Elia Ranzato1, Simona Martinotti1, Andrea Volante2, Aldo Tava3, Maria Angela Masini1, Bruno Burlando4. 1. Dipartimento di Scienze e Innovazione Tecnologica (DISIT), Università del Piemonte Orientale, viale T. Michel 11, 15121, Alessandria, Italy. 2. Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria - Rice Research Unit (CREA-RIS), SS 11 per Torino, km 2.5, 13100, Vercelli, Italy. 3. Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria - Centro di Ricerca Zootecnia e Acquacoltura (CREA-ZA), Viale Piacenza 29, 26900, Lodi, Italy. 4. Dipartimento di Farmacia, Università di Genova, Viale Benedetto XV 3, 16132, Genova, Italy; Istituto di Biofisica, CNR, via De Marini 6, 16149, Genova, Italy. Electronic address: burlando@difar.unige.it.
Abstract
BACKGROUND: Boswellia serrata gum resin has attracted pharmacological interest as an alternative antinflammatory. PURPOSE: We studied the application of an ethanolic extract of the resin and its main active 3-O-acetyl-11-keto-β-boswellic acid (AKBA) against inflammatory degeneration of skin extracellular matrix. STUDY DESIGN: We compared the effects of the extract and AKBA on the activity of MMP-2 and MMP-9 (72-kDa and 92-kDa type IV collagenases) in HaCaT keratinocytes exposed to interleukin-1α (IL-1α) as a skin inflammation model. METHODS: MMP activity in cell conditioned medium was assayed by gelatin zymography, while NF-kB and MAP kinase activations were evaluated by Western blotting. RESULTS: IL-1α (10 ng/ml) upregulated MMP-9 but not MMP-2 in HaCaT cells. The extract, used at 2.3, 4.6 and 9.3 µg/ml, had no effect, but in combination with IL-1α showed MMP-9 inhibition at the lowest dose and increased upregulation at the highest one. AKBA alone, at the same concentrations (corresponding to 5, 10, and 20 µM), did not stimulate MMP-9, but together with IL-1α induced an increased upregulation at the lowest dose that progressively disappeared at higher doses. WB analysis showed that IL-1α induced phosphorylation of NF-κB p65, while AKBA abolished this effect at 20 µM, but conversely increased it at 5 µM. Screening of MAP kinase phosphorylation showed a combined activation of IL-1α/AKBA on JNK, while the JNK inhibitor SP600125 abolished MMP-9 upregulation induced by IL-1α/AKBA. CONCLUSION: The enhancing effect of IL-1α/AKBA on MMP-9 at low AKBA concentration seems to involve the activation of JNK-mediated NF-κB pathway. Conversely, the extract inhibits the IL-1α effect at low doses, but not at higher ones, where AKBA and possibly other β-boswellic acids reach concentrations that potentiate the effect of IL-1α. The extract at low doses could protect the skin against degenerative processes of extracellular matrix, while keto-β-boswellic acids seem unsuitable for this purpose.
BACKGROUND:Boswellia serrata gum resin has attracted pharmacological interest as an alternative antinflammatory. PURPOSE: We studied the application of an ethanolic extract of the resin and its main active 3-O-acetyl-11-keto-β-boswellic acid (AKBA) against inflammatory degeneration of skin extracellular matrix. STUDY DESIGN: We compared the effects of the extract and AKBA on the activity of MMP-2 and MMP-9 (72-kDa and 92-kDa type IV collagenases) in HaCaT keratinocytes exposed to interleukin-1α (IL-1α) as a skin inflammation model. METHODS:MMP activity in cell conditioned medium was assayed by gelatin zymography, while NF-kB and MAP kinase activations were evaluated by Western blotting. RESULTS: IL-1α (10 ng/ml) upregulated MMP-9 but not MMP-2 in HaCaT cells. The extract, used at 2.3, 4.6 and 9.3 µg/ml, had no effect, but in combination with IL-1α showed MMP-9 inhibition at the lowest dose and increased upregulation at the highest one. AKBA alone, at the same concentrations (corresponding to 5, 10, and 20 µM), did not stimulate MMP-9, but together with IL-1α induced an increased upregulation at the lowest dose that progressively disappeared at higher doses. WB analysis showed that IL-1α induced phosphorylation of NF-κB p65, while AKBA abolished this effect at 20 µM, but conversely increased it at 5 µM. Screening of MAP kinase phosphorylation showed a combined activation of IL-1α/AKBA on JNK, while the JNK inhibitor SP600125 abolished MMP-9 upregulation induced by IL-1α/AKBA. CONCLUSION: The enhancing effect of IL-1α/AKBA on MMP-9 at low AKBA concentration seems to involve the activation of JNK-mediated NF-κB pathway. Conversely, the extract inhibits the IL-1α effect at low doses, but not at higher ones, where AKBA and possibly other β-boswellic acids reach concentrations that potentiate the effect of IL-1α. The extract at low doses could protect the skin against degenerative processes of extracellular matrix, while keto-β-boswellic acids seem unsuitable for this purpose.