Randi Magnus Sommerfelt

• Sommerfelt, Randi Magnus; Feuerherm, Astrid Jullumstrø; Skuland, Trine & Johansen, Berit (2015). Cytosolic phospholipase A2 modulates TLR2 signaling in synoviocytes. PLOS ONE. 10(4). doi: 10.1371/journal.pone.0119088. Fulltekst i vitenarkiv Vis sammendrag

  Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovitis leading to destruction of cartilage and bone. PLA2 enzymes are key players in inflammation regulating the release of unsaturated fatty acids such as arachidonic acid (AA), a precursor of pro-inflammatory eicosanoids. Several lines of evidence point to toll-like receptors (TLRs) as drivers of synovitis and joint destruction in RA. However, few studies have addressed the implication of PLA2 activity downstream TLR activation in the synovium. Here, we aimed to characterize PLA2 enzyme involvement in TLR2-induced signaling in synovial fibroblast-like cells. TLRs1-7 and a range of sPLA2, iPLA2 and cPLA2 enzymes were found to be transcriptionally expressed in cultured synoviocytes. Activation of TLR2/1 and TLR2/6 led to phosphorylation of cPLA2α at Ser505, and induced AA release and PGE2 production; effects that were attenuated by cPLA2α inhibitors. In contrast, sPLA2 inhibitors did not affect AA or PGE2 release. cPLA2α inhibitors furthermore attenuated TLR-induced expression of IL-6, IL-8 and COX2. COX1/2 inhibitors attenuated TLR2/6-induced IL-6 transcription and protein production comparable to cPLA2α inhibition. Moreover, exogenously PGE2 added alone induced IL-6 production and completely rescued IL-6 transcription when added simultaneously with FSL-1 in the presence of a cPLA2α inhibitor. Our results demonstrate for the first time that cPLA2α is involved in TLR2/1- and TLR2/6-induced AA release, PGE2 production and pro-inflammatory cytokine expression in synoviocytes, possibly through COX/PGE2-dependent pathways. These findings expand our understanding of cPLA2α as a modulator of inflammatory molecular mechanisms in chronic diseases such as RA.

• Feuerherm, Astrid Jullumstrø; Jørgensen, Katarina Mariann; Sommerfelt, Randi Magnus; Eidem, Live Egeland; Lægreid, Astrid & Johansen, Berit (2013). Platelet-activating factor induces proliferation in differentiated keratinocytes. Molecular and Cellular Biochemistry. ISSN 0300-8177. 384(1-2), s. 83–94. doi: 10.1007/s11010-013-1784-6. Fulltekst i vitenarkiv
• Sommerfelt, Randi Magnus; Feuerherm, Astrid Jullumstrø; Jones, Kymry & Johansen, Berit (2013). Cytosolic phospholipase A2 regulates TNF-induced production of joint destructive effectors in synoviocytes. PLOS ONE. 8(12). doi: 10.1371/journal.pone.0083555. Fulltekst i vitenarkiv Vis sammendrag

  Introduction: Rheumatoid arthritis (RA) is an inflammatory disease of the joint characterized by chronic synovitis causing pain, swelling and loss of function due to destruction of cartilage and bone. The complex series of pathological events occurring in RA is largely regulated via excessive production of pro-inflammatory cytokines, the most prominent being tumor necrosis factor (TNF). The objective of this work was to elucidate possible involvement of group IVA cytosolic phospholipase A2 (cPLA2α) in TNF-induced regulation of synovitis and joint destructive effectors in RA, to evaluate the potential of cPLA2α as a future therapeutic target. Methods: The involvement of cPLA2α in tumor necrosis factor (TNF)-induced intracellular signaling cascades in synoviocytes (synovial fibroblast-like cells) was analyzed by arachidonic acid (AA) release assay, synoviocyte enzyme activity assay, gene expression analysis by real-time PCR and ELISA immunoassay for the detection of prostaglandin E2 (PGE2), interleukin 8 (IL8) and stromelysin-1 (MMP3), respectively. Results: Inhibitors of cPLA2α enzyme activity (AVX002, ATK) significantly reduced TNF-induced cellular release of AA, PGE2, IL8 and MMP3. This reduction was evident both at transcriptional, protein or metabolite levels. Interestingly, cPLA2α inhibition affected several key points of the arachidonyl cascade; AA-release, cyclooxygenase-2 (COX2) expression and PGE2 production. Furthermore, the results suggest that cPLA2α is subject to transcriptional auto-regulation as inhibition of cPLA2α resulted in reduced PLA2G4A gene expression in TNF-stimulated synoviocytes. Conclusions: cPLA2α appears to be an important regulator of central effectors of inflammation and joint destruction, namely MMP3, IL8, COX2, and PGE2. Decreased transcription of the PLA2G4A and COX2 genes in response to cPLA2α enzyme inhibition further suggest a self-reinforcing effect of cPLA2α inhibition in response to TNF. Collectively, these results support that cPLA2α is an attractive therapeutic target candidate as its inhibition reduces the production of multiple key pro-inflammatory factors involved in RA pathogenesis.

