表皮プロテインC受容体が抗リン脂質抗体症候群の病態に関与する

抗カルジオリピン抗体 (aCL)や抗β2GPI抗体などの抗リン脂質抗体 (aPLs)の出現を特徴とする抗リン脂質抗体症候群 (APS)患者は、臨床的に動･静脈の血栓症、血小板減少症、習慣流産･死産･子宮内胎児死亡などを呈する難病で、原発性APSとともに、全身性エリテマトーデス (SLE)などの自己免疫疾患にしばしば合併することが知られています。APSにおける凝固亢進のメカニズムには不明な点が多く、aPLsがどのような抗原を認識するのかについての理解も進んでいないことが、APS治療法開発が進まない原因となっています。この論文で著者らは、endothelial protein C receptor (EPCR)がaPLsの標的となり、APSの病態に重要な役割を果たすことを明らかにしました。

EPCRは内皮細胞、骨髄細胞、胎盤のtrophoblastなどに発現が見られるCD1d様膜貫通糖タンパクであり、リン脂質と強固に結合します。正常状態ではホスファチジルコリンと結合したEPCRは抗凝固因子であるprotein Cを活性化しますが、EPCRは凝固開始因子tissue factor (TF)によるprotease-activated receptor 2 (PAR2)活性化にも関与し、TLR4の下流でtype I interferon (IFN) responseを誘導することも知られており、抗凝固のみならず凝固亢進、自己免疫反応にも関与する可能性が示されています。

主としてlate endsomeに発現するlysophosphatidic acid (LBPA)はEPCRと反応して複合体 (EPCR-LBPA)を形成することが知られていますが、著者らはaPLsがEPCR-LBPAを認識し、EPCR依存的にendosomeに輸送され、TLR7/8活性化を介してtype I IFN resposnseを誘導して組織炎症、凝固亢進、胎児死亡を誘導すること、そしてB1a細胞活性化によってaPLsの産生を促進することを明らかにしました。抗体によってEPCR-LBPA抑制、あるいは遺伝的にEPCRを欠損させることによりAPSモデルマウスの凝固亢進は抑制されました。またSLEモデルマウスにおけるaPLs産生もEPCR-LBPA抗体によって抑制されました。

これらの結果は、aPLsによるEPCR-LBPAの活性化がAPSのみならずSLEの病態に重要な役割を果たす可能性を示しています。新型コロナウイルス感染症においてもaPLsの出現と凝固亢進が報告されており、この病態におけるEPCR-LBPAの関与にも興味がもたれます。

Nadine Müller-Calleja et al., 

Lipid presentation by the protein C receptor links coagulation with autoimmunity.

Science  12 Mar 2021: Vol. 371, Issue 6534, eabc0956 DOI: 10.1126/science.abc0956

