Hydrogen Sulfide Promotes Platelet Autophagy via PDGFR-α/PI3K/Akt Signaling in Cirrhotic Thrombocytopenia.

Background and aims: The role of platelet autophagy in cirrhotic thrombocytopenia (CTP) remains unclear. This study aimed to investigate the impact of platelet autophagy in CTP and elucidate the regulatory mechanism of hydrogen sulfide (H₂S) on platelet autophagy.

Methods: Platelets from 56 cirrhotic patients and 56 healthy individuals were isolated for in vitro analyses. Autophagy markers (ATG7, BECN1, LC3, and SQSTM1) were quantified using enzyme-linked immunosorbent assay, while autophagosomes were visualized through electron microscopy. Western blotting was used to assess the autophagy-related proteins and the PDGFR/PI3K/Akt/mTOR pathway following treatment with NaHS (an H₂S donor), hydroxocobalamin (an H₂S scavenger), or AG 1295 (a selective PDGFR-α inhibitor). A carbon tetrachloride-induced cirrhotic BALB/c mouse model was established. Cirrhotic mice with thrombocytopenia were randomly treated with normal saline, NaHS, or hydroxocobalamin for 15 days. Changes in platelet count and aggregation rate were observed every three days.

Results: Cirrhotic patients with thrombocytopenia exhibited significantly decreased platelet autophagy markers and endogenous H₂S levels, alongside increased platelet aggregation, compared to healthy controls. In vitro, NaHS treatment of platelets from severe CTP patients elevated LC3-II levels, reduced SQSTM1 levels, and decreased platelet aggregation in a dose-dependent manner. H₂S treatment inhibited PDGFR, PI3K, Akt, and mTOR phosphorylation. In vivo, NaHS significantly increased LC3-II and decreased SQSTM1 expressions in platelets of cirrhotic mice, reducing platelet aggregation without affecting the platelet count.

Conclusions: Diminished platelet autophagy potentially contributes to thrombocytopenia in cirrhotic patients. H₂S modulates platelet autophagy and functions possibly via the PDGFR-α/PI3K/Akt/mTOR signaling pathway.