The effect of pH alterations on TDP-43 in a cellular model of amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons. The pathophysiology of ALS is not well understood but TDP-43 proteinopathy (aggregation and mislocalization) is one of the major phenomena described. Several factors can influence TDP-43 behavior such as mild pH alterations that can induce conformational changes in recombinant TDP-43, increasing its propensity to aggregate. However to our knowledge, no studies have been conducted yet in a cellular setting, in the context of ALS. We therefore tested the effect of cellular pH alterations on the localization, aggregation, and phosphorylation of TDP-43. HEK293T cells overexpressing wildtype TDP-43 were incubated for 1 h with solutions of different pH (6.4, 7.2, and 8). Incubation of cells for 1 h in solutions of pH 6.4 and 8 led to an increase in TDP-43-positive puncta. This was accompanied by the mislocalization of TDP-43 from the nucleus to the cytoplasm. Our results suggest that small alterations in cellular pH affect TDP-43 and increase its mislocalization into cytoplasmic TDP-43-positive puncta, which might suggest a role of TDP-43 in the response of cells to pH alterations.

Taking Advantages of Blood-Brain or Spinal Cord Barrier Alterations or Restoring Them to Optimize Therapy in ALS?

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that still lacks an efficient therapy. The barriers between the central nervous system (CNS) and the blood represent a major limiting factor to the development of drugs for CNS diseases, including ALS. Alterations of the blood-brain barrier (BBB) or blood-spinal cord barrier (BSCB) have been reported in this disease but still require further investigations. Interestingly, these alterations might be involved in the complex etiology and pathogenesis of ALS. Moreover, they can have potential consequences on the diffusion of candidate drugs across the brain. The development of techniques to bypass these barriers is continuously evolving and might open the door for personalized medical approaches. Therefore, identifying robust and non-invasive markers of BBB and BSCB alterations can help distinguish different subgroups of patients, such as those in whom barrier disruption can negatively affect the delivery of drugs to their CNS targets. The restoration of CNS barriers using innovative therapies could consequently present the advantage of both alleviating the disease progression and optimizing the safety and efficiency of ALS-specific therapies.

Hypoxia-induced carbonic anhydrase mediated dorsal horn neuron activation and induction of neuropathic pain.

ABSTRACT: Neuropathic pain, such as that seen in diabetes mellitus, results in part from central sensitisation in the dorsal horn. However, the mechanisms responsible for such sensitisation remain unclear. There is evidence that disturbances in the integrity of the spinal vascular network can be causative factors in the development of neuropathic pain. Here we show that reduced blood flow and vascularity of the dorsal horn leads to the onset of neuropathic pain. Using rodent models (type 1 diabetes and an inducible endothelial-specific vascular endothelial growth factor receptor 2 knockout mouse) that result in degeneration of the endothelium in the dorsal horn, we show that spinal cord vasculopathy results in nociceptive behavioural hypersensitivity. This also results in increased hypoxia in dorsal horn neurons, depicted by increased expression of hypoxia markers such as hypoxia inducible factor 1α, glucose transporter 3, and carbonic anhydrase 7. Furthermore, inducing hypoxia through intrathecal delivery of dimethyloxalylglycine leads to the activation of dorsal horn neurons as well as mechanical and thermal hypersensitivity. This shows that hypoxic signalling induced by reduced vascularity results in increased hypersensitivity and pain. Inhibition of carbonic anhydrase activity, through intraperitoneal injection of acetazolamide, inhibited hypoxia-induced pain behaviours. This investigation demonstrates that induction of a hypoxic microenvironment in the dorsal horn, as occurs in diabetes, is an integral process by which neurons are activated to initiate neuropathic pain states. This leads to the conjecture that reversing hypoxia by improving spinal cord microvascular blood flow could reverse or prevent neuropathic pain.

Therapeutic antibodies - natural and pathological barriers and strategies to overcome them.

Antibody-based therapeutics have become a major class of therapeutics with over 120 recombinant antibodies approved or under review in the EU or US. This therapeutic class has experienced a remarkable expansion with an expected acceleration in 2021-2022 due to the extraordinary global response to SARS-CoV2 pandemic and the public disclosure of over a hundred anti-SARS-CoV2 antibodies. Mainly delivered intravenously, alternative delivery routes have emerged to improve antibody therapeutic index and patient comfort. A major hurdle for antibody delivery and efficacy as well as the development of alternative administration routes, is to understand the different natural and pathological barriers that antibodies face as soon as they enter the body up to the moment they bind to their target antigen. In this review, we discuss the well-known and more under-investigated extracellular and cellular barriers faced by antibodies. We also discuss some of the strategies developed in the recent years to overcome these barriers and increase antibody delivery to its site of action. A better understanding of the biological barriers that antibodies have to face will allow the optimization of antibody delivery near its target. This opens the way to the development of improved therapy with less systemic side effects and increased patients' adherence to the treatment.

Mitochondrial bioenergetics, uncoupling protein-2 activity, and reactive oxygen species production in the small intestine of a TNBS-induced colitis rat model.

Inflammatory bowel disease (IBD) is often associated with a decrease in energy-dependent nutrient uptake across the jejunum that serves as the main site for absorption in the small intestine. This association has prompted us to investigate the bioenergetics underlying the alterations in jejunal absorption in 2,4,6-trinitrobenzenesulfonic acid-induced colitis in rats. We have found that mitochondrial oxygen consumption did not change in state 2 and state 3 respirations but showed an increase in state 4 respiration indicating a decrease in the respiratory control ratio of jejunal mitochondria during the peak of inflammation. This decrease in the coupling state was found to be guanosine diphosphate-sensitive, hence, implicating the involvement of uncoupling protein-2 (UCP2). Furthermore, the study has reported that the production of reactive oxygen species (ROS), known to be activators of UCP2, correlated negatively with UCP2 activity. Thus, we suggest that ROS production in the jejunum might be activating UCP2 which has an antioxidant activity, and that uncoupling of the mitochondria decreases the efficiency of energy production, leading to a decrease in energy-dependent nutrient absorption. Hence, this study is the first to account for an involvement of energy production and a role for UCP2 in the absorptive abnormalities of the small intestine in animal models of colitis.