Lipid presentation by the protein C receptor links coagulation with autoimmunity

Several autoimmune diseases, including systemic lupus erythematosus and primary antiphospholipid syndrome, are characterized by the presence of antiphospholipid antibodies (aPLs). These molecules can activate the complement and coagulation cascades, which contributes to pathologies such as thrombosis, stroke, and pregnancy complications. Müller-Calleja et al. found that endothelial protein C receptor (EPCR) in complex with lysobisphosphatidic acid (LBPA) is the cell-surface target for aPL and mediates its internalization (see the Perspective by Kaplan). aPL binding to EPCR-LBPA resulted in the activation of tissue factor–mediated coagulation and interferon-α production by dendritic cells. Interferon-α, in turn, fueled the expansion of B1a cells, which secrete aPLs. The specific blockade of this target in mice inhibited the development of aPL autoimmunity, offering hope for future therapies for these conditions. Science , this issue p. [eaay1833][1]; see also p. [1100][2] ### INTRODUCTION Antiphospholipid antibodies (aPLs) transiently appear in infectious diseases but can persist in primary antiphospholipid syndrome (APS) or in association with other autoimmune diseases, including lupus erythematosus. Clinical manifestations of APS range from venous thrombosis and stroke to severe microangiopathic organ damage and pregnancy complications. The activation of coagulation and complement cascades is crucial for the pathogenic effects of aPLs as well as for their proinflammatory cell signaling in innate immune, vascular endothelial, and embryonic trophoblast cells. However, the diverse reactivity of aPLs with negatively charged lipids and with blood proteins has hampered the identification of the central mechanism(s) underlying aPL pathogenic signaling. ### RATIONALE Lipid-reactive aPLs sensitize innate immune cells to toll-like receptor 7 (TLR7) agonists and up-regulate the coagulation initiator tissue factor (TF). TF-dependent signaling by protease-activated receptor 2 (PAR2) involves the endothelial protein C receptor (EPCR, encoded by PROCR ), and this signaling complex specifically participates in interferon (IFN) responses downstream of TLR4. Because aPLs are potent inducers of IFN-α production by dendritic cells, we tested the hypothesis that EPCR contributes to APS pathologies and the development of aPL autoimmunity. ### RESULTS We found that EPCR serves as the cell surface receptor for aPLs and mediates aPL internalization following a previously delineated TF–integrin trafficking route in monocytes. Knock-in mutagenesis of the EPCR intracellular cysteine residue in Procr C/S mice abolishes aPL endosomal trafficking and aPL proinflammatory and IFN signaling in innate immune cells. We show that these mutant mice have a defect in the ability to exchange phosphatidylcholine structurally bound to EPCR with a late endosomal lipid, lysobisphosphatidic acid (LBPA). This exchange requires ALG-2-interacting protein X (ALIX)–dependent endolysosomal sorting. aPL binding specifically to cell surface EPCR-LBPA disrupts an inhibited TF complex and thereby induces coagulation activation that elicits autocrine PAR signaling in monocytes. This initial aPL effect translocates acid sphingomyelinase (ASM) to the cell surface, where it is activated by EPCR-LBPA to alter the procoagulant membrane properties of monocytes. Stereoselective LBPA loading of EPCR is also required for aPL signaling in embryonic trophoblast cells. Procr C/S mice or mice treated with a specific function-blocking antibody to EPCR-LBPA are protected from aPL-induced thrombosis and fetal loss. Notably, EPCR-LBPA engagement not only promotes the detrimental pathological consequences of aPLs but also drives dendritic cell IFN-α production for expansion of aPL-producing B1a cells. In an experimental model of APS, Tlr7−/− and Procr C/S mice cannot expand B1a cells responsible for production of lipid-reactive aPLs. Blockade of EPCR-LBPA signaling is sufficient to prevent the development of aPLs in mice with a TLR7-dependent systemic lupus erythematosus–like syndrome. Moreover, lupus-associated kidney pathology is markedly attenuated by the inhibition of EPCR-LBPA signaling. ### CONCLUSION Pathogenic aPLs recognize a single cell-surface lipid–protein receptor complex that is positioned at the intersections of coagulation and innate immune signaling and involved in the regulation of antimicrobial host defense. Specific blockade of this target not only prevents the pathological consequences of aPLs in vivo but also impairs a self-amplifying autoimmune signaling loop contributing to the development of APS autoimmunity. ![Figure][3] The recognition of EPCR-LBPA by aPLs promotes autoimmunity. The interaction of aPLs with EPCR-LBPA promotes activation of embryonic trophoblast cells, monocytes, and dendritic cells. (Right) On monocytes, disruption of the inhibitory control of the coagulation initiator TF induces cellular activation through PAR signaling, which is responsible for recruiting ASM to the cell surface. EPCR-LBPA activation of ASM then causes procoagulant lipid exposure and aPL endosomal trafficking. The subsequent up-regulation of tumor necrosis factor (TNF) and TF is central to thrombosis and pregnancy complications. (Left) In addition, aPL induction of IFN-α in dendritic cells sustains a TLR7-dependent expansion of aPL-producing B1a cells and thereby promotes autoimmunity. NOX, nicotinamide adenine dinucleotide phosphate oxidase; ROS, reactive oxygen species. Antiphospholipid antibodies (aPLs) cause severe autoimmune disease characterized by vascular pathologies and pregnancy complications. Here, we identify endosomal lysobisphosphatidic acid (LBPA) presented by the CD1d-like endothelial protein C receptor (EPCR) as a pathogenic cell surface antigen recognized by aPLs for induction of thrombosis and endosomal inflammatory signaling. The engagement of aPLs with EPCR-LBPA expressed on innate immune cells sustains interferon- and toll-like receptor 7–dependent B1a cell expansion and autoantibody production. Specific pharmacological interruption of EPCR-LBPA signaling attenuates major aPL-elicited pathologies and the development of autoimmunity in a mouse model of systemic lupus erythematosus. Thus, aPLs recognize a single cell surface lipid–protein receptor complex to perpetuate a self-amplifying autoimmune signaling loop dependent on the cooperation with the innate immune complement and coagulation pathways. [1]: /lookup/doi/10.1126/science.aay1833 [2]: /lookup/doi/10.1126/science.abg6449 [3]: pending:yes

