Inhibition of leucine-rich repeats and calponin homology domain containing 1 accelerates microglia-mediated neuroinflammation in a rat traumatic spinal cord injury model

Abstract

Background Spinal cord injury (SCI) triggers the primary mechanical injury and secondary inflammation-mediated injury. Neuroinflammation-mediated insult causes secondary and extensive neurological damage after SCI. Microglia play a pivotal role in the initiation and progression of post-SCI neuroinflammation. Methods To elucidate the significance of LRCH1 to microglial functions, we applied lentivirus-induced LRCH1 knockdown in primary microglia culture and tested the role of LRCH1 in microglia-mediated inflammatory reaction both in vitro and in a rat SCI model. Results We found that LRCH1 was downregulated in microglia after traumatic SCI. LRCH1 knockdown increased the production of pro-inflammatory cytokines such as IL-1β, TNF-α, and IL-6 after in vitro priming with lipopolysaccharide and adenosine triphosphate. Furthermore, LRCH1 knockdown promoted the priming-induced microglial polarization towards the pro-inflammatory inducible nitric oxide synthase (iNOS)-expressing microglia. LRCH1 knockdown also enhanced microglia-mediated N27 neuron death after priming. Further analysis revealed that LRCH1 knockdown increased priming-induced activation of p38 mitogen-activated protein kinase (MAPK) and Erk1/2 signaling, which are crucial to the inflammatory response of microglia. When LRCH1-knockdown microglia were adoptively injected into rat spinal cords, they enhanced post-SCI production of pro-inflammatory cytokines, increased SCI-induced recruitment of leukocytes, aggravated SCI-induced tissue damage and neuronal death, and worsened the locomotor function. Conclusion Our study reveals for the first time that LRCH1 serves as a negative regulator of microglia-mediated neuroinflammation after SCI and provides clues for developing novel therapeutic approaches against SCI.

Immune-responsive gene 1/itaconate activates nuclear factor erythroid 2-related factor 2 in microglia to protect against spinal cord injury in mice

“…Activated microglia can swallow and remove cell debris and release neurotrophic factors [ 31 , 32 ]. On the other hand, over-activated microglia often release a large number of proinflammatory mediators, further aggravating the damage to nerve cells [ 33 , 34 ]. Several studies have shown that regulating the metabolism and inflammation of microglia is beneficial to the survival of nerve cells [ 35 – 37 ].…”

Interleukin 6 reduces vascular smooth muscle cell apoptosis via Prep1 and is associated with aging

“…25 The sections were then subjected to staining with the TUNEL Assay Kit-BrdU-Red (ab66110, Abcam, United Kingdom) following the manufacturer's manual. 26 2.4 | Cell culture procedures and transfection Rat aortic vascular smooth muscle cells (VSMCs) were a kind gift from Prof. G. Iaccarino, "Federico II" University of Naples. Cells were grown in DMEM containing 4.5 g/L glucose supplemented with 10% Fetal Bovine Serum (FBS), 2 mmol/L l-glutamine, 0.1 mmol/L non-essential amino acids, and 1% penicillin/streptomycin solution at 37°C in a humidified 95% air and 5% CO 2 atmosphere (all vol./vol.).…”

Structure and Emerging Functions of LRCH Proteins in Leukocyte Biology

“…In human platelets exposed to E. coli K12 and RAW 264.7 macrophages stimulated with LPS LRCH4 mRNA levels are downregulated (Fejes et al, 2018;Aloor et al, 2019). Microglia isolated from rat spinal cords after spinal cord injury (SCI) express lower levels of LRCH1 mRNA and protein compared to microglia from sham-operated rats (Chen et al, 2020). In human primary macrophages, infection with Staphylococcus aureus, Mycobacterium tuberculosis, Listeria monocytogenes (L. monocytogenes), and enterohemorragic E. coli induces a downregulation of LRCH4, suggesting that LRCH proteins may function as critical effector molecules under inflammatory conditions, especially during host defense (Ng et al, 2011).…”

“…In LRCH1-deficient NK92 cells phosphorylation of these SFKs is increased at basal levels and further increases in presence of tumor cells compared to control cells. Furthermore, LRCH1 negatively regulates activation and function of rat microglia via a p38 mitogen-activated protein kinase (MAPK) and ERK1/2-dependent pathway (Chen et al, 2020). Upon priming with LPS and ATP, LRCH1-knockdown microglia release higher levels of TNFα, IL-6 and IL-1β and develop into a pro-inflammtory phenotype.…”