Polyphenols Extracts from Oil Production Waste Products (OPWPs) Reduce Cell Viability and Exert Anti-Inflammatory Activity via PPARγ Induction in Colorectal Cancer Cells

Abstract

Olive oil production is associated with the generation of oil production waste products (OPWPs) rich in water-soluble polyphenols that represent serious environmental problems. Yet OPWPs can offer new opportunities by exploiting their bioactive properties. In this study, we chemically characterized OPWPs polyphenolic extracts and investigated their biological activities in normal and colorectal cancer cells. Hydroxytyrosol (HTyr), the major constituent of these extracts, was used as the control. We show that both HTyr and the extracts affect cell viability by inducing apoptosis and cell cycle arrest. They downregulate inflammation by impairing NF-κB phosphorylation and expression of responsive cytokine genes, as TNF-α and IL-8, at both mRNA and protein levels, and prevent any further increase elicited by external challenges. Mechanistically, HTyr and the extracts activate PPARγ while hampering pro-inflammatory genes expression, acting as a specific agonist, likely through a trans-repression process. Altogether, OPWPs polyphenolic extracts show stronger effects than HTyr, conceivably due to additive or synergistic effects of all polyphenols contained. They display anti-inflammatory properties and these results may pave the way for improving OPWPs extraction and enrichment methods to reduce the environmental impact and support their use to ameliorate the inflammation associated with diseases and tumors.

Transcriptomic Analysis of Colorectal Cancer Cells Treated with Oil Production Waste Products (OPWPs) Reveals Enrichment of Pathways of Mitochondrial Functionality

“…In order to evaluate the modifications of the complete set of RNA transcripts, we treated CRC HCT116 cells for 72 h with HTyr or OPWPs (0.0154 mg mL −1 ) from Apulia (AE), Tuscany (TE) and Sicily (SE), whose composition has previously been reported [ 25 ]. Total RNA was extracted, purified and subjected to high throughput RNA-sequencing, as specified in the M & M section.…”

“…Consistent with these data, we recently showed that administration of the non-toxic dose of 0.0154 mg mL −1 HTyr, AE, TE and SE to HCT116 cells for 72 h, induced a cell cycle arrest at the G 2 /M phase and impaired cell proliferation. The treatment also elicited an anti-inflammatory response [ 25 ]. This result agrees with the present GSEA analysis that, among the most downregulated pathways, includes TNF-α signaling via NF-κB, TGF-β and IL2-STAT signaling, strongly supporting the anti-inflammatory role of HTyr and OPWPs extracts.…”

“…The three HTyr-enriched OPWPs extracts were produced at different sites across Italy, namely Apulia, Tuscany and Sicily, henceforth named AE (Apulia Extract), TE (Tuscany Extract) and SE (Sicily Extract), respectively. They were characterized as previously reported [ 25 ].…”

“…Oil production waste products (OPWPs) freeze-dried extracts were resuspended in sterile water at the concentration of 100 mg mL −1 (corresponding to their solubility). In all experiments, HCT116 cells were treated with 0.0154 mg mL −1 HTyr or 0.0154 mg mL −1 OPWPs extracts for 72 h; LoVo cells were treated with 0.0231 mg mL −1 HTyr or 0.0231 mg mL −1 OPWPs extracts for 72 h. These values were obtained after assessment of the IC 50 for HTyr in each cell line [ 25 ]. In some experiments, HCT116 and LoVo cells were treated with rosiglitazone (1 µM), a PPARγ-selected agonist or with GW9662 (10 µM), a PPARγ irreversible antagonist, for 72 h (both from Cayman, Ann Arbor, MI, USA) dissolved in dimethyl sulfoxide (DMSO, Merck-Sigma, St. Louis, MO, USA); DMSO alone was used as a vehicle control.…”

In Vitro Anti-Proliferative and Apoptotic Effects of Hydroxytyrosyl Oleate on SH-SY5Y Human Neuroblastoma Cells

“…HTyr displays a variety of biological activities [ 15 ], including antioxidant [ 16 ], anti-inflammatory [ 17 ], anticancer [ 18 , 19 , 20 ], anti-diabetic [ 21 ], cardioprotective [ 22 ], and neuroprotective [ 23 , 24 ] properties. Recent studies have evidenced that HTyr plays a relevant role in the prevention of neurodegenerative diseases [ 25 ], in the neurogenesis of adult and aged mice and in increasing the survival of new neurons [ 26 ].…”