Lipid presentation by the protein C receptor links coagulation with autoimmunity

前十字靭帯急性損傷に対しては早期手術の成績が良好

前十字靭帯 (ACL)損傷は最も一般的なスポーツ外傷の一つで、その頻度は49ー75/100,000人・年とされています。過去には外科的治療と非手術療法を比較した臨床試験（KANON trial）が行われ、運動療法と組み合わせた保存的治療が良好な成績を示すことが示されています(Frobell et al., N Engl J Med 2010;363:331-42; Frobell et al., BMJ 2013;346:f232)。しかしこの結果出てからもACL損傷に対する手術は年々増加しています。これはKANON trialでは少なくとも半数の患者で再建術が不要であったためではないかと考えられています。今回のConservative versus Operative Methods for Patients with ACL Rupture Evaluation (COMPARE) trialでは、ACLの急性損傷に対して早期手術とリハビリテーション後に希望者に待機手術を行った場合との成績を比較しました。

受傷後2カ月以内のACL損傷患者 (18ー65歳)を早期（6週間以内）に再建術を行うEarly reconstruction (E)群、最低3カ月間のリハビリテーション後に不安定性が残存している、あるいは活動レベルに不満がある場合に再建術を行うRehabilitation with optional delayed reconstruction (R)群に振り分けて比較しました。研究に参加した患者は167人で、85人がE群、82人がR群に振り分けられました。E群のうち3名は再建術を受けませんでした（理由は手術に対する恐怖や手術時のpivot shift陰性）。78人はhamstring graft、4人は膝蓋腱 (BTB)を用いて再建されました。R群のうち41人が平均ランダム化後10.6ヵ月で再建術を受けました (38人がhamstring、3人がBTB)。手術は全て関節鏡視下で行われました。

Primary outcomeである術後24ヵ月以降のInternational Knee Documentation Committee scoreを用いた患者の自覚症状、膝機能、スポーツ参加の比較では、E群の方が有意に良好でした（群間差は5.3, 95% confidence interval 0.6 to 9.9）。3カ月後にはR群の方が良好な成績でしたが、点数は９ヵ月後に逆転しました。群間の差は12ヵ月後には小さくなりましたが、その後24ヵ月までE群が良好でした。Secondary outcomeである2年後のKnee Injury and Osteoarthritis Outcome sport score (P=0.039)、quality of life score (P=0.002)いずれもE群で有意に良好な成績を示しました。Lysholm scoreは6, 9, 12, 24ヵ月のfollow-upでいずれもE群で有意に良好でした。安静時および活動時の疼痛に群間差はありませんでした。半月板の処置が必要だったのはE群のうち24例、R群の17例でした。重篤な有害事象としては逆側のACL損傷 (E群で3例、R群で1例)、ACL再断裂 (E群4例、R群2例)。Post hoc analysisでは2年のfollow-up後にgiving wayを訴えた患者はR群で高頻度でした（E群2.5%, R群15.0%）。この研究結果は、ACL急性損傷患者に対しては早期の再建術が良好な成績を示すことを示唆していますが、R群との差は大きなものではなく、臨床的な意義を持つかについては議論の余地があるかもしれません。

Reijman et al., Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial.

