High blood pressure induces a mechanical stress on vascular walls and evokes oxidative stress and vascular dysfunction. The aim of this study was to characterize the intracellular signaling causing vascular oxidative stress in response to pressure. In carotid arteries subjected to high pressure levels, we observed not only an impaired vasorelaxation, increased superoxide production, and NADPH oxidase activity, but also a concomitant activation of Rac-1, a small G protein. Selective inhibition of Rac-1, with an adenovirus carrying a dominant-negative Rac-1 mutant, significantly reduced NADPH oxidase activity and oxidative stress and, more importantly, rescued vascular function in carotid arteries at high pressure. The analysis of molecular events associated with mechanotransduction demonstrated at high pressure levels an overexpression of integrin-linked kinase 1 and its recruitment to plasma membrane interacting with paxillin. The inhibition of integrin-linked kinase 1 by small interfering RNA impaired Rac-1 activation and rescued oxidative stress–induced vascular dysfunction in response to high pressure. Finally, we showed that βPIX, a guanine-nucleotide exchange factor, is the intermediate molecule recruited by integrin-linked kinase 1, converging the intracellular signaling toward Rac-1–mediated oxidative vascular dysfunction during pressure overload. Our data demonstrate that biomechanical stress evoked by high blood pressure triggers an integrin-linked kinase 1/βPIX/Rac-1 signaling, thus generating oxidative vascular dysfunction.

Recent studies described a critical role for microglia in amyotrophic lateral sclerosis (ALS), where these CNS-resident immune cells participate in the establishment of an inflammatory microenvironment that contributes to motor neuron degeneration. Understanding the mechanisms leading to microglia activation in ALS could help to identify specific molecular pathways which could be targeted to reduce or delay motor neuron degeneration and muscle paralysis in patients. The intermediate-conductance calcium-activated potassium channel KCa3.1 has been reported to modulate the "pro-inflammatory" phenotype of microglia in different pathological conditions. We here investigated the effects of blocking KCa3.1 activity in the hSOD1(G93A)ALS mouse model, which recapitulates many features of the human disease. We report that treatment of hSOD1(G93A) mice with a selective KCa3.1 inhibitor, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), attenuates the "pro-inflammatory" phenotype of microglia in the spinal cord, reduces motor neuron death, delays onset of muscle weakness, and increases survival. Specifically, inhibition of KCa3.1 channels slowed muscle denervation, decreased the expression of the fetal acetylcholine receptor gamma subunit and reduced neuromuscular junction damage. Taken together, these results demonstrate a key role for KCa3.1 in driving a pro-inflammatory microglia phenotype in ALS.

Background and Purpose: Amyotrophic lateral sclerosis (ALS) patients exhibit dysfunctional energy metabolism and weight loss, which is negatively correlated with survival, together with neuroinflammation. However, the possible contribution of neuroinflammation to deregulations of feeding behaviour in ALS has not been studied in detail. We here investigated if microglial K_Ca3.1 is linked to hypothalamic neuroinflammation and affects feeding behaviours in ALS mouse models.Experimental Approach: hSOD1^G93A and TDP43^A315T mice were treated daily with 120 mg·kg⁻¹ of TRAM‐34 or vehicle by intraperitoneal injection from the presymptomatic until the disease onset phase. Body weight and food intake were measured weekly. The later by weighing food provided minus that left in the cage. RT‐PCR and immunofluorescence analysis were used to characterize microglia phenotype and the main populations of melanocortin neurons in the hypothalamus of hSOD1^G93A and age‐matched non‐tg mice. The cannabinoid–opioid interactions in feeding behaviour of hSOD1^G93A mice were studied using an inverse agonist and an antagonist of the cannabinoid receptor CB₁ (rimonabant) and μ‐opioid receptors (naloxone), respectively.Key Results: We found that treatment of hSOD1^G93A mice with the K_Ca3.1 inhibitor TRAM‐34 (i), attenuates the pro‐inflammatory phenotype of hypothalamic microglia, (ii) increases food intake and promotes weight gain, (iii) increases the number of healthy pro‐opiomelanocortin (POMC) neurons and (iv), changes the expression of cannabinoid receptors involved in energy homeostasis.Conclusion and Implications: Using ALS mouse models, we describe defects in the hypothalamic melanocortin system that affect appetite control. These results reveal a new regulatory role for K_Ca3.1 to counteract weight loss in ALS.

The growing interest in the role of microglia in the progression of many neurodegenerative diseases is developing in an ever-expedited manner, in part thanks to emergent new tools for studying the morphological and functional features of the CNS. The discovery of specific biomarkers of the microglia phenotype could find application in a wide range of human diseases, and creates opportunities for the discovery and development of tailored therapeutic interventions. Among these, recent studies highlight the pivotal role of the potassium channels in regulating microglial functions in physiological and pathological conditions such as Alzheimer’s Disease, Parkinson’s Disease, and Amyotrophic Lateral Sclerosis. In this review, we summarize the current knowledge of the involvement of the microglial potassium channels in several neurodegenerative diseases and their role as modulators of microglial homeostasis and dysfunction in CNS disorders.

Weight loss is a common early sign in amyotrophic lateral sclerosis (ALS) patients and negatively correlates with survival. In different cancers and metabolic disorders, high levels of serum growth differentiation factor 15 (GDF15) contribute to a decrease of food intake and body weight, acting through GDNF family receptor alpha-like (GFRAL). Here we report that GDF15 is highly expressed in the peripheral blood of ALS patients and in the hSOD1^G93A mouse model and that GFRAL is upregulated in the brainstem of hSOD1^G93A mice. We demonstrate that the localized GFRAL silencing by shRNA in the area postrema/nucleus tractus solitarius of hSOD1^G93A mice induces weight gain, reduces adipose tissue wasting, ameliorates the motor function and muscle atrophy and prolongs the survival time. We report that microglial cells could be involved in mediating these effects because their depletion with PLX5622 reduces brainstem GDF15 expression, weight loss and the expression of lipolytic genes in adipose tissue. Altogether these results reveal a key role of GDF15-GFRAL signaling in regulating weight loss and the alteration of and lipid metabolism in the early phases of ALS.