Investigation for the possibility of CaMKII activity modulation for the therapeutic optical in rheumatoid arthritis

在类风湿性关节炎(RA)中，显著的增殖和抗凋亡作用是至关重要的。其中，我们重点关注了PI3K/Akt通路的重要性，并在最近两年中试图研究CaMKII通路的作用。培养的FLS表达CaMKIIγ和δ，尤其是δ亚型。加入CaMKII化学抑制剂KN93可显著增强FLS对TRAIL和抗Fas抗体的凋亡敏感性。另外的实验表明，CaMKII诱导的细胞凋亡敏感性现象是通过Akt介导的。CaMKII是一种被钙离子内流激活的酶。钙离子内流也激活了PADI，PADI是多肽瓜氨酸化转录后机制的关键酶。多肽瓜氨酸化的转录后机制被认为是RA患者产生抗CCP抗体的关键，而CCP抗体是一种RA特异性自身抗体。然而，在培养的FLS中，我们没有检测到对钙离子内流、促炎细胞因子或促凋亡刺激的反应的瓜氨酸肽。因此，我们利用人类细胞株HL-60进行了实验。HL-60细胞表达CaMKIIγ亚型。在全反式维甲酸诱导HL-60向粒系分化的过程中，PADI4、瓜氨酸多肽和Akt磷酸化均有明显的表达。考虑到CaMKII和Akt之间可能的串扰，CaMKII、Akt和多肽瓜氨酸化过程之间似乎存在另一种串扰。这些机制被认为是类风湿关节炎重要的研究课题，加强了CaMKII在类风湿关节炎中的靶分子作用。

The remarkable proliferation as well as apoptosis resistance are crucial for rheumatoid arthritis (RA). Among them, we have focused on the importance of PI3K/Akt pathway, and in the current 2 years, we have tried to investigate the role of CaMKII pathway. FLS in culture expressed CaMKII γ and δ, especially δ isoform. The addition of CaMKII chemical inhibitor, KN93, significantly augmented apoptosis sensitivity of FLS in response to TRAIL and anti-Fas antibody. The additional experiment showed that CaMKII-induced phenomena of apoptosis sensitivity are mediated through Akt. CaMKII is an enzyme that is activated by Ca ion influx. Ca ion influx also activates PADI, which is an essential enzyme for post-transcriptional mechanism of peptide citrullination. Post-transcriptional mechanism of peptide citrullination is thought to be crucial for anti-CCP antibodies production in patients with RA, a RA-specific autoantibodies. However, we could not detect the citrullinated peptides in cultured FLS in response to Ca ion influx, pro-inflammatory cytoltines or pro-apoptotic stimuli. Thus, we conducted the experiment by the use of human cell line, HL-60. HL-60 expressed CaMKII γ isoform. A significant expression of PADI4, citrullinated peptides and Akt phosphorylation was found during the course of granulocyte-lineage differentiation of HL-60 by ATRA According to the results obtained in the current 2 years, an association between CaMKII and FLS apoptosis is demonstrated. Considering a possible cross-talk between CaMKII and Akt, another cross-talk among CaMKII, Akt and the peptide citrullination process appears to be present. These mechanisms are thought to be important research issue of RA that strengthens a role of CaMKII for a target molecule in RA.