Local Administration of Minocycline Improves Nerve Regeneration in Two Rat Nerve Injury Models

Peripheral nerve injuries are quite common and often require a surgical intervention. However, even after surgery, patients do not often regain satisfactory sensory and motor functions. This, in turn, results in a heavy socioeconomic burden. To some extent, neurons can regenerate from the proximal nerve stump and try to reconnect to the distal stump. However, this regenerating capacity is limited, and depending on the type and size of peripheral nerve injury, this process may not lead to a positive outcome. To date, no pharmacological approach has been used to improve nerve regeneration following repair surgery. We elected to investigate the effects of local delivery of minocycline on nerve regeneration. This molecule has been studied in the central nervous system and was shown to improve the outcome in many disease models. In this study, we first tested the effects of minocycline on SCL 4.1/F7 Schwann cells in vitro and on sciatic nerve explants. We specifically focused on the Schwann cell repair phenotype, as these cells play a central role in orchestrating nerve regeneration. Finally, we delivered minocycline locally in two different rat models of nerve injury, a sciatic nerve transection and a sciatic nerve autograft, demonstrating the capacity of local minocycline treatment to improve nerve regeneration

Electrospun aligned tacrolimus-loaded polycaprolactone biomaterials for peripheral nerve repair

Background: Efficacious repair of peripheral nerve injury is an unmet clinical need. The implantation of biomaterials containing neurotrophic drugs at the injury site could promote nerve regeneration and improve outcomes for patients. Materials & methods: Random and aligned electrospun poly-ε-caprolactone scaffolds containing encapsulated tacrolimus were fabricated, and the gene expression profile of Schwann cells (SCs) cultured on the surface was elucidated. On aligned fibers, the morphology of SCs and primary rat neurons was investigated. Results: Both scaffold types exhibited sustained release of drug, and the gene expression of SCs was modulated by both nanofibrous topography and the presence of tacrolimus. Aligned fibers promoted the alignment of SCs and orientated outgrowth from neurons. Conclusion: Electrospun PCL scaffolds with tacrolimus hold promise for the repair of peripheral nerve injury

Exploring the Nerve Regenerative Capacity of Compounds with Differing Affinity for PPARγ In Vitro and In Vivo

Damage to peripheral nerves can cause debilitating consequences for patients such as lifelong pain and disability. At present, no drug treatments are routinely given in the clinic following a peripheral nerve injury (PNI) to improve regeneration and remyelination of damaged nerves. Appropriately targeted therapeutic agents have the potential to be used at different stages following nerve damage, e.g., to maintain Schwann cell viability, induce and sustain a repair phenotype to support axonal growth, or promote remyelination. The development of therapies to promote nerve regeneration is currently of high interest to researchers, however, translation to the clinic of drug therapies for PNI is still lacking. Studying the effect of PPARγ agonists for treatment of peripheral nerve injures has demonstrated significant benefits. Ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), has reproducibly demonstrated benefits in vitro and in vivo, suggested to be due to its agonist action on PPARγ. Other NSAIDs have demonstrated differing levels of PPARγ activation based upon their affinity. Therefore, it was of interest to determine whether affinity for PPARγ of selected drugs corresponded to an increase in regeneration. A 3D co-culture in vitro model identified some correlation between these two properties. However, when the drug treatments were screened in vivo, in a crush injury model in a rat sciatic nerve, the same correlation was not apparent. Further differences were observed between capacity to increase axon number and improvement in functional recovery. Despite there not being a clear correlation between affinity and size of effect on regeneration, all selected PPARγ agonists improved regeneration, providing a panel of compounds that could be explored for use in the treatment of PNI

Development of ibuprofen-loaded electrospun materials suitable for surgical implantation in peripheral nerve injury

The development of nerve wraps for use in the repair of peripheral nerves has shown promise over recent years. A pharmacological effect to improve regeneration may be achieved by loading such materials with therapeutic agents, for example ibuprofen, a non-steroidal anti-inflammatory drug with neuroregenerative properties. In this study, four commercially available polymers (polylactic acid (PLA), polycaprolactone (PCL) and two co-polymers containing different ratios of PLA to PCL) were used to fabricate ibuprofen-loaded nerve wraps using blend electrospinning. In vitro surgical handling experiments identified a formulation containing a PLA/PCL 70/30 molar ratio co-polymer as the most suitable for in vivo implantation. In a rat model, ibuprofen released from electrospun materials significantly improved the rate of axonal growth and sensory recovery over a 21-day recovery period following a sciatic nerve crush. Furthermore, RT-qPCR analysis of nerve segments revealed that the anti-inflammatory and neurotrophic effects of ibuprofen may still be observed 21 days after implantation. This suggests that the formulation developed in this work could have potential to improve nerve regeneration in vivo

