Neuroinflammation-induced downregulation of RAB7 in murine astrocytes disrupts endo-lysosomal homeostasis and induces astrogliosis.

BACKGROUND

Neuroinflammation induces astrogliosis, a process marked by astrocyte hypertrophy, increased migration, and altered protein expression. While these changes involve both up- and downregulation of specific genes, the mechanisms governing protein turnover-particularly degradation-remain poorly understood. Here, we investigated how astrocyte endo-lysosomal function is altered during inflammation and explored the role of key regulators such as RAB7 in this response.

METHODS

We analyzed gene expression datasets from an optic nerve injury model to identify pathways associated with reactive gliosis. RAB7 expression and astrocyte reactivity markers, including β3 integrin and GFAP, were assessed in a postnatal rat model of brain injury to evaluate glial responses during early brain maturation. In vitro, TNF-treated astrocytes were used to evaluate changes in gene and protein expression, RAB GTPase activity, lysosomal function, migration, and reactivity markers. RAB7 was overexpressed in selected experiments to confirm its role. The effects of reactive astrocytes on neurite outgrowth were assessed using co-culture assays.

RESULTS

In silico analysis revealed an alteration in the endo-lysosomal pathway under inflammatory conditions. Consistently, downregulation of active and total RAB7, along with GFAP and β3 integrin upregulation, were observed in TNF-treated astrocytes and in the in vivo injury model. Reduced RAB7 was associated with impaired lysosomal function, enhanced astrocyte migration, and reduced neurite outgrowth in neurons co-cultured with reactive astrocytes. Overexpression of RAB7 protected cells from the effects of inflammation, preventing TNF-induced impairment of lysosomal function, astrocyte migration, and neurite outgrowth.

CONCLUSIONS

Our results suggest that inflammation downregulates RAB7, resulting in the appearance of various traits associated with astrocyte reactivity, such as elevated β3 Integrin and GFAP levels. Moreover, RAB7 overexpression prevents these changes. These findings identify RAB7 as a key regulator of astrogliosis and reveal a mechanistic link between RAB-dependent endo-lysosomal pathways and astrocyte reactivity under inflammatory conditions.