Novel anti-inflammatory actions of nobiletin, a citrus polymethoxy flavonoid, on human synovial fibroblasts and mouse macrophages
Authors: Takashi Sato
Yutaka Sashida
Na Lin
Masamichi Yano
Yoshihiro Mimaki
Akira Ito
Yuji Takayama
Journal: Biochemical pharmacology (2003)
Discipline: PHARMACOLOGY & TOXICOLOGY
Keywords: nobiletin; synovial fibroblasts; COX-2; PGE(2); proinflammatory cytokines

Abstract:  We previously reported that nobiletin (5,6,7,8,3',4'-hexamethoxy flavone), a citrus polymethoxy flavonoid, effectively interferes with the production of promatrix metalloproteinase (proMMP)-9/progelatinase B in rabbit synovial fibroblasts [J. Rheumatol. 27 (2000) 20]. In this paper, we further examine the effects of nobiletin on the production of cyclooxygenases (COXs), prostaglandin (PG) E(2), and proinflammatory cytokines in human synovial fibroblasts and the mouse macrophage J774A.1 cell line. Nobiletin suppressed the interleukin (IL)-1-induced production of PGE(2) in human synovial cells in a dose-dependent manner (&lt;64 microM). Additionally, it selectively downregulated COX-2, but not COX-1 mRNA expression. Nobiletin also interfered with the lipopolysaccharide-induced production of PGE(2) and the gene expression of proinflammatory cytokines including IL-1alpha, IL-1beta, TNF-alpha and IL-6 in mouse J774A.1 macrophages. In addition, nobiletin downregulated the IL-1-induced gene expression and production of proMMP-1/procollagenase-1 and proMMP-3/prostromelysin-1 in human synovial fibroblasts. In contrast, production of the endogenous MMP inhibitor, TIMP-1, was augmented by nobiletin. These anti-inflammatory actions of nobiletin are very similar to those of anti-inflammatory steroids such as dexamethasone, and the upregulation of TIMP-1 production is a unique action of nobiletin. Therefore, these results further support the notion that nobiletin is likely to be a candidate for characterization as a novel immunomodulatory and anti-inflammatory drug. 

Retracted: No

PubPeer comments:
  Fig. 4. Effect of nobiletin on IL-1a, IL-1b, IL-6, and TNF-a gene expression in mouse J774A.1 macrophages. Adherent mouse macrophages, in 60-mm dishes, were treated with LPS (5 mg mL) and or nobiletin (32 mM) in 3.0 mL of RPMI 1640 0.2% LAH for 12 hr. Total RNA (3 mg) was subjected to RT-PCR for the amplification of (A) IL-1a, (B) IL-1b, (C) IL-6, (D) TNF-a, and (E) GAPDH mRNA as described in the text. Treatments: l, control; 2, LPS; and 3, LPS plus nobiletin (32 mM). The vertical discontinuties in the bands for IL-1a, IL-6, and TNF-a leave me unconvinced that those RNAs were examined with all three conditions on the same gel. ![file] , 
 Fig. 6. Time-dependent downregulation by nobiletin of the expression of IL-1a-induced proMMP-1 mRNA in human synovial cells. Confluent synovial cells at passage 7 were treated with rhIL-1a (1 ng mL) and or nobiletin (64 mM) for the indicated periods, and then total RNA was extracted using Isogen. Total RNA (3 mg) was subjected to RT-PCR for the amplification of (A) proMMP-1 and (B) GAPDH mRNA. Treatments: l, control; 2, rhIL-1a; and 3, rhIL-1a plus nobiletin (64 mM). ![file] Horizontal discontinuities in band (A), between the streaks themselves and the background above and below. Is this normal? , 
 #1 *[Right]* Fig 4 again:  Effect of nobiletin on IL-1a, IL-1b, IL-6, and TNF-a gene expression in mouse J774A.1 macrophages. Adherent mouse macrophages, in 60-mm dishes, were treated with LPS (5 mg mL) and or nobiletin (32 mM) in 3.0 mL of RPMI 1640 0.2% LAH for 12 hr. Total RNA (3 mg) was subjected to RTPCR for the amplification of (A) IL-1a, (B) IL-1b, (C) IL-6, (D) TNF-a, and (E) GAPDH mRNA as described in the text. Treatments: l, control; 2, LPS; and 3, LPS plus nobiletin (32 mM). *[Left]* Figure 6 from [Lin et al (2001)] :  Interference by triptolide with gene expression of interleukin-a (IL-1a), IL-1b, IL-6, and tumor necrosis factor a (TNFa) in mouse macrophages. Adherent J774A.1 cells in 60-mm dishes were treated with lipopolysaccharide (LPS; 5 mg ml) and or triptolide (28 nM) in 3 ml RPMI 1640 0.2% lactalbumin hydrolysate for 12 hours. Total RNA (3 mg) was subjected to reverse transcriptaseu2013 polymerase chain reaction for mRNA of IL-1a, IL-1b, TNFa, IL-6, and mouse GAPDH, as described in the text. ![file] The IL-1a, IL-1b, IL-6, and TNF-a blobs seem to be the same in Lane 2 of both Figures (rearranged in sequence). Since both lane-2s represent the same conditions, this is not an issue, but the fact that Lane 1 and Lane 3 differ between the Figures implies that one or other set of bands are composites. Can the authors report if this was the case? (this may not be a reasonable question to ask after the passage of so much time). ,