Neurotrauma and inflammation: CNS and PNS responses.

Traumatic injury to the central nervous system (CNS) or the peripheral nervous system (PNS) triggers a cascade of events which culminate in a robust inflammatory reaction. The role played by inflammation in the course of degeneration and regeneration is not completely elucidated. While, in peripheral nerves, the inflammatory response is assumed to be essential for normal progression of Wallerian degeneration and regeneration, CNS trauma inflammation is often associated with poor recovery. In this review, we discuss key mechanisms that trigger the inflammatory reaction after nervous system trauma, emphasizing how inflammations in both CNS and PNS differ from each other, in terms of magnitude, cell types involved, and effector molecules. Knowledge of the precise mechanisms that elicit and maintain inflammation after CNS and PNS tissue trauma and their effect on axon degeneration and regeneration is crucial for the identification of possible pharmacological drugs that can positively affect the tissue regenerative capacity.

Neutrophil-mediated hypoxia drives pathogenic CD8 T cell responses in cutaneous leishmaniasis.

Cutaneous leishmaniasis caused by Leishmania parasites exhibits a wide range of clinical manifestations. Although parasites influence disease severity, cytolytic CD8 T cell responses mediate disease. While these responses originate in the lymph node, we found that expression of the cytolytic effector molecule granzyme B was restricted to lesional CD8 T cells in Leishmania-infected mice, suggesting that local cues within inflamed skin induced cytolytic function. Expression of Blimp-1 (Prdm1), a transcription factor necessary for cytolytic CD8 T cell differentiation, was driven by hypoxia within the inflamed skin. Hypoxia was further enhanced by the recruitment of neutrophils that consumed oxygen to produce reactive oxygen species and ultimately increased the hypoxic state and granzyme B expression in CD8 T cells. Importantly, lesions from cutaneous leishmaniasis patients exhibited hypoxia transcription signatures that correlated with the presence of neutrophils. Thus, targeting hypoxia-driven signals that support local differentiation of cytolytic CD8 T cells may improve the prognosis for patients with cutaneous leishmaniasis, as well as other inflammatory skin diseases where cytolytic CD8 T cells contribute to pathogenesis.

Pathogenic CD8 T cell responses are driven by neutrophil-mediated hypoxia in cutaneous leishmaniasis.

Cutaneous leishmaniasis caused by Leishmania parasites exhibits a wide range of clinical manifestations. Although parasites influence disease severity, cytolytic CD8 T cell responses mediate disease. While these responses originate in the lymph node, we find that expression of the cytolytic effector molecule granzyme B is restricted to lesional CD8 T cells in Leishmania - infected mice, suggesting that local cues within inflamed skin induce cytolytic function. Expression of Blimp-1 ( Prdm1 ), a transcription factor necessary for cytolytic CD8 T cell differentiation, is driven by hypoxia within the inflamed skin. Hypoxia is further enhanced by the recruitment of neutrophils that consume oxygen to produce reactive oxygen species, ultimately increasing granzyme B expression in CD8 T cells. Importantly, lesions from cutaneous leishmaniasis patients exhibit hypoxia transcription signatures that correlate with the presence of neutrophils. Thus, targeting hypoxia-driven signals that support local differentiation of cytolytic CD8 T cells may improve the prognosis for patients with cutaneous leishmaniasis, as well as other inflammatory skin diseases where cytolytic CD8 T cells contribute to pathogenesis.

Immunoelectron microscopy reveals the presence of neurofilament proteins in retinal terminals undergoing dark degeneration.

After nerve crushing or section, the distal stump undergoes morphological changes described as Wallerian degeneration (WD). Immediately after nerve injury, early ultrastructural alterations occur in the terminal boutons, a process known as terminal degeneration (TD), which occurs before degeneration of the axon and leads to electrophysiological impairment. In this study we investigated the presence of neurofilament (NF) proteins in TD and compared the results with degeneration in the optic nerve. Young adult Wistar rats were submitted to bilateral enucleation and perfused after 24 h, 48 h and 1 week. Optic nerves (ON) and superior colliculus (SC) segments were processed for electron microscopy (EM) and immunoelectron microscopy (IEM) for NF subunits. Analysis of ultrathin sections of SC, at 24 h, revealed terminals undergoing TD. At 48 h and 1 week after enucleation, there was a clear increase in the number of degenerating terminals. The cytoarchitecture of the optic nerve did not change considerably at 24 h, but it was progressively altered at 48 h and 1 week after enucleation, when we observed intense astrogliosis, and most fibers exhibited dark degeneration (DD). The IEM for the NF subunits of normal ON showed gold particles located along the filaments, but we did not observe labeling for neurofilament proteins in normal retinal terminals. However, 48 h after lesion, we observed immunogold particles for the NF proteins in fibers undergoing DD and on terminals undergoing TD. Therefore, we can conclude that NF proteins participate in the process of TD, and this event occurs before complete axonal degeneration, suggesting different mechanisms for TD and DD.