BMJ 2021;372:n375

Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial

Objective To assess whether a clinically relevant difference exists in patients’ perceptions of symptoms, knee function, and ability to participate in sports over a period of two years after rupture of the anterior cruciate ligament (ACL) between two commonly used treatment regimens. Design Open labelled, multicentre, parallel randomised controlled trial (COMPARE). Setting Six hospitals in the Netherlands, between May 2011 and April 2016. Participants Patients aged 18 to 65 with an acute rupture of the ACL, recruited from six hospitals. Patients were evaluated at three, six, nine, 12, and 24 months. Interventions 85 patients were randomised to early ACL reconstruction and 82 to rehabilitation followed by optional delayed ACL reconstruction after a three month period (primary non-operative treatment). Main outcomes Patients’ perceptions of symptoms, knee function, and ability to participate in sporting activities were assessed with the International Knee Documentation Committee score (optimum score 100) at each time point over 24 months. Results Between May 2011 and April 2016, 167 patients were enrolled in the study and randomised to one of two treatments (mean age 31.3; 67 (40.%) women), and 163 (98%) completed the trial. In the rehabilitation and optional delayed ACL reconstruction group, 41 (50%) patients underwent reconstruction during follow-up. After 24 months, the early ACL reconstruction group had a significantly better (P=0.026) but not clinically relevant International Knee Documentation Committee score (84.7 v 79.4 (difference between groups 5.3, 95% confidence interval 0.6 to 9.9). After three months of follow-up, the International Knee Documentation Committee score was significantly better (P=0.002) for the rehabilitation and optional delayed ACL reconstruction group (difference between groups −9.3, −14.6 to −4.0). After nine months of follow-up, the difference in the International Knee Documentation Committee score changed in favour of the early ACL reconstruction group. After 12 months, differences between the groups were smaller. In the early ACL reconstruction group, four re-ruptures and three ruptures of the contralateral ACL occurred during follow-up versus two re-ruptures and one rupture of the contralateral ACL in the rehabilitation and optional delayed ACL reconstruction group. Conclusions In patients with acute rupture of the ACL, those who underwent early surgical reconstruction, compared with rehabilitation followed by elective surgical reconstruction, had improved perceptions of symptoms, knee function, and ability to participate in sports at the two year follow-up. This finding was significant (P=0.026) but the clinical importance is unclear. Interpretation of the results of the study should consider that 50% of the patients randomised to the rehabilitation group did not need surgical reconstruction. Trial registration Netherlands Trial Register NL 2618.

Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial

頚椎症性脊髄症に対する前方手術vs後方手術

頚椎症性脊髄症患者（cervical myelopathy, CSM）に対する手術療法において、前方手術が良いか？後方手術が良いか？という議論は神学論争的な趣きもあり、中々決着がつきません。これまでにいくつかの前向き研究は行われており、わが国でも東京医科歯科大学から両者を比較した優れた前向き試験が報告されていますし (Hirai et al., Spine. 2011;36(23):1940-7; Hirai et al., J Orthop Sci. 2018;23(1):32-38)、海外からも本論文の著者らの報告を含めていくつかの研究が発表されています (Ghogawala et al., Neurosurgery. 2011;68(3):622-630; King et al., Neurosurgery. 2009;65(6):1011-1022)。これまでの結果では前方手術のほうが良好とするものが多いようですが、ランダム化比較試験は行われていませんでした。

本研究はアメリカの14施設、カナダの1施設において、MRIあるいはミエロCTで確認された45歳～80歳のCSM患者をブロックランダム化によって前方手術群および後方手術群に振り分けました。C2-C7 kyphosis＞5度、segmental hyphotic deformity、高度なOPLL、過去の頚椎手術歴、ASA class IV以上の患者は除外されています。前方手術は除圧・植骨およびプレートによる固定、後方手術については北米ではlaminoplastyに慣れていない脊椎外科医が多いということで、laminoplastyの技術がある8人の外科医は後方手術に振り分けられた患者は後方除圧固定術あるいはlaminoplasty（片開き式？）を自由に選ぶということになっています。Primary outcomeは1年後のSF-36のphysical component summary（PCS）の変化、secondary outcomeとしてはmodified JOA score, neck disability indexそしてEQ-5Dを用いたQALYs、休職期間等となっています。

