Harpagoside

Inhibitory effects of harpagoside on TNF-α-induced pro-inflammatory adipokine expression through PPAR-γ activation in 3T3-L1 adipocytes.[Pubmed: 26049170 ]

Cytokine, 2015, 76(2):368-74.

Obesity is closely associated with increased production of pro-inflammatory adipokines, including interleukin (IL)-6, plasminogen activator inhibitor (PAI)-1, and adipose-tissue-derived monocyte chemoattractant protein (MCP)-1, which contribute to chronic and low-grade inflammation in adipose tissue. Harpagoside, a major iridoid glycoside present in devil's claw, has been reported to show anti-inflammatory activities by suppression of lipopolysaccharide (LPS)-induced production of inflammatory cytokines in murine macrophages. The present study is aimed to investigate the effects of Harpagoside on both tumor necrosis factor (TNF)-α-induced inflammatory adipokine expression and its underlying signaling pathways in differentiated 3T3-L1 cells.
METHODS AND RESULTS:
Harpagoside significantly inhibited TNF-α-induced mRNA synthesis and protein production of the atherogenic adipokines including IL-6, PAI-1, and MCP-1. Further investigation of the molecular mechanism revealed that pretreatment with Harpagoside activated peroxisome proliferator-activated receptor (PPAR)-γ.
CONCLUSIONS:
These findings suggest that the clinical application of medicinal plants which contain Harpagoside may lead to a partial prevention of obesity-induced atherosclerosis by attenuating inflammatory responses.

Harpagoside suppresses lipopolysaccharide-induced iNOS and COX-2 expression through inhibition of NF-kappa B activation.[Pubmed: 16203115]

J Ethnopharmacol. 2006 Mar 8;104(1-2):149-55.

Preparations of Harpagophytum procumbens, known as devil's claw, are used as an adjunctive therapy for the treatment of pain and osteoarthritis. Pharmacological evaluations have proven the effectiveness of this herbal drug as an anti-inflammatory and analgesic agent.
METHODS AND RESULTS:
The present study has investigated the mechanism of action of Harpagoside, one of the major components of Harpagophytum procumbens, using human HepG2 hepatocarcinoma and RAW 264.7 macrophage cell lines. Harpagoside inhibited lipopolysaccharide-induced mRNA levels and protein expression of cyclooxygenase-2 and inducible nitric oxide in HepG2 cells. These inhibitions appeared to correlate with the suppression of NF-kappaB activation by Harpagoside, as pre-treating cells with Harpagoside blocked the translocation of NF-kappaB into the nuclear compartments and degradation of the inhibitory subunit IkappaB-alpha. Furthermore, Harpagoside dose-dependently inhibited LPS-stimulated NF-kappaB promoter activity in a gene reporter assay in RAW 264.7 cells, indicating that Harpagoside interfered with the activation of gene transcription.
CONCLUSIONS:
These results suggest that the inhibition of the expression of cyclooxygenase-2 and inducible nitric oxide by Harpagoside involves suppression of NF-kappaB activation, thereby inhibiting downstream inflammation and subsequent pain events.

Harpagoside Inhibits RANKL-Induced Osteoclastogenesis via Syk-Btk-PLCγ2-Ca(2+) Signaling Pathway and Prevents Inflammation-Mediated Bone Loss.[Pubmed: 26308264 ]

J Nat Prod. 2015 Sep 25;78(9):2167-74.

Harpagoside (HAR) is a natural compound isolated from Harpagophytum procumbens (devil's claw) that is reported to have anti-inflammatory effects; however, these effects have not been investigated in the context of bone development.
METHODS AND RESULTS:
The current study describes for the first time that HAR inhibits receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis in vitro and suppresses inflammation-induced bone loss in a mouse model.HAR also inhibited the formation of osteoclasts from mouse bone marrow macrophages (BMMs) in a dose-dependent manner as well as the activity of mature osteoclasts, including filamentous actin (F-actin) ring formation and bone matrix breakdown. This involved a HAR-induced decrease in extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinase (JNK) phosphorylation, leading to the inhibition of Syk-Btk-PLCγ2-Ca(2+) in RANKL-dependent early signaling, as well as the activation of c-Fos and nuclear factor of activated T cells cytoplasmic 1 (NFATc1), which resulted in the down-regulation of various target genes. Consistent with these in vitro results, HAR blocked lipopolysaccharide (LPS)-induced bone loss in an inflammatory osteoporosis model. However, HAR did not prevent ovariectomy-mediated bone erosion in a postmenopausal osteoporosis model.
CONCLUSIONS:
These results suggest that HAR is a valuable agent against inflammation-related bone disorders but not osteoporosis induced by hormonal abnormalities.

