The Conditioned Medium of Lactobacillus rhamnoides GG Regulates Microglia/Macrophage Polarization and Improves Functional Recovery after Spinal Cord Injury in Rats

Lactobacillus rhamnoides, a human intestinal colonizer, can act through various pathways to induce microglia/macrophages to produce cytokines and to polarize microglia/macrophages to different phenotypes to reduce the inflammatory response. In this article, we evaluated the treatment potential of the Lactobacillus rhamnoides GG conditioned medium (LGG-CM) in rat model with SCI (acute spinal cord injury), including functional, neurophysiological, and histological outcomes and the underlying neuroprotective mechanisms. In our experiment, LGG-CM (30 mg/kg) was injected directly into the injury site in rats immediately after SCI. Measured by the BBB scale (Basso, Beattie, and Bresnahan locomotor rating scale) and inclined plane test, rats in the LGG-CM-treated group showed better locomotor scores. Moreover, compared to the vehicle treatment group, LGG-CM increased the mRNA level of the M2 marker (CD206), and decreased that of the M1 marker (iNOS). Western blot assays showed that LGG-CM-treated SCI rats had a higher grayscale ratio of p65 and a lower ratio of p-IκBα/IκBα. Our study shows that local injection of LGG-CM after acute SCI can inhibit inflammatory responses and improve motor function recovery. These effects may be related with the inhibition to the NF-κB (The nuclear factor-kappa B) signal pathway which leads to M2 microglia/macrophage polarization.