Blockade of Na+/H+ exchanger type 3 causes intracellular acidification and hyperexcitability via inhibition of pH-sensitive K+ channels in chemosensitive respiratory neurons of the dorsal vagal nucleus in rats

Hydrogen Ion Dynamics as the Fundamental Link between Neurodegenerative Diseases and Cancer: Its Application to the Therapeutics of Neurodegenerative Diseases with Special Emphasis on Multiple Sclerosis

The pH-related metabolic paradigm has rapidly grown in cancer research and treatment. In this contribution, this recent oncological perspective has been laterally assessed for the first time in order to integrate neurodegeneration within the energetics of the cancer acid-base conceptual frame. At all levels of study (molecular, biochemical, metabolic, and clinical), the intimate nature of both processes appears to consist of opposite mechanisms occurring at the far ends of a physiopathological intracellular pH/extracellular pH (pHi/pHe) spectrum. This wide-ranging original approach now permits an increase in our understanding of these opposite processes, cancer and neurodegeneration, and, as a consequence, allows us to propose new avenues of treatment based upon the intracellular and microenvironmental hydrogen ion dynamics regulating and deregulating the biochemistry and metabolism of both cancer and neural cells. Under the same perspective, the etiopathogenesis and special characteristics of multiple sclerosis (MS) is an excellent model for the study of neurodegenerative diseases and, utilizing this pioneering approach, we find that MS appears to be a metabolic disease even before an autoimmune one. Furthermore, within this paradigm, several important aspects of MS, from mitochondrial failure to microbiota functional abnormalities, are analyzed in depth. Finally, and for the first time, a new and integrated model of treatment for MS can now be advanced.

Locus Coeruleus Acid-Sensing Ion Channels Modulate Sleep-Wakefulness and State Transition from NREM to REM Sleep in the Rat

The locus coeruleus (LC) is one of the essential chemoregulatory and sleep-wake (S-W) modulating centers in the brain. LC neurons remain highly active during wakefulness, and some implicitly become silent during rapid eye movement (REM) sleep. LC neurons are also involved in CO₂-dependent modulation of the respiratory drive. Acid-sensing ion channels (ASICs) are highly expressed in some brainstem chemosensory breathing regulatory areas, but their localization and functions in the LC remain unknown. Mild hypercapnia increases the amount of non-REM (NREM) sleep and the number of REM sleep episodes, but whether ASICs in the LC modulate S-W is unclear. Here, we investigated the presence of ASICs in the LC and their role in S-W modulation and the state transition from NREM to REM sleep. Male Wistar rats were surgically prepared for chronic polysomnographic recordings and drug microinjections into the LC. The presence of ASIC-2 and ASIC-3 in the LC was immunohistochemically characterized. Microinjections of amiloride (an ASIC blocker) and APETx2 (a blocker of ASIC-2 and -3) into the LC significantly decreased wakefulness and REM sleep, but significantly increased NREM sleep. Mild hypercapnia increased the amount of NREM and the number of REM episodes. However, APETx2 microinjection inhibited this increase in REM frequency. These results suggest that the ASICs of LC neurons modulate S-W, indicating that ASICs could play an important role in vigilance-state transition. A mild increase in CO₂ level during NREM sleep sensed by ASICs could be one of the determinants of state transition from NREM to REM sleep.

Cellular acidification as a new approach to cancer treatment and to the understanding and therapeutics of neurodegenerative diseases

During the last few years, the understanding of the dysregulated hydrogen ion dynamics and reversed proton gradient of cancer cells has resulted in a new and integral pH-centric paradigm in oncology, a translational model embracing from cancer etiopathogenesis to treatment. The abnormalities of intracellular alkalinization along with extracellular acidification of all types of solid tumors and leukemic cells have never been described in any other disease and now appear to be a specific hallmark of malignancy. As a consequence of this intracellular acid-base homeostatic failure, the attempt to induce cellular acidification using proton transport inhibitors and other intracellular acidifiers of different origins is becoming a new therapeutic concept and selective target of cancer treatment, both as a metabolic mediator of apoptosis and in the overcoming of multiple drug resistance (MDR). Importantly, there is increasing data showing that different ion channels contribute to mediate significant aspects of cancer pH regulation and etiopathogenesis. Finally, we discuss the extension of this new pH-centric oncological paradigm into the opposite metabolic and homeostatic acid-base situation found in human neurodegenerative diseases (HNDDs), which opens novel concepts in the prevention and treatment of HNDDs through the utilization of a cohort of neural and non-neural derived hormones and human growth factors.