Astaxanthin suppresses LPS-induced myocardial apoptosis by regulating PTP1B/JNK pathway in vitro

Purpose: Myocardial injury induced by sepsis can increase the patient's mortality, which is an important complication of sepsis. Myocardial Apoptosis plays a key role in septic myocardial injury. Here we explored the potential mechanism of astaxanthin (ATX) inhibiting myocardial Apoptosis induced by lipopolysaccharide (LPS) in vitro.

Methods: The H9C2 cell experiment was conducted in three parts. In the first part, we set up three groups: control group, LPS group (10 µg/ml), a model of septic myocardial injury, and LPS + ATX (5, 10, 30 µM); In the second part, we set up four groups: control group, LPS group, LPS + PTP1B-IN-1, a protein tyrosine Phosphatase 1B (PTP1B) inhibitor, and LPS + PTP1B-IN-1 + ATX; In the third part, we set up four groups: control group, LPS group, LPS + Anisomycin, a c-Jun N-terminal kinase (JNK) activator, and LPS + Anisomycin + ATX. We assessed H9C2 cell viability using the Cell Counting Kit-8 (CCK-8) assay. We observed cell Apoptosis using flow cytometry analysis. We tested the mitochondrial membrane potential (ΔΨm) using JC-1 staining. To identify the molecular targets of ATX, Astaxanthin targets were predicted through the SwissTargetPrediction database. We verified the binding affinity of ATX and its targets using microscale thermophoresis (MST). We investigated the p-JNK expression using immunofluorescence staining. Finally, Western blot was used to evaluate PTP1B, JNK, p-JNK and the mitochondrial apoptosis-associated protein expression.

Results: LPS inhibited H9C2 cell viability in a time-dependent manner and ATX treatment enhances H9C2 cell viability in a concentration dependent manner after LPS administration. ATX inhibited the LPS-induced Apoptosis and loss of mitochondrial membrane potential in H9C2 cells. As predicted by the SwissTargetPrediction database, PTP1B was a potential target of ATX, and the interaction between ATX and PTP1B was further verified by MST. ATX attenuated the LPS-induced protein expression of PTP1B and p-JNK, regardless of PTP1B inhibition. Both immunofluorescence staining and Western blotting showed that ATX suppressed the LPS-induced p-JNK expression in H9C2 cells, regardless of Anisomycin administration. In addition, by adding Anisomycin to overexpress JNK, ATX inhibited the LPS-induced Apoptosis, loss of mitochondrial membrane potential and upregulation of mitochondrial apoptosis-associated proteins in H9C2 cells via JNK signaling.

Conclusion: ATX inhibited LPS-induced mitochondrial Apoptosis of H9C2 cells by PTP1B/JNK pathway and PTP1B was the target of ATX.

Astaxanthin; JNK signaling; Lipopolysaccharide; Mitochondrial apoptosis; Protein tyrosine phosphatase 1B.