Harpagoside attenuates MPTP/MPP⁺ induced dopaminergic neurodegeneration and movement disorder via elevating glial cell line-derived neurotrophic factor.[Pubmed: 22192054]

J Neurochem. 2012 Mar;120(6):1072-83.

Parkinson's disease is a chronic neurodegenerative movement disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. New therapeutic approaches aiming at delaying or reversing the neurodegenerative process are under active investigations. In this work, we found that Harpagoside, an iridoid purified from the Chinese medicinal herb Scrophularia ningpoensis, could not only prevent but also rescue the dopaminergic neurodegeneration in MPTP/MPP(+) intoxication with promising efficacy.
METHODS AND RESULTS:
Firstly, in cultured mesencephalic neurons, Harpagoside significantly attenuated the loss of TH-positive neuron numbers and the shortening of axonal length. Secondly, in a chronic MPTP mouse model, Harpagoside dose-dependently improved the loco-motor ability (rotarod test), increased the TH-positive neuron numbers in the substantia nigra pars compacta (unbiased stereological counting) and increased the striatal DAT density ((125) I-FP-CIT autoradiography). Thirdly, Harpagoside markedly elevated the GDNF mRNA and GDNF protein levels in MPTP/MPP(+) lesioned models. However, the protecting effect of Harpagoside on the dopaminergic degeneration disappeared when the intrinsic GDNF action was blocked by either the Ret inhibitor PP1 or the neutralizing anti-GDNF antibody.
CONCLUSIONS:
Taken together, we conclude that Harpagoside attenuates the dopaminergic neurodegeneration and movement disorder mainly through elevating glial cell line-derived neurotrophic factor.

Harpagoside ameliorates the amyloid-β-induced cognitive impairment in rats via up-regulating BDNF expression and MAPK/PI3K pathways.[Pubmed: 26135675]

Neuroscience. 2015 Sep 10;303:103-14.

So far, no effective disease-modifying therapies for Alzheimer's disease (AD) aiming at protecting or reversing neurodegeneration of the disease have been established yet. The present work aims to elucidate the effect of Harpagoside (abbreviated HAR), an iridoid glycosides purified from the Chinese medicinal herb Scrophularia ningpoensis, on neurodegeneration induced by β-amyloid peptide (Aβ) and the underlying molecular mechanism.
METHODS AND RESULTS:
Here we show that HAR exerts neuroprotective effects against Aβ neurotoxicity. Rats injected aggregated Aβ₁₋₄₀ into the bilateral hippocampus displayed impaired spatial learning and memory ability in a Y-maze test and novel object recognition test, while HAR treatment ameliorated Aβ₁₋₄₀-induced behavioral deficits. Moreover, administration of HAR increased the expression levels of brain-derived neurotrophic factor (BDNF) and activated the extracellular-regulated protein kinase (ERK) and the phosphatidylinositol 3-kinase (PI3-kinase) pathways both in the cerebral cortex and hippocampus of the Aβ₁₋₄₀-insulted rat model. Furthermore, in cultured primary cortical neurons, Aβ₁₋₄₂ induced significant decrease of choline acetyltransferase (ChAT)-positive neuron number and neurite outgrowth length, both of which were dose dependently increased by HAR. In addition, HAR pretreatment also significantly attenuated the decrease of cell viability in Aβ₁₋₄₂-injured primary cortical neurons. Finally, when K252a, an inhibitor of Trk tyrosine kinases, and a BDNF neutralizing antibody were added to the culture medium 2 h prior to HAR addition, the protective effect of HAR on Aβ₁₋₄₂-induced neurodegeneration in the primary cortical neuron was almost inhibited.
CONCLUSIONS:
Taken together, HAR exerting neuroprotection effect and ameliorating learning and memory deficit appears to be associated, at least in part, with up-regulation of BDNF content as well as activating its downstream signaling pathways, e.g., MAPK/PI3K pathways. It raises the possibility that HAR has potential to be a therapeutic agent against AD.