[The Molecular Mechanism of HCQ Reversing Immune Mediators Dysregulation in Severe Infection after Chemotherapy in Acute Myeloid Leukemia and Inducing Programmed Death of Leukemia Cells].

Abstract

Objective: To explore the effects of hydroxychloroquine (HCQ) on immune mediators dysregulation in severe infection after chemotherapy in acute myeloid leukemia (AML) and its molecular mechanism.

Methods: Bone marrow or peripheral blood samples of 36 AML patients with severe infection (AML-SI) and 29 AML patients without infection (AML-NI) after chemotherapy were collected from the First Affiliated Hospital of Gannan Medical University from August 2022 to June 2023. In addition, the peripheral blood of 21 healthy subjects from the same period in our hospital was selected as the control group. The mRNA expressions of CXCL12, CXCR4 and CXCR7 were detected by RT-qPCR technology, and the levels of IL-6, IL-8 and TNF-α were detected by ELISA. Leukemia-derived THP-1 cells were selected and constructed as AML disease model. At the same time, bone marrow mesenchymal stem cells (BM-MSCs) from AML-SI patients were co-cultured with THP-1 cells and divided into Mono group and Co-culture group. THP-1 cells were treated with different concentration gradients of HCQ. The cell proliferation activity was subsequently detected by CCK-8 method and apoptosis was detected by Annexin V/PI double staining flow cytometry. ELISA was used to detect the changes of IL-6, IL-8 and TNF-α levels in the supernatant of the cell co-culture system, RT-qPCR was used to detect the mRNA expression changes of the core members of the CXCL12-CXCR4/7 regulatory axis, and Western blot was used to detect the expressions of apoptosis regulatory molecules and related signaling pathway proteins.

Results: CXCL12, CXCR4, CXCR7, as well as IL-6, IL-8, and TNF-α were all abnormally increased in AML patients, and the increases were more significant in AML-SI patients (P <0.01). Furthermore, there were statistically significant differences between AML-NI patients and AML-SI patients (all P <0.05). HCQ could inhibit the proliferation and induce the apoptosis of THP-1 cells, but the low concentration of HCQ had no significant effect on the killing of THP-1 cells. When THP-1 cells were co-cultured with BM-MSCs of AML patients, the levels of IL-6, IL-8 and TNF-α in the supernatance of Co-culture group were significantly higher than those of Mono group (all P <0.01). After HCQ intervention, the levels of IL-6, IL-8 and TNF-α in cell culture supernatant of Mono group were significantly decreased compared with those before intervention (all P <0.01). Similarly, those of Co-culture group were also significantly decreased (all P <0.001). However, the expression of the core members of the CXCL12-CXCR4/7 regulatory axis was weakly affected by HCQ. HCQ could up-regulate the expression of pro-apoptotic protein Bax, down-regulate the expression of anti-apoptotic protein Bcl-2, as well as simultaneously promote the hydrolytic activation of Caspase-3 when inhibiting the activation level of TLR4/NF-κB pathway, then induce the programmed death of THP-1 cells after intervention.

Conclusion: The core members of CXCL12-CXCR4/7 axis and related cytokines may be important mediators of severe infectious immune disorders in AML patients. HCQ can inhibit cytokine levels to reverse immune mediators dysregulation and suppress malignant biological characteristics of leukemia cells. The mechanisms may be related to regulating the expression of Bcl-2 family proteins, hydrolytically activating Caspase-3 and inhibiting the activation of TLR4/NF-κB signaling pathway.