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• Sommerfelt, Randi Magnus; Feuerherm, Astrid Jullumstrø; Jones, Kymry; Tunset, Hanna Maja & Johansen, Berit (2013). cPLA2α REGULATES TNF-INDUCED EFFECTORS OF SYNOVITIS AND JOINT DESTRUCTION IN FIBROBLAST-LIKE SYNOVIOCYTES. Fulltekst i vitenarkiv
• Sommerfelt, Randi Magnus; Feuerherm, Astrid Jullumstrø & Johansen, Berit (2014). Molecular mechanisms of inflammation - a central role for Phospholipase A2. NTNU, Institutt for Biologi. Fulltekst i vitenarkiv
• Johansen, Anide; Feuerherm, Astrid Jullumstrø & Sommerfelt, Randi Magnus (2014). Characterization of Cellular Effects of Insulin in SW982 Fibroblast-like Synoviocytes. Norges teknisk-naturvitenskapelige universitet. Fulltekst i vitenarkiv Vis sammendrag

  A Western diet is characterized by several components, but the main traits are a substantial consumption of red meats, refined carbohydrates and saturated fatty acids. Poor dietary choices and a low level of physical activity can quickly lead to lifestyle diseases like obesity and metabolic syndrome. It has previously been shown that the macronutrient composition of the diet affects the low-grade systemic inflammation in obese men. Both metabolic syndrome and obesity is linked to hyperinsulinemia and insulin resistance. Insulin signals through the insulin receptor (IR), which subsequently leads to many cellular responses including the activation of nuclear factor-κB (NF- κB) and induction of pro-inflammatory mediator production. Increasing body mass index has been linked to increasing disease activity scores (DAS28) for Rheumatoid Arthritis (RA) patients. RA is an autoimmune disease of the synovial membrane of joints, which becomes a hyperplastic, invasive tissue teeming with immunocompetent cells. This will eventually lead to excessive bone loss and chronic inflammation of the synovial membrane, a condition called synovitis. The effect of chronic elevated levels of insulin on disease activity of RA is not yet known. Here, we investigate the potential of insulin to activate cytosolic phospholipase A2α (cPLA2α), which has been shown to be a key regulator of inflammation in RA, in a cell model for synovitis (SW982). In this master s thesis we also investigate a potential role for insulin in regulating proliferation and gene expression in SW982. More specifically, the time-dependent regulation of the genes insulin receptor (IR), insulin-like growth factor 1 receptor (IGF1R), c-Myc, c-Fos and interleukin 6 (IL-6) was investigated. Detection of IR and IGF1R expression by real time quantitative polymerase chain reaction (RT-qPCR) in SW982 synoviocytes, validated for the first time that these cells express the respective receptors and that they are potentially susceptible to insulin signaling.The activity of cPLA2α in response to insulin was evaluated using a radioactive release assay in pre-labeled SW982 cells, which measures the activity of cPLA2α by measuring the amount of arachidonic acid (AA) released from the cells. These tests showed that insulin did not increase the release of AA. However, this test did reveal a trend of decreased release of oleic acid (OA) in response to insulin. These results suggest a PLA2 independent pathway for insulin signaling. Also, a pro-inflammatory role of insulin mediated through the hormone sensitive lipase (HSL) is speculated upon based on these results.MTT viability assay was used to evaluate the effect of insulin on the metabolic activity of cultured SW982s. We found that insulin increases the metabolic activity by ~50% in a time, confluency and dose dependent manner. However, these results were not validated as increased proliferation by flow cytometry. We speculate upon an activation of protein kinase B (PKB) by insulin, which signals increased survival of SW982 cells.By RT-qPCR we show that insulin downregulates IR expression, and a similar trend is observed for IGF1R. Insulin induced no change in c-Myc expression, and induced a downregulation of c-fos after 12 hours. Further, insulin induced a time-dependent trend of increase in IL-6 gene expression. Insulin also induced variation in the expression of the previously accepted reference gene 18S.More tests have to be conducted in order to validate/discard the hypotheses proposed in this study. Including the possible pro-inflammatory actions of insulin in synovial cells and other tissue, mediated through inhibition of HSL. The potential for insulin to induce hyper proliferation and increased survival of synovial cells through activation of PKB, and the potential for insulin to induce expression proliferative and inflammatory genes.

• Skuland, Trine; Feuerherm, Astrid Jullumstrø; Johansen, Berit & Sommerfelt, Randi Magnus (2013). Effects of Toll-like receptor agonists and tumor necrosis factor-a in the SW982 cell model for synovitis. Institutt for Biologi, NTNU. Fulltekst i vitenarkiv
• Siddik, Ahmed; Feuerherm, Astrid Jullumstrø; Sommerfelt, Randi Magnus & Johansen, Berit (2011). IL-1b og TNFa indusert genuttrykk av DKK1 og OPG involverer cPLA2-IVa i SW982 synoviocytter. Institutt for Biologi, NTNU. Fulltekst i vitenarkiv
• Sommerfelt, Randi Magnus; Feuerherm, Astrid Jullumstrø; Johansen, Berit & Rohloff, Jens (2007). Biological activity of Rhodiola rosea. Institutt for Biologi. Fulltekst i vitenarkiv
• Sommerfelt, Randi Magnus & Iversen, Tor-Henning (2006). Biological Activity of Rhodiola rosea. NTNU, Institutt for biologi. Fulltekst i vitenarkiv

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