458人の患者がスクリーニングされ、結果的に163人がランダム化されました。前方固定が66例、後方手術が97名（laminoplasty 28名、固定術69名）でした。術前の背景因子に有意差は有りませんでした。

結果は下記のとおりです。

①Primary outcomeである1年後のSF-36 PCSは前方手術群と後方手術群で有意差は有りませんでした (5.9 vs 6.2; P=0.86)。また2年後の変化も5.2 vs 6.0 (P=0.46)と有意差なしでした。Secondary outcomesの大半（6/7）で有意差なしでした。

②合併症は前方手術で有意に多いという結果でした (47.6% vs 24.0%; P=0.002)。主なものとしては嚥下障害 (41% vs 0%)、神経学的障害 (2% vs 9%)、再手術 (6% vs 4%)、30日以内の再入院 (0% vs 7%)などで、major complicationについては両者で差がありませんでした (22.2% vs 17.0%)。

③ランダム化されていない各術式間の比較では、laminoplastyのSF-36 PCS改善が有意に良好でした (laminoplasty, 後方固定、前方固定それぞれで1年後9.6, 4.6, 5.7　2年後10.1, 4.3, 5.0)。また術後合併症についてもlamnoplastyが有意に少ないという結果でした。

ということでこのRCTでは前方、後方手術の術後成績には差がないという結果でしたが、非ランダム化比較の結果およびlaminoplastyに慣れていない術者が多いということを考慮するとlaminoplastyに軍配が上がるような気がします。後方手術がメインである日本としては何となくうれしい結果です。後方手術を紹介する文献が獨協医科大学脳神経外科の金先生の論文なのは、本論文の著者がneurosurgeonだからでしょうか。。

Zoher Ghogawala et al.

Effect of Ventral vs Dorsal Spinal Surgery on Patient-Reported Physical Functioning in Patients With Cervical Spondylotic Myelopathy: A Randomized Clinical Trial. JAMA. 2021 Mar 9;325(10):942-951. doi: 10.1001/jama.2021.1233.

https://jamanetwork.com/journals/jama/fullarticle/2777236

腹腔内のGATA6陽性マクロファージが組織修復および癒着に関与する

体腔coelomic cavityが存在する無脊椎動物（例えばウニなどの後生動物metazoansなど）では、体腔の損傷が生じると食作用を有する免疫細胞である体腔細胞coelomocytesが速やかに損傷部位に集積して損傷修復を行うことが知られています。このような細胞集積は極めて速やかに生じ、哺乳類における血小板凝集による止血反応に類似した過程です。

哺乳類にも腹腔や胸腔、心嚢などの体腔が存在しますが、その損傷もやはり速やかに修復されます。一方腹腔内の手術後には約66%の患者で無菌的な癒着が生じ、これがイレウスの原因になるなど、様々な問題を起こすことが知られています。この論文で著者らは腹腔内のGATA6陽性マクロファージ (GATA6+Mφ)が、腹膜損傷の修復に関与するとともに術後の癒着にも関与することを明らかにしました。

マウス腹膜にレーザーで熱傷を起こすと、腹腔内の損傷部位にGATA6+Mφが接着・集積して細胞塊aggregatesを形成することで損傷修復を行います。この反応は15分程度で完成する極めて速やかな過程であり、血小板の凝集に匹敵するものです。GATA6+Mφの凝集過程は様々な点で血小板凝集に類似していますが、後者が血管内で生じるのに対し、前者は血管外で生じるという空間的な違いがありました。

このような腹腔修復に関与するGATA6+Mφは、腹壁に存在するGATA陰性Mφとは異なって正常状態では腹腔液中に浮遊状態で存在しますが、腹膜の損傷によってfluid shear stressを介して損傷部位へ接着・凝集します。In vitro細胞培養においてもGATA6+Mφは細胞塊を形成し、この過程は2価カチオンのキレート剤EDTAで抑制され、ATP添加で促進されました。

