Nanoscale lipid-methylprednisolone conjugates: Effective anti-inflammatory, antioxidant, and analgesic agents

In this study, we have investigated new lipid-drug conjugates (LDCs) of methylprednisolone. Methylprednisolone is a corticosteroid, used for the potential treatment of inflammatory diseases. The LDCs 1–2; methylprednisolone palmitate (1) and methylprednisolone palmityl carbonate (2), were designed by conjugating a C16 aliphatic chain via an ester or carbonate bond, respectively. Their structures were comprehensively characterized using mass spectrometry, nuclear magnetic resonance spectroscopy, and infrared spectroscopy. These LDCs 1–2 were subsequently formulated into nanoscale particles (NPs) using ethanol injection method. Hydrogenated soybean phosphatidylcholine (HSPC) and tween-80 served as excipients in the NPs formulation. Characterization via dynamic light scattering, scanning electron microscopy, and atomic force microscopy confirmed the formation of spherical NPs with a diameter ranging from 100 to 120 nm. The LDCs NPs 1–2 exhibited excellent stability for about a month, with good polydispersity (around 0.2) and a negative zeta potential between −20 mV and −34 mV. Encapsulation efficiency of the LDCs within the LDCs NPs 1–2 surpassed 90 %, as determined by HPLC analysis. In vitro cytotoxicity studies utilizing LPS-activated THP-1 cells demonstrated no adverse effects associated with LDCs NPs 1–2 at concentrations up to 100 μg/mL. Furthermore, the LDCs NPs 1–2 effectively retained the anti-inflammatory activity, as evidenced by the suppression of IL-1β, TNF-α, and MCP-1 secretion in LPS-stimulated THP-1 cells. The therapeutic potential of these LDCs NPs 1–2 was further evaluated in rat intervertebral disc-derived nucleus pulposus cells (NPCs). Curative and preventive treatment regimens with the free drug and LDCs NPs 1–2 were employed. Quantitative PCR analysis revealed a significant downregulation of pain and inflammation markers (Substance P and COX-2) along with a concomitant upregulation of antioxidant markers (GPX1, PRDX1, and SOD1) in NPCs treated with both the drug and LDCs NPs 1–2 compared to oxidative stress-induced and control NPCs. Our novel LDCs NPs 1–2 exhibited promising therapeutic potential for treating inflammatory and pain related complications, (including intervertebral disc degeneration). This promise stems from their multifaceted properties, encompassing anti-inflammatory, antioxidant, and analgesic effects. Further research is warranted to fully explore LDCs NPs 1–2 as potential drug candidates in future pre-clinical and clinical trials.