danger signal underlying the sex bias in SLE.
Jonathan D. Crawford, Hong Wang, Daniela Trejo-Zambrano, Raffaello Cimbro, C. Conover Talbot Jr., Mekha A. Thomas, Ashley M. Curran, Alexander A. Girgis, John T. Schroeder, Andrea Fava, Daniel W. Goldman, Michelle Petri, Antony Rosen, Brendan Antiochos, Erika Darrah
Glycolysis is highly enhanced in Pancreatic ductal adenocarcinoma (PDAC) cells; thus, glucose restrictions are imposed on nontumor cells in the PDAC tumor microenvironment (TME). However, little is known about how such glucose competition alters metabolism and confers phenotypic changes in stromal cells in the TME. Here, we report that cancer-associated fibroblasts (CAFs) with restricted glucose availability utilize lactate from glycolysis-enhanced cancer cells as a fuel and exert immunosuppressive activity in the PDAC TME. The expression of lactate dehydrogenase A (LDHA), which regulates lactate production, was a poor prognostic factor for PDAC patients, and LDHA depletion suppressed tumor growth in a CAF-rich murine PDAC model. Coculture of CAFs with PDAC cells revealed that most of the glucose was taken up by the tumor cells and that CAFs consumed lactate via monocarboxylate transporter 1 to enhance proliferation through the TCA cycle. Moreover, lactate-stimulated CAFs upregulated IL6 expression and suppressed cytotoxic immune cell activity synergistically with lactate. Finally, the LDHA inhibitor FX11 reduced tumor growth and improved antitumor immunity in CAF-rich PDAC tumors. Our study provides new insights into crosstalk among tumor cells, CAFs, and immune cells mediated by lactate and offers therapeutic strategies for targeting LDHA enzymatic activity in PDAC cells.
Fumimasa Kitamura, Takashi Semba, Noriko Yasuda-Yoshihara, Kosuke Yamada, Akiho Nishimura, Juntaro Yamasaki, Osamu Nagano, Tadahito Yasuda, Atsuko Yonemura, Yilin Tong, Huaitao Wang, Takahiko Akiyama, Kazuki Matsumura, Norio Uemura, Rumi Itoyama, Luke Bu, Lingfeng Fu, Xichen Hu, Feng Wei, Kosuke Mima, Katsunori Imai, Hiromitsu Hayashi, Yo-ichi Yamashita, Yuji Miyamoto, Hideo Baba, Takatsugu Ishimoto
A better understanding of the epitopes most relevant for antibody-mediated protection against tuberculosis (TB) remains a major knowledge gap. We have shown that human polyclonal IgG to the Mycobacterium tuberculosis (Mtb) surface glycan arabinomannan (AM) and related lipoarabinomannan (LAM) is protective against TB. To investigate the impact of AM epitope recognition and Fc-gamma receptor (FcgR)-binding on antibody functions against Mtb, we isolated a high-affinity human monoclonal antibody (mAb; P1AM25) to AM and show its binding to oligosaccharide (OS) motifs we previously found to be associated with in vitro functions of human polyclonal anti-AM IgG. Human IgG1 P1AM25, but not two other high-affinity human IgG1 anti-AM mAbs reactive with different AM OS motifs, enhanced Mtb phagocytosis by macrophages and reduced intracellular growth in an FcgR-dependent manner. P1AM25 in murine IgG2a, but neither murine IgG1 nor a non-FcgR-binding IgG, given intraperitoneally prior to and after aerosolized Mtb infection was protective in C57BL/6 mice. Moreover, we demonstrate the protective efficacy of human IgG1 P1AM25 in passive transfer with Mtb-infected FcgR-humanized mice. These data enhance our knowledge of the important interplay between both antibody epitope specificity and Fc effector functions in the defense against Mtb and could inform development strategies of vaccines against TB.
Yanyan Liu, Tingting Chen, Yongqi Zhu, Aisha Furey, Todd L. Lowary, John Chan, Stylianos Bournazos, Jeffrey V. Ravetch, Jacqueline M. Achkar
Abnormal macrophage polarization is generally present in autoimmune diseases. Overwhelming M1 macrophage activation promotes the continuous progression of inflammation, which is one of the vital reasons for the development of autoimmune diseases. However, the underlying mechanism is still unclear. Here we explore the function of RFX1 in macrophage polarization by constructing colitis and lupus-like mouse models. Both in vivo and in vitro experiments confirmed that RFX1 can promote M1 and inhibit M2 macrophage polarization. Besides, we also found that RFX1 promoted DNA demethylation of macrophage polarization-related genes by increasing APOBEC3A/Apobec3 expression. Noteworthily, we identified a potential RFX1 inhibitor, adenosine diphosphate (ADP), providing a potential strategy for treating autoimmune diseases.
Shuang Yang, Pei Du, Haobo Cui, Meiling Zheng, Wei He, Xiaofei Gao, Zhi Hu, Sujie Jia, Qianjin Lu, Ming Zhao
Aged skin is prone to viral infections, but the mechanisms responsible for this immunosenescent immune risk are unclear. We observed that aged murine and human skin expressed reduced antiviral proteins (AVPs) and circadian regulators including Bmal1 and Clock. Bmal1 and Clock were found to control rhythmic AVP expression in skin and such circadian-control of AVPs was diminished by disruption of immune cell interleukin 27 signaling and deletion of Bmal1/Clock genes in mouse skins, as well as siRNA-mediated knockdown of CLOCK in human primary keratinocytes. We found that treatment of circadian enhancing agents, nobiletin and SR8278, reduced infection of herpes simplex virus 1 (HSV1) in epidermal explants and human keratinocytes in a BMAL1/CLOCK-dependent manner. Circadian enhancing treatment also reversed susceptibility of aging murine skin and human primary keratinocytes to viral infection. These findings reveal an evolutionarily conserved and age-sensitive circadian regulation of cutaneous antiviral immunity, underscoring circadian restoration as an antiviral strategy in aging populations.
Stephen Kirchner, Vivian Lei, Paul T. Kim, Meera Patel, Jessica L. Shannon, David Corcoran, Dalton Hughes, Diana K. Waters, Kafui Dzirasa, Detlev Erdmann, Jörn Coers, Amanda S. MacLeod, Jennifer Y. Zhang