[Effects of melatonin on PBDE-47-induced abnormal autophagy and apoptosis in PC12 cells]

Melatonin alleviates palmitic acid-induced mitochondrial dysfunction by reducing oxidative stress and enhancing autophagy in bovine endometrial epithelial cells

BACKGROUND

Negative energy balance (NEB) typically occurs in dairy cows after delivery. Cows with a high yield are more likely to experience significant NEB. This type of metabolic imbalance could cause ketosis, which is often accompanied by a decline in reproductive performance. However, the molecular mechanisms underlying NEB have yet to be fully elucidated. During excessive NEB, the body fat is extensively broken down, resulting in the abnormal accumulation of non-esterified fatty acids (NEFAs), represented by palmitic acid (PA), within the uterus. Such an abnormal accumulation has the potential to damage bovine endometrial epithelial cells (BEECs), while the molecular mechanisms underlying its involvement in the PA-induced injury of BEECs remains poorly understood. Melatonin (MT) is recognized for its regulatory role in maintaining the homeostasis of mitochondrial reactive oxygen species (mitoROS). However, little is known as to whether MT could ameliorate the damage incurred by BEECs in response to PA and the molecular mechanism involved.

RESULTS

Analysis showed that 0.2 mmol/L PA stress increased the level of cellular and mitochondrial oxidative stress, as indicated by increased reactive oxygen species (ROS) level. In addition, we observed mitochondrial dysfunction, including abnormal mitochondrial structure and respiratory function, along with a reduction in mitochondrial membrane potential and mitochondrial copy number, and the induction of apoptosis. Notably, we also observed the upregulation of autophagy proteins (PINK, Parkin, LC3B and Ubiquitin), however, the P62 protein was also increased. As we expected, 100 μmol/L of MT pre-treatment attenuated PA-induced mitochondrial ROS and restored mitochondrial respiratory function. Meanwhile, MT pretreatment reversed the upregulation of P62 induced by PA and activated the AMPK-mTOR-Beclin-1 pathway, contributing to an increase of autophagy and decline apoptosis.

CONCLUSIONS

Our findings indicate that PA can induce mitochondrial dysfunction and enhance autophagy in BEECs. In addition, MT is proved to not only reduce mitochondrial oxidative stress but also facilitate the clearance of damaged mitochondria by upregulating autophagy pathways, thereby safeguarding the mitochondrial pool and promoting cellular viability. Our study provides a better understanding of the molecular mechanisms underlying the effect of an excess of NEB on the fertility outcomes of high yielding dairy cows.

BDE-47-induced damage prevented by melatonin in grass carp hepatocytes (L8824)

Polybrominated diphenyl ethers (PBDEs) are toxic to organisms with melatonin (MT) providing protection for tissues and cells against these. This study investigates the mechanism of damage of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and the cellular protection of MT on grass carp hepatocytes. Grass carp hepatocytes were exposed to 25 μmol/L BDE-47 and/or 40 μmol/L MT for 24 h before testing. Acridine orange/ethidium bromide (AO/EB) double fluorescence staining results showed that BDE-47 could induce cell apoptosis. The expression levels of the endoplasmic reticulum (ER) stress-related genes ire1, atf4, grp78, perk, and chop were also significantly up-regulated (P < 0.01). The levels of the apoptosis-related genes caspase3, bax, and caspase9 were significantly up-regulated (P < 0.0001), while the level of bcl-2 was significantly down-regulated (P < 0.01). Compared with the BDE-47 group, the BDE-47 + MT group showed reduced levels of ER and apoptosis of hepatocytes, while the expression of the ER stress-related genes ire1, atf4, grp78, perk, and chop and the apoptosis-related genes caspase3, bax, and caspase9 were down-regulated (P < 0.05), and the level of bcl-2 was up-regulated (P < 0.01). In conclusion, BDE-47 can activate ER and apoptosis in grass carp hepatocytes, while MT can reduce these responses.

[Melatonin inhibits growth and metastasis of MDA-MB-231 breast cancer cells by activating autophagy]

OBJECTIVE

To investigate the effects of melatonin on the growth and metastasis of MDA-MB-231 breast cancer cells and explore the mechanism.

METHODS

MDA-MB-231 cells were treated with 1, 3 or 5 mmol/L melatonin, and the changes in cell proliferation were examined using CCK-8 assay. Colony-forming assay and wound healing assay were used to assess the effects of melatonin treatmnent on colony-forming ability and migration of the cells. Flow cytometry and immunofluoresnce assay were employed to examine apoptosis and positive staining for autophagy-related proteins in the cells treated with 3 mmol/L melatonin. The effects of melatonin treatment alone or in combination with 3-methyladenine (3-MA) on the expressions of the proteins associated with autophagy (LC3, P62 and Beclin1), apoptosis (Bcl2 and Bax) and epithelial-mesenchymal transition (E-cadherin and Snail) were examined with Western blotting.

RESULTS

Melatonin treatment significantly inhibited the proliferation of breast cancer cells in a concentration- and time-dependent manner (P < 0.05), suppressed colony-forming ability and migration (P < 0.01), and promoted apoptosis of the cells (P < 0.01). Melatonin treatment alone significantly increased the expressions of Bax (P < 0.05), E-cadherin, LC3-II/LC3-I, and Beclin1 and lowered the expressions of Bcl2 (P < 0.05), Snail, P62 (P < 0.05), and Bcl2/Bax ratio (P < 0.01) in the cells, and caused enhanced positive staining of Beclin1 protein and attenuated staining of P62 protein. Compared with melatonin treatment alone, melatonin treatment combined with 3-MA significantly decreased the expressions of Beclin1 (P < 0.001), LC3-II/LC3-I (P < 0.05), Bax (P < 0.01), and E-cadherin (P < 0.001) and increased the expressions of Bcl2 (P < 0.05), Snail, and Bcl2/Bax ratio (P < 0.01).

CONCLUSION

Melatonin can induce autophagy of MDA-MB-231 breast cancer cells to inhibit cell proliferation and metastasis and promote cell apoptosis, and suppressing autophagy can weaken the inhibitory effect of melatonin on the growth and metastasis of breast cancer cells.