Lipopolysaccharide-induced Trigeminal Ganglion Nerve Fiber Damage is Associated with Autophagy Inhibition

by Selleckchem | Dec 09 2023

Objective: This study aimed to determine whether lipopolysaccharide (LPS) induces the loss of corneal nerve fibers in cultured trigeminal ganglion (TG) cells, and the underlying mechanism of LPS-induced TG neurite damage.

Methods: TG neurons were isolated from C57BL/6 mice, and the cell viability and purity were maintained for up to 7 days. Then, they were treated with LPS (1 µg/mL) or the autophagy regulator (autophibib and rapamycin) alone or in combination for 48 h, and the length of neurites in TG cells was examined by the immunofluorescence staining of the neuron-specific protein β3-tubulin. Afterwards, the molecular mechanisms by which LPS induces TG neuron damage were explored.

Results: The immunofluorescence staining revealed that the average length of neurites in TG cells significantly decreased after LPS treatment. Importantly, LPS induced the impairment of autophagic flux in TG cells, which was evidenced by the increase in the accumulation of LC3 and p62 proteins. The pharmacological inhibition of autophagy by autophinib dramatically reduced the length of TG neurites. However, the rapamycin-induced activation of autophagy significantly lessened the effect of LPS on the degeneration of TG neurites.

Conclusion: LPS-induced autophagy inhibition contributes to the loss of TG neurites.

Comments:

Title: **Lipopolysaccharide-Induced Autophagy Inhibition Leads to Trigeminal Ganglion Neurite Loss**

**Abstract:**

This study investigates the impact of lipopolysaccharide (LPS) on corneal nerve fibers in cultured trigeminal ganglion (TG) cells and delves into the underlying mechanisms of LPS-induced TG neurite damage. Isolated TG neurons from C57BL/6 mice were exposed to LPS (1 µg/mL) and autophagy regulators (autophinib and rapamycin) either alone or in combination for 48 hours. Neurite length in TG cells was assessed using immunofluorescence staining for the neuron-specific protein β3-tubulin. Our results indicate a significant reduction in neurite length in TG cells following LPS treatment. Furthermore, LPS-induced impairment of autophagic flux in TG cells was observed, as evidenced by the accumulation of LC3 and p62 proteins. Pharmacological inhibition of autophagy with autophinib exacerbated TG neurite degeneration. Conversely, rapamycin-induced autophagy activation mitigated the adverse effects of LPS on TG neurite integrity. Collectively, our findings suggest that LPS-induced inhibition of autophagy contributes to the loss of TG neurites, shedding light on potential therapeutic targets for conditions involving corneal nerve damage.

**Keywords:** Lipopolysaccharide, Trigeminal Ganglion Neurons, Autophagy, Neurite Degeneration, Corneal Nerve Damage.

**Introduction:**

Corneal nerve damage is a significant clinical concern, and understanding the mechanisms underlying this damage is crucial for developing effective therapeutic strategies. Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, has been implicated in various neuroinflammatory processes. In this study, we explored the impact of LPS on trigeminal ganglion (TG) neurites and investigated the role of autophagy in this process. Autophagy, a cellular process crucial for maintaining cellular homeostasis, has been implicated in neurodegenerative disorders and neuronal damage. We hypothesized that LPS-induced inhibition of autophagy contributes to the loss of TG neurites.

**Methods:**

1. **Isolation and Culture of Trigeminal Ganglion (TG) Neurons:**
TG neurons were isolated from C57BL/6 mice and cultured, ensuring viability and purity for up to 7 days.

2. **LPS Treatment and Autophagy Modulation:**
TG cells were treated with LPS (1 µg/mL) and/or autophagy regulators (autophinib and rapamycin) for 48 hours.

3. **Immunofluorescence Staining:**
Neurite length in TG cells was assessed by immunofluorescence staining for the neuron-specific protein β3-tubulin.

4. **Assessment of Autophagic Flux:**
Autophagic flux in TG cells was evaluated by measuring the levels of LC3 and p62 proteins.

**Results:**

1. LPS treatment significantly reduced the average length of neurites in TG cells, indicating neurite degeneration.

2. LPS-induced impairment of autophagic flux was observed, as evidenced by the accumulation of LC3 and p62 proteins in TG cells.

3. Pharmacological inhibition of autophagy with autophinib exacerbated the degeneration of TG neurites in the presence of LPS.

4. Rapamycin-induced activation of autophagy mitigated the adverse effects of LPS on TG neurite integrity.

**Conclusion:**

Our findings suggest that LPS-induced inhibition of autophagy contributes to the loss of TG neurites. Understanding the mechanisms underlying corneal nerve damage is crucial for developing targeted therapies to alleviate neuroinflammatory conditions affecting the cornea. Further research into autophagy modulation could provide valuable insights into the development of novel treatments for corneal nerve-related disorders.