Interfering with lysophosphatidic acid receptor edg2/lpa₁ signalling slows down disease progression in SOD1‐G93A transgenic mice

Abstract

Aims: Alterations in excitability represent an early hallmark in Amyotrophic Lateral Sclerosis (ALS). Therefore, deciphering the factors that impact motor neuron (MN) excitability offers an opportunity to uncover further aetiopathogenic mechanisms, neuroprotective agents, therapeutic targets, and/or biomarkers in ALS. Here, we hypothesised that the lipokine lysophosphatidic acid (lpa) regulates MN excitability via the G-proteincoupled receptor lpa 1 . Then, modulating lpa 1 -mediated signalling might affect disease progression in the ALS SOD1-G93A mouse model. Methods:The influence of lpa-lpa 1 signalling on the electrical properties, Ca 2+ dynamic and survival of MNs was tested in vitro. Expression of lpa 1 in cultured MNs and in the spinal cord of SOD1-G93A mice was analysed. ALS mice were chronically treated with a small-interfering RNA against lpa 1 (siRNA lpa1 ) or with the lpa 1 inhibitor AM095. Motor skills, MN loss, and lifespan were evaluated.Results: AM095 reduced MN excitability. Conversely, exogenous lpa increased MN excitability by modulating task1 'leak' potassium channels downstream of lpa 1 . Lpa-lpa 1 signalling evoked an excitotoxic response in MNs via voltage-sensitive calcium channels.Cultured SOD1-G93A MNs displayed lpa 1 upregulation and heightened vulnerability to lpa. In transgenic mice, lpa 1 was upregulated mostly in spinal cord MNs before cell loss. Chronic administration of either siRNA lpa1 or AM095 reduced lpa 1 expression at least in MNs, delayed MN death, improved motor skills, and prolonged life expectancy of ALS mice.Conclusions: These results suggest that stressed lpa-lpa 1 signalling contributes to MN degeneration in SOD1-G93A mice. Consequently, disrupting lpa 1 slows down disease progression. This highlights LPA 1 signalling as a potential target and/or biomarker in ALS.

Lysophosphatidic Acid and Several Neurotransmitters Converge on Rho-Kinase 2 Signaling to Manage Motoneuron Excitability

“…The effects of sLPA were also tested in the in vitro model of brainstem slices from neonatal rats. Addition to the bath solution of sLPA (40 μM) induced a pronounced increase in IME of HMNs from rat pups, characterized by Vm depolarization (+ 11.6 ± 2.4 mV; Figure 5C ), R N increase (+ 32.5 ± 9.8 MΩ), and I th reduction (–0.38 ± 0.06 nA) ( Supplementary Table 6 ), just like we recently reported for the monounsaturated species LPA (18:1) ( Gento-Caro et al, 2021a ). Co-addition to the bath solution of H1152 fully reverted changes in Vm and R N , but not in I th , to control pre-treatment conditions ( Figure 5C and Supplementary Table 6 ).…”

“…For the next step in this study, we looked for evidence of whether ROCK mediates the action of some known physiological regulator of MN IME that targets TASK1. In this framework, one of them is the bioactive phospholipid LPA, whose downstream signaling cascades include ROCK stimulation, among others ( Choi and Chun, 2013 ), and regulates MN IME in a TASK1-dependent manner ( Gento-Caro et al, 2021a , b ). Furthermore, LPA-RhoA/ROCK signaling regulates GABA A receptor subunits composition in MNs ( García-Morales et al, 2015 ), supporting that LPA signaling can increase ROCK activity in this cell type.…”

“…These results confirm that sLPA-induced effects on HMN IME is, at least in part, mediated by ROCK. LPA affects HMN IME by the LPA receptor 1 (LPA 1 ) and LPA 1 -mediated modulation of synaptic neurotransmission in MNs involves G αi/o protein ( García-Morales et al, 2015 ; Gento-Caro et al, 2021a , b ). Therefore, we next inspected whether action of sLPA on HMN IME also relies on this G protein.…”

“…A ROCK-dependent mechanism that impairs traffic of TASK1 to the plasma membrane has also been shown to underlie downregulation of TASK currents following long-term exposure to nitric oxide at pathological concentrations ( García-Morales et al, 2019 ). Furthermore, lysophosphatidic acid (LPA) signaling, an upstream activator of ROCK, increases MN IME in a TASK1-dependent manner ( Gento-Caro et al, 2021a , b ). Finally, immunostaining of the hypoglossal motor nucleus (HN) suggested that ROCK2 is the main isoform expressed in hypoglossal MNs (HMNs; Figure 1A ), whereas ROCK1 is the predominant one in synaptic structures ( González-Forero et al, 2012 ).…”

The linkage between inflammation and fibrosis in muscular dystrophies: The axis autotaxin–lysophosphatidic acid as a new therapeutic target?

“…The positive effects of inhibiting LPA receptors in lung fibrosis were also replicated in the bleomycin induced model (Ohashi and Yamamoto 2015). In the murine model SOD1-G93A that mimics amyotrophic lateral sclerosis (ALS), which causes skeletal muscle fibrosis, the treatment with AM095, an LPA1 inhibitor, causes motor skills improvement evaluated by grip strength, rotarod, and runtime (Gento-Caro et al 2021). These results support the use of inhibitors of the ATX/LPA/LPARs axis in the treatment of fibrotic disorders, as addressed in numerous clinical trials, mainly in idiopathic pulmonary fibrosis and scleroderma.…”