Conclusion
We demonstrated that METP NPs are effective and highly specific regulators of m[Ca2+] overload. In addition, we demonstrated that these METP NPs reverse the macrophage proinflammatory phenotype by restoring m[Ca2+] homeostasis, thereby inhibiting the tissue inflammatory response and achieving a therapeutic effect for OA.
Methods
m[Ca2+] overload in OA mouse bone marrow-derived macrophages (BMDMs) was detected by a fluorescence probe. A tissue in situ fluorescence colocalization assay was used to evaluate METP NP uptake by macrophages. BMDMs from healthy mice were pretreated with a concentration gradient of METP NPs followed by lipopolysaccharide (LPS) stimulation and detection of m[Ca2+] levels in vitro. The optimal METP NP concentration was further applied, and the endoplasmic reticulum (ER) and cytoplasm calcium levels were detected. The inflammatory phenotype was measured by surface markers, cytokine secretion and intracellular inflammatory gene/protein expression. A Seahorse cell energy metabolism assay was performed to elucidate the mechanism by which METP NPs reverse the BMDM proinflammatory phenotype.
Results
The present study identified calcium overload in BMDM mitochondria of OA mice. We demonstrated that METP NPs reversed the increased m[Ca2+] levels in mitochondria and the proinflammatory phenotype of BMDMs, with both in vivo and in vitro experiments, via the inhibition of the mitochondrial aspartate-arginosuccinate shunt and ROS production.