著者らはこのGATA6+Mφの凝集に関与する分子を検討しました。GATA6+Mφの凝集はインテグリンやセレクチン、そしてICAMなどのimmunoglobulin-like adhesion moleculesなど様々な接着分子をブロックしても変化しませんでしたが、ヘパリンによって抑制されました。海綿動物の体腔細胞において、scavenger receptor cystein-rich (SRCR) domainを有するSRCR superfamily proteinsが接着分子として働くことにヒントを得て、マウスのGATA+マクロファージの接着においてもSRCR family分子が関与する可能性を検討し、MARCO (macrophage receptor with collagenous structure)およびMSR1 (macrophage scavenger receptor)という２つのclass A scavenger receptorsのブロックによってGATA6+Mφの凝集が強力に抑制されることが明らかになりました。

最後に同様の現象が無菌的な腹腔内癒着にも関与する可能性を、マウス腹腔内癒着モデルを用いて検証し、3時間で癒着部位に多数のMφが集積し、この過程はscavenger receptorsのブロックによって抑制されることを示しました。

この研究は腹腔内GATA6+Mφが血小板と類似した動態を示して組織修復に働くこと、この過程にSRCR family分子が関与すること、またこの修復過程が無菌的癒着にも関与することをin vivo imagingを利用して見事に示したという点で非常に重要なものです。術後癒着は外科領域における大きな課題であり、SRCR family分子の抑制がその解決に寄与する可能性を示しています。

余談ですが、この論文を読んで、ずっと前に読んだscavenger receptorがMφの接着に重要であることを示した論文を思い出しました (Fraser I et al., Nature. 1993 Jul 22;364(6435):343-6)。しかしこの論文ではMφの接着はdivalent cation-independentとなっているのですが、この違いはどのような機序なのでしょう？

J. Zindel et al., Primordial GATA6 macrophages function as extravascular platelets in sterile injury. Science  05 Mar 2021: Vol. 371, Issue 6533, eabe0595 DOI: 10.1126/science.abe0595

Primordial GATA6 macrophages function as extravascular platelets in sterile injury

