LRRK2 kinase plays a critical role in manganese-induced inflammation and apoptosis in microglia

Abstract

Long-term exposure to elevated levels of manganese (Mn) causes manganism, a neurodegenerative disorder with Parkinson’s disease (PD)-like symptoms. Increasing evidence suggests that leucine-rich repeat kinase 2 (LRRK2), which is highly expressed in microglia and macrophages, contributes to the inflammation and neurotoxicity seen in autosomal dominant and sporadic PD. As gene-environment interactions have emerged as important modulators of PD-associated toxicity, LRRK2 may also mediate Mn-induced inflammation and pathogenesis. In this study, we investigated the role of LRRK2 in Mn-induced toxicity using human microglial cells (HMC3), LRRK2-wild-type (WT) and LRRK2-knockout (KO) RAW264.7 macrophage cells. Results showed that Mn activated LRRK2 kinase by phosphorylation of its serine residue at the 1292 position (S1292) as a marker of its kinase activity in macrophage and microglia, while inhibition with GSK2578215A (GSK) and MLi-2 abolished Mn-induced LRRK2 activation. LRRK2 deletion and its pharmacological inhibition attenuated Mn-induced apoptosis in macrophages and microglia, along with concomitant decreases in the pro-apoptotic Bcl-2-associated X (Bax) protein. LRRK2 deletion also attenuated Mn-induced production of reactive oxygen species (ROS) and the pro-inflammatory cytokine TNF-α. Mn-induced phosphorylation of mitogen-activated protein kinase (MAPK) p38 and ERK signaling proteins was significantly attenuated in LRRK2 KO cells and GSK-treated cells. Moreover, inhibition of MAPK p38 and ERK as well as LRRK2 attenuated Mn-induced oxidative stress and cytotoxicity. These findings suggest that LRRK2 kinase activity plays a critical role in Mn-induced toxicity via downstream activation of MAPK signaling in macrophage and microglia. Collectively, these results suggest that LRRK2 could be a potential molecular target for developing therapeutics to treat Mn-related neurodegenerative disorders.

LRRK2 regulation of immune-pathways and inflammatory disease

“…LRRK2 has been shown to bind to and phosphorylate MAP2K-3, -4, -6 and -7 [73,74], with increased kinase activity leading to hyperphosphorylation and dopaminergic neuronal death [75]. More recently, it has been demonstrated that LRRK2 kinase activity plays a critical role in manganese-induced inflammation and toxicity via downstream activation of MAPK signalling in both macrophages and microglia [76].…”

Dietary Antioxidants and Parkinson’s Disease

“…Mutation of the kinase domain of LRRK2, G2019S, exacerbates ROS-induced dopaminergic neuronal death, and application of truncated LRRK2 reverses ROS accumulation and prevents morphological alteration of these neurons [ 52 ]. In the same way, the depletion of LRRK2 or application of LRRK2 inhibitors decreases ROS, restores mitochondrial function, prevents mitochondrial fragmentation, and blocks increases in proapoptotic proteins including caspase 3, Bax, and apoptotic-inducing factor [ 53 , 54 , 55 ].…”

The association between PTX3 and serum manganese levels of welders in comparison with controls: An application of anti-inflammatory biomarker

“…In a study on cell culture, exposure to manganese was shown to play an important role in the development of manganeseinduced oxidative stress, inflammation, and apoptosis in microglia with the LRRK2 molecule. In the present study, the effect on inflammation was realized by the increase in manganese-induced TNF-α production (25).…”