A quantitative LC-MS/MS method for analysis of mitochondrial -specific oxysterol metabolism

Oxysterols are critical regulators of inflammation and cholesterol metabolism in cells. They are oxidation products of cholesterol and may be differentially metabolised in subcellular compartments and in biological fluids. New analytical methods are needed to improve our understanding of oxysterol trafficking and the molecular interplay between the cellular compartments required to maintain cholesterol/oxysterol homeostasis. Here we describe a method for isolation of oxysterols using solid phase extraction and quantification by liquid chromatography-mass spectrometry, applied to tissue, cells and mitochondria. We analysed five monohydroxysterols; 24(S)-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, 7α-hydroxycholesterol, 7 ketocholesterol and three dihydroxysterols 7α-24(S)dihydroxycholesterol, 7α-25dihydroxycholesterol, 7α-27dihydroxycholesterol by LC-MS/MS following reverse phase chromatography. Our new method, using Triton and DMSO extraction, shows improved extraction efficiency and recovery of oxysterols from cellular matrix. We validated our method by reproducibly measuring oxysterols in mouse brain tissue and showed that mice fed a high fat diet had significantly lower levels of 24S/25diOHC, 27diOHC and 7ketoOHC. We measured oxysterols in mitochondria from peripheral blood mononuclear cells and highlight the importance of rapid cell isolation to minimise effects of handling and storage conditions on oxysterol composition in clinical samples. In addition, in vitro cell culture systems, of THP-1 monocytes and neuronal-like SH-SH5Y cells, showed mitochondrial-specific oxysterol metabolism and profiles were lineage specific. In summary, we describe a robust and reproducible method validated for improved recovery, quantitative linearity and detection, reproducibility and selectivity for cellular oxysterol analysis. This method enables subcellular oxysterol metabolism to be monitored and is versatile in its application to various biological and clinical samples

CNS targets of adipokines

This is the author accepted manuscript. The final version is available from American Physiological Society via the DOI in this record.Our understanding of adipose tissue as an endocrine organ has been transformed over the last twenty years. During this time a number of adipocyte-derived factors or adipokines have been identified. This paper will review evidence for how adipokines acting via the central nervous system (CNS) regulate normal physiology and disease pathology. The reported CNS-mediated effects of adipokines are varied and include the regulation of energy homeostasis, autonomic nervous system activity, the reproductive axis, neurodevelopment, cardiovascular function, and cognition. Due to the wealth of information available and the diversity of their known functions, the archetypal adipokines leptin and adiponectin will be the focused on extensively. Other adipokines with established CNS actions will also be discussed. Due to the difficulties associated with studying CNS function on a molecular level in humans, the majority of our knowledge, and as such the studies described in this paper, comes from work in experimental animal models; however, where possible the relevant data from human studies are also highlighted

Health relevance of the modification of low grade inflammation in ageing (inflammageing) and the role of nutrition

Ageing of the global population has become a public health concern with an important socio-economic dimension. Ageing is characterized by an increase in the concentration of inflammatory markers in the bloodstream, a phenomenon that has been termed "inflammageing". The inflammatory response is beneficial as an acute, transient reaction to harmful conditions, facilitating the defense, repair, turnover and adaptation of many tissues. However, chronic and low grade inflammation is likely to be detrimental for many tissues and for normal functions. We provide an overview of low grade inflammation (LGI) and determine the potential drivers and the effects of the "inflamed" phenotype observed in the elderly. We discuss the role of gut microbiota and immune system crosstalk and the gut-brain axis. Then, we focus on major health complications associated with LGI in the elderly, including mental health and wellbeing, metabolic abnormalities and infections. Finally, we discuss the possibility of manipulating LGI in the elderly by nutritional interventions. We provide an overview of the evidence that exists in the elderly for omega-3 fatty acid, probiotic, prebiotic, antioxidant and polyphenol interventions as a means to influence LGI. We conclude that slowing, controlling or reversing LGI is likely to be an important way to prevent, or reduce the severity of, age-related functional decline and the onset of conditions affecting health and well-being; that there is evidence to support specific dietary interventions as a strategy to control LGI; and that a continued research focus on this field is warranted

Central nervous system inflammation in the context of obesity : implication of bioactive lipids and pathophysiological repercussions