GATA6+ macrophages resident in body cavities exhibit both phagocytic and repair functions. However, the mechanisms by which these cells can identify and migrate to sites of injury have remained unclear. Using intravital imaging of mouse peritoneal cavities, Zindel et al. report that GATA6+ macrophages rapidly assemble clot-like structures in a process strongly analogous to thrombosis (see the Perspective by Herrick and Allen). The formation of these aggregates requires the expression of macrophage scavenger receptor domains and acts to plug wounds and promote healing. This pathway can be inadvertently activated during medical procedures, when macrophage aggregates can promote the generation of abdominal scar tissue known as adhesions. Inhibition of macrophage scavenger receptors may therefore be a useful therapeutic approach after surgeries that cause injury to body cavities. Science , this issue p. [eabe0595][1]; see also p. [993][2] ### INTRODUCTION Most multicellular organisms have a major body cavity that harbors immune cells. In primordial species such as the purple sea urchin, these cells—called coelomocytes—fulfill dual functions. Sea urchin coelomocytes clear pathogens from the peritoneal compartment, but they have also been shown to form multicellular aggregates that adhere to injured tissue and are crucial for repair. In mammals, the peritoneal, pleural, and pericardial cavities are filled with vast numbers of resident GATA6+ cavity macrophages. The role of peritoneal cavity macrophages as phagocytes in clearing pathogens has been established for decades. Recent evidence suggests that these cells migrate to injuries within the peritoneal cavity, where they have been shown to promote tissue repair. ### RATIONALE It remains unclear how cavity macrophages, which are suspended in the fluid phase (peritoneal fluid), can identify injuries, which can be several thousand micrometers away, and how they can exhibit chemotaxis over that distance through a fluid-filled compartment that is under constant convective flow. In this study, we developed an intravital microscopy (IVM) model to study the dynamics and molecular mechanisms of resident GATA6+ macrophage recruitment in the peritoneal cavity after injury. ### RESULTS By using inverted multiphoton IVM with extremely sensitive non-descanned hybrid detectors, we were able to image the peritoneal cavity through the intact abdominal wall in living animals. The tracks of the rapidly moving peritoneal macrophages showed that they passively traversed the peritoneal cavity in a respiration-dependent and seemingly random pattern. Next, we used a focused high-power infrared laser beam to induce focal injuries to the peritoneum, and we imaged the subsequent immune response. We found that peritoneal macrophages were rapidly recruited through a two-step process: (i) an initial tether of macrophages to the injury site, followed by (ii) secondary tethers that formed an aggregate reminiscent of a thrombus-like structure in response to injury. Macrophage aggregation mirrored and rivaled the speed of platelet aggregation (thrombus formation) in the adjacent vasculature. By probing the transcriptome of peritoneal macrophages and a targeted series of knockout and inhibition IVM experiments, we found that peritoneal macrophage aggregation was independent of canonical mammalian adhesion molecules such as integrins, selectins, and immunoglobulin-like adhesion molecules. Instead, peritoneal macrophage aggregation was dependent on primordial scavenger receptor cysteine-rich (SRCR) domains. SRCR domains are highly conserved among species, with many homologs expressed by sea urchin coelomocytes and sea sponges, and some of these proteins have been identified as cell-cell adhesion molecules in these primordial organisms. Aggregates of cavity macrophages physically sealed injuries and promoted rapid repair of focal peritoneal lesions. However, in abdominal surgery models that reflect iatrogenic surgical situations in which the peritoneal cavity is opened and foreign suture material is introduced, these cavity macrophages formed extensive aggregates that promoted the growth of intra-abdominal scar tissue called peritoneal adhesions. These peritoneal adhesions cause substantial morbidity for patients and considerable costs for health care systems. We showed that the number and tenacity of peritoneal adhesions was significantly reduced by either depleting peritoneal macrophages or therapeutically inhibiting their scavenger receptor–dependent recruitment and aggregation. ### CONCLUSION Our results unveil a platelet-like extravascular fluid-phase response by macrophages. This rapid response seals the peritoneal leaks within minutes and serves an important function in repairing small injuries such as focal thermal or laser-induced peritoneal injuries. We hypothesize that such focal injuries reflect a type of injury for which the immune system has evolved a beneficial response. By contrast, iatrogenic procedures, such as abdominal surgery involving implantation of foreign material, reflect a type of injury that has no evolutionary precedent. In this scenario, peritoneal macrophages may cause detrimental scarring, instead of restitution ad integrum, in an attempt to repair the wound. Thus, macrophage aggregation and its inhibition by scavenger receptor antagonists are of clinical importance and may provide a therapeutic target to prevent scar formation after surgery in the peritoneal cavity. Furthermore, these findings may extend to other cavities, including pleural and pericardial spaces. ![Figure][3] Aggregation of GATA6+ peritoneal cavity macrophages in response to laser-induced peritoneal injury. ( A ) Human, mouse, and sea urchin coelomic cavities (mouse example enlarged) with circulating coelomocytes and macrophages. Injuries were induced by a multiphoton laser. ( B ) IVM image immediately after injury. Scale bar, 50 μm. ( C ) IVM image 30 min after injury. Scale bar, 50 μm. ( D ) Aggregation was dependent on scavenger receptors and a (yet unknown) polyanionic ligand. Most multicellular organisms have a major body cavity that harbors immune cells. In primordial species such as purple sea urchins, these cells perform phagocytic functions but are also crucial in repairing injuries. In mammals, the peritoneal cavity contains large numbers of resident GATA6+ macrophages, which may function similarly. However, it is unclear how cavity macrophages suspended in the fluid phase (peritoneal fluid) identify and migrate toward injuries. In this study, we used intravital microscopy to show that cavity macrophages in fluid rapidly form thrombus-like structures in response to injury by means of primordial scavenger receptor cysteine-rich domains. Aggregates of cavity macrophages physically sealed injuries and promoted rapid repair of focal lesions. In iatrogenic surgical situations, these cavity macrophages formed extensive aggregates that promoted the growth of intra-abdominal scar tissue known as peritoneal adhesions. [1]: /lookup/doi/10.1126/science.abe0595 [2]: /lookup/doi/10.1126/science.abg5416 [3]: pending:yes

