α8β1 integrin regulates nutrient absorption through an Mfge8-PTEN dependent mechanism.

Coordinated gastrointestinal smooth muscle contraction is critical for proper nutrient absorption and is altered in a number of medical disorders. In this work, we demonstrate a critical role for the RGD-binding integrin α8β1 in promoting nutrient absorption through regulation of gastrointestinal motility. Smooth muscle-specific deletion and antibody blockade of α8 in mice result in enhanced gastric antral smooth muscle contraction, more rapid gastric emptying, and more rapid transit of food through the small intestine leading to malabsorption of dietary fats and carbohydrates as well as protection from weight gain in a diet-induced model of obesity. Mechanistically, ligation of α8β1 by the milk protein Mfge8 reduces antral smooth muscle contractile force by preventing RhoA activation through a PTEN-dependent mechanism. Collectively, our results identify a role for α8β1 in regulating gastrointestinal motility and identify α8 as a potential target for disorders characterized by hypo- or hyper-motility

Experimental Studies on Antitumor Activity of Rabbit Alveolar Macrophages during Carcinogenesis

肺胞マクロファージは,常に外気と接触し刺激を受けている細胞であり肺胞内細胞の90%以上を占め,生体防御機構において重要な働きをしているものと考えられている。また肺内における環境の変化に対応して腫揚免疫においても重要なエフェクター細胞と考えられる。しかし,肺癌の発癌過程における肺胞マクロファージの免疫学的意義は,十分に明らかではない。そこで著者は家兎を用い,肺胞マクロファージの機能的変化を,抗腫瘍活性を中心に検討した。 まず,家兎の肺胞マクロファージは,気管支ファイバースコープにてBALを行う事により採取したが,はじめにその方法,間隔について検討した。次に家兎の肺に化学発癌を惹起させ,発癌過程における肺胞マクロファージの機能的変化を観察した。さらにBRMを用いその抗腫瘍活性の増強方法について検討し,以下の結論を得た。 1) 家兎における,気管支ファイバースコープを用いたBALは,注入量20ml,洗浄回数2回で2～3×10個の肺胞マクロファージを回収できた。 2) BALの施行間隔を1週間以下とした場合,肺胞内細胞成分または肺胞マクロファージの機能に変化が認められた。2週間では変化を認めなかった。 3) 家兎肺胞マクロファージは,6種のヒト培養腫瘍細胞株に対し,増殖抑制能を示したが,正常細胞であるヒト線維芽細胞に対しては,増殖抑制能を示さなかった。 4) MNUを左主気管支に注入し, 12週で1羽/3羽, 24週で3羽/3羽の中枢型肺癌の発生を認めた。 5) その発癌過程における肺胞マクロファージの腫瘍細胞増殖抑制能を観察し,経時的な上昇を認めた。 6) 実験12週で屠殺した2羽の家兎において,発癌家兎と非発癌家兎の間で腫瘍細胞増殖抑制能の上昇の程度には差を認めなかった。実験24週で屠殺した3羽の家兎において癌腫の浸潤の程度と腫瘍細胞増殖抑制能の上昇に関連は認められなかった。 7) 発癌過程における肺胞マクロファージのNBT還元能は有意な変化を示さず,貪食能は経時的な低下,免疫抑制活性は経時的な上昇を認めた。免疫抑制活性は個体差を認めた。 8) 発癌過程における肺胞マクロファージの腫癌細胞増殖抑制能は,免疫抑制活性との間に正の相関を認め,貪食能との問には負の相関を認めた。 9) LPS, N-CWS, IFNγは,腫瘍細胞に対し,直接の増殖抑制作用は示さず, TNFは腫蕩細胞に対し,腫瘍細胞の種頬によっては直接,増殖抑制作用を示した。 10) LPS, N-CWS, IFNγは,それぞれ肺胞マクロファージの腫瘍細胞増殖抑制能を増強させた。 11) その場合IFNγに対する反応性は,個体差が認められ反応性を示さないものも認められた。 12) 反応性を示さない家兎においてもIFNγ添加後にLPSを添加した場合は, IFNyに容量依存性作用の発現を認めた。 13) 併用の場合他に, N-CWSとIFNγ, N-CWSとTNFおよびIFNyとTNFの組み合わせにおいて肺胞マクロファージの腫瘍細胞増殖抑制能増強作用に関して相乗効果が認められた。TNFを含む組み合わせでは,特にTNF resistant cell lineに対して強い相乗効果を認めた。 以上より肺胞マクロファージは発癌の初期段階において抗腫瘍性を上昇させており,それはBRMの併用により効果的に上昇させ得ることが試験管内において確認できた。但し腫瘍細胞増殖抑制能と免疫抑制活性の間には相関が認められ肺胞マクロファージの抗腫癌性の検討の際に注意が必要であると思われた。To examine the effects of carcinogenesis on the antitumor activity of alveolar macrophages, MNU was instilled into the rabbit bronchus to produce cancer, and changes in rabbits were observed for the next 24 weeks. Alveolar samples were collected by bronchofiberscopic BAL (Bronchoalveolar lavage), which does not require animal sacrifice. Although BAL itself causes changes in the lung, it was confirmed an interval of two weeks allows BAL to be performed serially. Significant changes with time in the total cell count and differential cell count in BALF (Bronchoalveolar lavage fluid) were not seen. Functions of PAM were as follows: cytostatic activity increased progressively, phagocytosis gradually decreased, and both showed significant differences from pre-values. No significant change with time was noted m the NBT reduction. Suppressor activity increased with time in some rabbits, and showed a significant correlation with cytostatic activity. The in vitro effect of BRMs on the cytostatic activity of alveolar macrophage was also studied. LPS potenbated the cytostatic activity against each of 3 kinds of target cells, while N-CWS, IFN and TNF each potentiated activity partially. When these were used in combinations, synergistic effects were observed between LPS and IFN, between N-CWS and IFN and between TNF and N-CWS.広島大学医学雑誌, 37(3), 347-389, 平1-6月 (1989)広島大学(Hiroshima University)博士(医学)Medicinedoctora

