Colorectal Cancer Apoptosis Induced by Dietary δ-Valerobetaine Involves PINK1/Parkin Dependent-Mitophagy and SIRT3

Abstract

Understanding the mechanisms of colorectal cancer progression is crucial in the setting of strategies for its prevention. δ-Valerobetaine (δVB) is an emerging dietary metabolite showing cytotoxic activity in colon cancer cells via autophagy and apoptosis. Here, we aimed to deepen current knowledge on the mechanism of δVB-induced colon cancer cell death by investigating the apoptotic cascade in colorectal adenocarcinoma SW480 and SW620 cells and evaluating the molecular players of mitochondrial dysfunction. Results indicated that δVB reduced cell viability in a time-dependent manner, reaching IC50 after 72 h of incubation with δVB 1.5 mM, and caused a G2/M cell cycle arrest with upregulation of cyclin A and cyclin B protein levels. The increased apoptotic cell rate occurred via caspase-3 activation with a concomitant loss in mitochondrial membrane potential and SIRT3 downregulation. Functional studies indicated that δVB activated mitochondrial apoptosis through PINK1/Parkin pathways, as upregulation of PINK1, Parkin, and LC3B protein levels was observed (p < 0.0001). Together, these findings support a critical role of PINK1/Parkin-mediated mitophagy in mitochondrial dysfunction and apoptosis induced by δVB in SW480 and SW620 colon cancer cells.

SIRT3 and Metabolic Reprogramming Mediate the Antiproliferative Effects of Whey in Human Colon Cancer Cells

“…SIRT3 orchestrates multiple pathways and acts differently in various types of cancer cells, as tumor suppressor but also as tumor promoter [18][19][20][21][22][23][24][25][26]. Intriguingly, in CRC, SIRT3 displays an oncogenic role by deacetylating SHMT2 [27], and acts as tumor suppressor by increasing ROS production and PINK1/Parkin/mitophagy axis activation [9]. Results of this study indicated that whey treatment increased the SIRT3 expression levels in HT-29 and HCT 116 cells.…”

“…The mechanism(s) by which nutrients may affect health span and act as nutritional epigenetic modulators is still not fully understood as it involves multiple evolutionary conserved nutrient-sensing pathways interacting each other, such as sirtuins, conserved key regulators mammalian target of rapamycin, AMP-activated protein kinase, insulin/insulinlike growth factor 1, PINK1/Parkin, and mitophagy [1,2,9]. It is undoubtedly hard to define the exact bioactive component of the 3 kDa whey extract, known to be rich in peptides, betaines, L-carnitine, and acylcarnitines [28], especially in light of the synergism among betaines [8].…”

“…The health potential of milk has recently been brought to attention due to its content in δ-valerobetaine and the peculiar metabolomic profile, with regard to the milk from the Italian Mediterranean buffalo (Bubalus bubalis) particularly rich in L-carnitine, short-chain acylcarnitines, and betaines [3][4][5]. The antioxidant, anti-inflammatory and anticancer properties of δ-valerobetaine, acting in synergism with other betaines, occur in endothelial cells, colorectal cancer (CRC) cells and human oral squamous cell carcinoma cells through the modulation of sirtuins [6][7][8][9]. In CRC cells, LoVo and HT-29, the activation of SIRT6 mediated the anticancer and apoptotic activity of milk [7].…”

“…In CRC cells, the chemopreventive effects of 3 kDa-fraction of milk and its biomolecules occur through mitochondrial dysfunction and downregulation of SIRT3 [9]. SIRT3-silenced metastatic CRC cells showed mitochondrial aggregation and ROS accumulation and colony formation ability leading to decreased mitochondrial dysfunction [9,17].…”

“…In CRC cells, the chemopreventive effects of 3 kDa-fraction of milk and its biomolecules occur through mitochondrial dysfunction and downregulation of SIRT3 [9]. SIRT3-silenced metastatic CRC cells showed mitochondrial aggregation and ROS accumulation and colony formation ability leading to decreased mitochondrial dysfunction [9,17]. The imbalanced mitochondrial functions affected cell viability and expression of several proteins related to mitochondrial biogenesis, including the lactate dehydrogenase (LDH) expression [17].…”