Primordial GATA6 macrophages function as extravascular platelets in sterile injury

TNF-αは静脈内皮細胞におけるClaudin-11低下を介して静脈からのChloride漏出を誘導する

この論文で著者らはTNF-αが静脈特異的にChlorideイオンの漏出を促進し、その過程にはTNF-αによる静脈内皮細胞の細胞間tight junctionタンパクClaudin-11の低下が関与していることを明らかにしました。TNF-αの下流ではPanx1 channel活性化→TRPV4 Ca++ channelの活性化が生じ、これがATPの細胞外への放出を誘導します。放出されたATPはendonucleotidease CD39によってadenosineへと加水分解を受け、A2A adenosine受容体の活性化を誘導し、結果として静脈内皮細胞におけるClaudin-11の低下と漏出増加をきたします。著者らはこれが敗血症におけるTNF-αの病態形成メカニズムの一つではないかとしています。

関節リウマチの病態においてもTNF-αによる静脈からのChloride漏出が関与しているのでしょうか？ところでMTXは細胞外adenosineを増加させ、A2A 受容体を活性化することが抗炎症作用に働く可能性が報告されています。A2A 受容体活性化という点ではMTXとTNF-αと共通しているようにも思えるのですが、両者の作用がどのような関係にあるのかは興味深いところです。

Maier-Begandt D et al., A venous-specific purinergic signaling cascade initiated by Pannexin 1 regulates TNFα-induced increases in endothelial permeability. Sci Signal. 2021 Mar 2; 14(672): eaba2940.

A venous-specific purinergic signaling cascade initiated by Pannexin 1 regulates TNFα-induced increases in endothelial permeability

A challenge in treating sepsis, a potentially life-threatening, systemic inflammatory disorder, is the increase in endothelial permeability that leads to widespread tissue edema and immune cell infiltration. Maier-Begandt et al. uncovered a signaling pathway activated specifically in veins by TNFα, a proinflammatory cytokine whose circulating concentrations increase greatly during sepsis. TNFα treatment resulted in the activation of Panx1 channels, which stimulated a signaling pathway that led to disrupted tight junctions in veins but not in arteries. Sepsis induced less lung edema and was less fatal to Panx1-deficient mice compared to control mice. Thus, targeting this pathway may improve survival in patients experiencing sepsis. The endothelial cell barrier regulates the passage of fluid between the bloodstream and underlying tissues, and barrier function impairment exacerbates the severity of inflammatory insults. To understand how inflammation alters vessel permeability, we studied the effects of the proinflammatory cytokine TNFα on transendothelial permeability and electrophysiology in ex vivo murine veins and arteries. We found that TNFα specifically decreased the barrier function of venous endothelium without affecting that of arterial endothelium. On the basis of RNA expression profiling and protein analysis, we found that claudin-11 (CLDN11) was the predominant claudin in venous endothelial cells and that there was little, if any, CLDN11 in arterial endothelial cells. Consistent with a difference in claudin composition, TNFα increased the permselectivity of Cl− over Na+ in venous but not arterial endothelium. The vein-specific effects of TNFα also required the activation of Pannexin 1 (Panx1) channels and the CD39-mediated hydrolysis of ATP to adenosine, which subsequently stimulated A2A adenosine receptors. Moreover, the increase in vein permeability required the activation of the Ca2+ channel TRPV4 downstream of Panx1 activation. Panx1-deficient mice resisted the pathologic effects of sepsis induced by cecal ligation and puncture on life span and lung vascular permeability. These data provide a targetable pathway with the potential to promote vein barrier function and prevent the deleterious effects of vascular leak in response to inflammation.

A venous-specific purinergic signaling cascade initiated by Pannexin 1 regulates TNFα-induced increases in endothelial permeability