Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the selective loss of motor neurons in the brain and spinal cord. Despite extensive research, effective treatments remain limited, highlighting the need to explore novel pathogenic mechanisms. This study investigates the potential role of intracellular pH (pHi) as a secondary contributor to motor neuron death in ALS, focusing on a well-established mouse model expressing the G93A mutation in the superoxide dismutase 1 (SOD1) gene. Apoptosis, a form of programmed cell death, has been implicated in motor neuron degeneration in ALS. Recent findings from cancer biology suggest that apoptosis is highly sensitive to pHi, with lower pHi promoting cell death and higher pHi suppressing it. Given that excitotoxicity due to excessive glutamate and calcium overload are key upstream events in ALS pathology, and that glutamate can induce intracellular acidification in a calcium-dependent manner, we hypothesized that acidification of pHi may occur in motor neurons during disease progression and accelerate neurodegeneration.
To test this hypothesis, two pharmacological agents with opposing effects on pH were used: sodium bicarbonate (NaHCO₃), which alkalinizes both extracellular and intracellular environments, and ammonium chloride (NH₄Cl), which initially acidifies extracellular pH but paradoxically increases intracellular pH through diffusion of ammonia into cells and subsequent proton buffering. The study utilized female G93A-SOD1 transgenic mice bred in a hemizygous fashion and housed under standard conditions approved by the Institutional Animal Care and Use Committee. Mice were randomly assigned to one of four groups: untreated control (n = 14), 30 mM NaHCO₃ (n = 17), 100 mM NaHCO₃ (n = 16), or 50 mM NH₄Cl (n = 14). These concentrations were selected to avoid metabolic disturbances while still producing measurable pH shifts. The compounds were dissolved in drinking water supplemented with low levels of sucrose to improve palatability.
Motor function was assessed using the rotarod test starting at postnatal day 85, when all mice were trained to maintain balance for 4 minutes. Performance was monitored weekly until endpoint—defined as falling within 5 seconds in three consecutive trials spaced 2 minutes apart. Body weight, muscle weakness, paralysis, and urine pH were also recorded throughout the experiment. Survival data were analyzed using one-way ANOVA with post hoc Dunnett’s tests, and significance was set at p < 0.1,2-Di(pyridin-4-yl)disulfane site 05. Data are presented as mean ± SEM.
Results showed that both NaHCO₃ and NH₄Cl significantly extended lifespan compared to controls.Saxagliptin Data Sheet The 50 mM NH₄Cl group lived 151.PMID:35101234 93 ± 4.28 days—a 13% increase (p = 0.002)—while the 30 mM NaHCO₃ group survived 145.29 ± 2.23 days (p = 0.047). No significant difference was observed between the two treatment groups, nor did NaHCO₃ show a dose-dependent effect between 30 and 100 mM. Kaplan-Meier survival analysis confirmed a rightward shift in treated groups, with NH₄Cl showing statistically significant improvement (log-rank p = 0.021). Motor function declined similarly across groups over time, with no significant difference between NH₄Cl-treated and control mice. Weight loss, tremor, and paralysis were present in all groups without statistical variation. Urine pH slightly shifted: 6.08 ± 0.042 in NH₄Cl, 6.69 ± 0.063 in 100 mM NaHCO₃, and 6.36 ± 0.05 in controls, with a significant difference between NH₄Cl and NaHCO₃ groups (p = 0.023), yet all values remained within normal physiological ranges.
Discussion centers on the paradoxical efficacy of agents that alter pHe in opposite directions. While NaHCO₃ raises pHe and NH₄Cl lowers it, both extend survival—suggesting a common mechanism related to intracellular pH regulation. Elevated pHe could theoretically enhance NMDA receptor-mediated calcium influx, potentially worsening excitotoxicity. Similarly, decreased pHe might activate acid-sensing ion channels (ASICs), recently found upregulated in ALS patients and G93A mice, contributing to neuronal damage. Additionally, changes in extracellular pH may impair glycine receptor function, increasing excitability. Therefore, the beneficial outcomes are most likely attributable to the shared ability of both compounds to alkalinize pHi. This finding points to pHi modulation as a critical factor in ALS pathogenesis, possibly influencing survival more than motor performance. Future studies should directly measure pHi in motor neurons using techniques such as magnetic resonance spectroscopy to confirm this mechanism. This proof-of-concept study demonstrates a 13% increase in lifespan in a widely used ALS mouse model, representing one of the most robust results reported under similar experimental conditions. These findings highlight an overlooked biochemical pathway that warrants further investigation as a potential therapeutic target in ALS.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com