Obesity and sedentary lifestyle are on the rise and pose serious threats to people's health. Indeed, obesity is associated with a cluster of comorbidities collectively known as the metabolic syndrome and represents one of the most alarming health issues of modern times. Amongst other etiologies, a high-fat diet and cholesterol metabolism are key players in the genesis of these disorders and lead to the onset of a low-grade inflammation affecting both the periphery and the central nervous system. In this context, obesity can be considered as an inflammatory condition. We are particularly interested in the consequences of obesity on neuroinflammation and in the involvement of bioactive lipids in these processes. We first wanted to study the impact of obesity and subsequent low grade inflammation on different structures of the central nervous system. We found that the inflammatory tone during diet-induced obesity was both time-dependent and structure-dependent with, for instance, striking differences between the cerebellum (increased inflammatory markers’ expression and astrocyte activation) and the cortex (no changes) when compared after 16 weeks of high fat diet. We further interrogated the potential involvement of bioactive lipids in these inflammatory differences. We singled out four lipid families and one species as potentially exerting anti-inflammatory effects and upon ex-vivo testing on co-culture of primary astrocytes and microglia, we identified phosphatidyinositols, lysophosphatidylcholine and palmitoylethanolamide as able to decrease inflammatory markers’ expression. In another study, instead of assessing different families of bioactive lipids in the context of diet-induced inflammation, we focused on one specific family, namely the oxysterols. First, using different models of obesity, either from genetic origins or diet-induced, we measured oxysterol levels in tissues affected by the subsequent obesity-induced inflammation. We also assessed the expression of metabolic enzymes responsible for oxysterols’ synthesis and degradation. Interestingly, based on the hepatic levels of three oxysterol levels (4β-hydroxycholesterol, 27-hydroxycholesterol, and 7-hydroxycholestenone) and their hepatic synthesis enzymes’ expression (CYP3a11, CYP27a1, and CYP7a1) we were able to discriminate between a lean and an obese phenotype regardless of the experimental model used. Finally, another important finding of this study was the sustained and significant decrease of 4β-hydroxycholesterol levels, as soon as after one week of high-fat diet and until sixteen weeks, in the liver, adipose tissue, and plasma as well as decreased levels in the hypothalamus from six weeks on. Finally, we wondered what would be the potential impact of another inflammatory insult in the context of obesity. We chose to use a post-operative pain model, the hind paw incision, and devised three separate studies. The first one allowed us to identify diet-induced obesity as able to significantly increase post-operative pain. The second study enabled us to identify some mechanisms potentially explaining this prolonged pain. Indeed, the sciatic nerve inflammatory tone and more specifically macrophage recruitment and activation, glial cells activation in the dorsal horn of the spinal cord and an increased endoplasmic reticulum stress represent different mechanisms that could explain the obesity-induced prolonged post-operative pain. Finally, in an interventional study, we used a diet switch from a high-fat diet to a standard show. This dietary intervention was able to rescue the prolonged pain. We also measured bioactive lipid levels in the paw, the sciatic nerve, and the spinal cord of these animals but unfortunately we could not identify lipids potentially linked to the obesity-induced prolonged post-operative pain. This work allowed for a better comprehension of the impact of obesity on the central nervous system by nuancing it according to the different effects observed in specific structures. It also evaluated the implication of bioactive lipids involvement in the context of obesity-induced inflammation some of which were never quantified in these conditions before. Finally, we interrogated some pathophysiological implications in the context of obesity using a post-operative pain model and we demonstrated that obesity significantly prolonged post-operative pain. Taken together, this work paves the way for further studies addressing the link between bioactive lipids involvement in the context of obesity-induced inflammation and neuroinflammation.(BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 201

Oxysterols: From cholesterol metabolites to key mediators

Oxysterols are cholesterol metabolites that can be produced through enzymatic or radical processes. They constitute a large family of lipids (i.e. the oxysterome) involved in a plethora of physiological processes. They can act through GPCR (e.g. EBI2, SMO, CXCR2), nuclear receptors (LXR, ROR, ERα) and through transporters or regulatory proteins. Their physiological effects encompass cholesterol, lipid and glucose homeostasis. Additionally, they were shown to be involved in other processes such as immune regulatory functions and brain homeostasis. First studied as precursors of bile acids, they quickly emerged as interesting lipid mediators. Their levels are greatly altered in several pathologies and some oxysterols (e.g. 4β-hydroxycholesterol or 7α-hydroxycholestenone) are used as biomarkers of specific pathologies. In this review, we discuss the complex metabolism and molecular targets (including binding properties) of these bioactive lipids in human and mice. We also discuss the genetic mouse models currently available to interrogate their effects in pathophysiological settings. We also summarize the levels of oxysterols reported in two key organs in oxysterol metabolism (liver and brain), plasma and cerebrospinal fluid. Finally, we consider future opportunities and directions in the oxysterol field in order to gain a better insight and understanding of the complex oxysterol syste