Sensory neuron dysfunction in orthotopic mouse models of colon cancer

Abstract

Reports of neurological sequelae related to colon cancer are largely restricted to rare instances of paraneoplastic syndromes, due to autoimmune reactions. Systemic inflammation associated with tumor development influences sensory neuron function in other disease models, though the extent to which this occurs in colorectal cancer is unknown. We induced orthotopic colorectal cancer via orthotopic injection of two colorectal cancer cell lines (MC38 and CT26) in two different mouse strains (C57BL/6 and Balb/c, respectively). Behavioral tests of pain sensitivity and activity did not detect significant alterations in sensory sensitivity or diminished well-being throughout tumor development. However, immunohistochemistry revealed widespread reductions in intraepidermal nerve fiber density in the skin of tumor-bearing mice. Though loss of nerve fiber density was not associated with increased expression of cell injury markers in dorsal root ganglia, lumbar dorsal root ganglia neurons of tumor-bearing animals showed deficits in mitochondrial function. These neurons also had reduced cytosolic calcium levels in live-cell imaging and reduced spontaneous activity in multi-electrode array analysis. Bulk RNA sequencing of DRGs from tumor-bearing mice detected activation of gene expression pathways associated with elevated cytokine and chemokine signaling, including CXCL10. This is consistent with the detection of CXCL10 (and numerous other cytokines, chemokines and growth factors) in MC38 and CT26 cell-conditioned media, and the serum of tumor-bearing mice. Our study demonstrates in a pre-clinical setting that colon cancer is associated with latent sensory neuron dysfunction and implicates cytokine/chemokine signaling in this process. These findings may have implications for determining risk factors and treatment responsiveness related to neuropathy in colorectal cancer.

Neuromuscular Polytrauma Pain is Resolved by Macrophage COX-2 Nanoimmunomodulation

“…NIRF-NE / CD68 quantification was determined by drawing regions of interest around the relevant tissues and setting an intensity threshold for positive staining that was applied consistently across all images, as described previously. 30 , 42 …”

“…Lysates were then incubated with Mouse Cytokine XL Proteome Profile arrays (Biotechne) according to the manufacturer’s instructions and as described previously. 30 , 42 Chemiluminescent signal was detected using an Amersham ImageQuant 800 blot scanner and ImageQuant TL toolbox v8.2.0 software (GE Healthcare Bio-Sciences). The mean chemiluminescent intensity for each factor was used to calculate the fold-change in abundance due to injury for each factor.…”

Neuromuscular Polytrauma Pain is Resolved by Macrophage COX-2 Nanoimmunomodulation

“…3-4 different sections were imaged from the same mouse. NIRF-NE / CD68 quanti cation was determined by drawing regions of interest around the relevant tissues and setting an intensity threshold for positive staining that was applied consistently across all images, as described previously [30,42].…”

“…Tissues were homogenized in RIPA buffer containing 1% Triton X-100 and Halt Protease Inhibitor Cocktail (Thermo Fisher). Lysates were then incubated with Mouse Cytokine XL Proteome Pro le arrays (Biotechne) according to the manufacturer's instructions and as described previously [30,42]. Chemiluminescent signal was detected using an Amersham ImageQuant 800 blot scanner and ImageQuant TL toolbox v8.2.0 software (GE Healthcare Bio-Sciences).…”

Recent advances in understanding neuronal diversity and neural circuit complexity across different brain regions using single-cell sequencing

“…Dorsal root ganglion neurons, as an important type of sensory neurons, are involved in the generation, transmission, as well as regulation of different somatosensory signals. In turn, their dysfunction occurs in a variety of neuronal diseases ( Nascimento et al, 2018 ; Meltzer et al, 2021 ; Balogh et al, 2022 ). Li et al (2016) have categorized large and small diameter somatosensory neurons in the mouse DRG.…”