New Therapeutic Targets for Hepatic Fibrosis in the Integrin Family, α8β1 and α11β1, Induced Specifically on Activated Stellate Cells

A huge effort has been devoted to developing drugs targeting integrins over 30 years, because of the primary roles of integrins in the cell-matrix milieu. Five αv-containing integrins, in the 24 family members, have been a central target of fibrosis. Currently, a small molecule against αvβ1 is undergoing a clinical trial for NASH-associated fibrosis as a rare agent aiming at fibrogenesis. Latent TGFβ activation, a distinct talent of αv-integrins, has been intriguing as a therapeutic target. None of the αv-integrin inhibitors, however, has been in the clinical market. αv-integrins commonly recognize an Arg-Gly-Asp (RGD) sequence, and thus the pharmacophore of inhibitors for the 5-integrins is based on the same RGD structure. The RGD preference of the integrins, at the same time, dilutes ligand specificity, as the 5-integrins share ligands containing RGD sequence such as fibronectin. With the inherent little specificity in both drugs and targets, “disease specificity” has become less important for the inhibitors than blocking as many αv-integrins. In fact, an almighty inhibitor for αv-integrins, pan-αv, was in a clinical trial. On the contrary, approved integrin inhibitors are all specific to target integrins, which are expressed in a cell-type specific manner: αIIbβ3 on platelets, α4β1, α4β7 and αLβ2 on leukocytes. Herein, “disease specific” integrins would serve as attractive targets. α8β1 and α11β1 are selectively expressed in hepatic stellate cells (HSCs) and distinctively induced upon culture activation. The exceptional specificity to activated HSCs reflects a rather “pathology specific” nature of these new integrins. The monoclonal antibodies against α8β1 and α11β1 in preclinical examinations may illuminate the road to the first medical agents

New Therapeutic Targets for Hepatic Fibrosis in the Integrin Family, α8β1 and α11β1, Induced Specifically on Activated Stellate Cells

A huge effort has been devoted to developing drugs targeting integrins over 30 years, because of the primary roles of integrins in the cell-matrix milieu. Five αv-containing integrins, in the 24 family members, have been a central target of fibrosis. Currently, a small molecule against αvβ1 is undergoing a clinical trial for NASH-associated fibrosis as a rare agent aiming at fibrogenesis. Latent TGFβ activation, a distinct talent of αv-integrins, has been intriguing as a therapeutic target. None of the αv-integrin inhibitors, however, has been in the clinical market. αv-integrins commonly recognize an Arg-Gly-Asp (RGD) sequence, and thus the pharmacophore of inhibitors for the 5-integrins is based on the same RGD structure. The RGD preference of the integrins, at the same time, dilutes ligand specificity, as the 5-integrins share ligands containing RGD sequence such as fibronectin. With the inherent little specificity in both drugs and targets, “disease specificity” has become less important for the inhibitors than blocking as many αv-integrins. In fact, an almighty inhibitor for αv-integrins, pan-αv, was in a clinical trial. On the contrary, approved integrin inhibitors are all specific to target integrins, which are expressed in a cell-type specific manner: αIIbβ3 on platelets, α4β1, α4β7 and αLβ2 on leukocytes. Herein, “disease specific” integrins would serve as attractive targets. α8β1 and α11β1 are selectively expressed in hepatic stellate cells (HSCs) and distinctively induced upon culture activation. The exceptional specificity to activated HSCs reflects a rather “pathology specific” nature of these new integrins. The monoclonal antibodies against α8β1 and α11β1 in preclinical examinations may illuminate the road to the first medical agents

Enhanced biological activity of polymeric osteopontin

Osteopontin is a multifunctional glycoprotein with roles in immunomodulation, inflammatory response, tissue mineralization, and tissue remodeling, which are mediated primarily through integrins. Transglutaminase 2 selectively cross-links proteins by isopeptide bonding. Osteopontin is one of the substrates of this enzyme and undergoes polymerization; however, the biological meaning of this polymerization remains unknown. Using recombinant osteopontin polymerized with purified transglutaminase 2, we examined cell adhesion, spreading, focal contact formation, and migration of SW480 or HUVE cells. All of these cellular behaviors were dramatically enhanced with polymeric osteopontin. These enhancements of cellular functions imply that polymerization might modulate physiological and pathological functions of osteopontin