Gut Microbiota Are Disease-Modifying Factors After Traumatic Spinal Cord Injury.

Spinal cord injury (SCI) disrupts the autonomic nervous system (ANS), impairing its ability to coordinate organ function throughout the body. Emerging data indicate that the systemic pathology that manifests from ANS dysfunction exacerbates intraspinal pathology and neurological impairment. Precisely how this happens is unknown, although new data, in both humans and in rodent models, implicate changes in the composition of bacteria in the gut (i.e., the gut microbiota) as disease-modifying factors that are capable of affecting systemic physiology and pathophysiology. Recent data from rodents indicate that SCI causes gut dysbiosis, which exacerbates intraspinal inflammation and lesion pathology leading to impaired recovery of motor function. Postinjury delivery of probiotics containing various types of "good" bacteria can partially overcome the pathophysiologal effects of gut dysbiosis; immune function, locomotor recovery, and spinal cord integrity are partially restored by a sustained regimen of oral probiotics. More research is needed to determine whether gut dysbiosis varies across a range of clinically relevant variables, including sex, injury level, and injury severity, and whether changes in the gut microbiota can predict the onset or severity of common postinjury comorbidities, including infection, anemia, metabolic syndrome, and, perhaps, secondary neurological deterioration. Those microbial populations that dominate the gut could become "druggable" targets that could be manipulated via dietary interventions. For example, personalized nutraceuticals (e.g., pre- or probiotics) could be developed to treat the above comorbidities and improve health and quality of life after SCI.

Lack of galectin-3 improves the functional outcome and tissue sparing by modulating inflammatory response after a compressive spinal cord injury.

Spinal cord injury (SCI) is a traumatic event that results in motor, sensitive or autonomic function disturbances, which have direct impact on the life quality of the affected individual. Recent studies have shown that attenuation of the inflammatory response after SCI plays a key role in the reestablishment of motor function. Galectin-3 is a pleiotropic molecule belonging to the carbohydrate-ligand lectin family, which is expressed by different cells in different tissues. Studies have shown that galectin-3 induces the recruitment and activation of neutrophils, monocytes/macrophages, lymphocytes and microglia. Thus, the aim of this study was to evaluate the effects of the lack of galectin-3 on the functional outcome, cellular recruitment and morphological changes in tissue, after SCI. C57BL/6 wild-type and galectin-3 knockout mice were used in this study. A vascular clip was used for 1 min to generate a compressive SCI. By BMS we detected that the Gal-3(-/-) presented a better functional outcome during the studied period. This finding is related to a decrease in the injury length and a higher volume of spared white matter at 7 and 42 days post injury (dpi). Moreover, Gal-3(-/-) mice showed a higher number of spared fibers at 28 dpi. Because of the importance of the inflammatory response after SCI and the role that galectin-3 plays in it, we investigated possible differences in the inflammatory response between the analyzed groups. No differences in neutrophils were observed 24h after injury. However, at 3 dpi, the Gal-3(-/-) mice showed more neutrophils infiltrated into the spinal tissue when compared with the WT mice. At this same time point, no differences in the percentage of the CD11b/Arginase1 positive cells were observed. Remarkably, Gal-3(-/-) mice displayed a decrease in CD11b staining at 7 dpi, compared with the WT mice. At the same time, Gal-3(-/-) mice presented a more prominent Arginase1 stained area, suggesting an anti-inflammatory cell phenotype. Taken together, these results demonstrated that the lack of galectin-3 plays a key role in the inflammatory process triggered by SCI, leading to better and early recovery of locomotor function.

A highly reproducible mouse model of compression spinal cord injury.

Experimental spinal cord injury (SCI) can maintain the continuity of the spinal cord, as in the contusion (e.g., weight-fall) or compression models, or not, when there is a partial or a complete transection. The majority of acute human SCI is not followed by complete transection, but there is a combination of contusion, compression, and possibly partial transection. The method described here is a compressive mouse model that presents a combination of contusion and compression components and has many facilities in its execution. This lesion was established by our group and represents a simple, reliable, and inexpensive clip compression model with functional and morphological reproducibility. In this chapter we describe, step by step, the protocol of this experimental SCI.

Bone marrow mesenchymal stem cell transplantation for improving nerve regeneration.

Although the peripheral nervous system has an inherent capacity for regeneration, injuries to nerves still result in considerable disabilities. The persistence of these disabilities along with the underlying problem of nerve reconstruction has motivated neuroscientists worldwide to seek additional therapeutic strategies. In recent years, cell-based therapy has emerged as a promising therapeutic tool. Schwann cells (SCs) are the main supportive cells for peripheral nerve regeneration; however, there are several technical limitations regarding its application for cell-based therapy. In this context, bone marrow mesenchymal stem cells (BM-MSCs) have been used as alternatives to SCs for treating peripheral neuropathies, showing great promise. Several studies have been trying to shed light on the mechanisms behind the nerve regeneration-promotion potential of BM-MSCs. Although not completely clarified, understanding how BM-MSCs exert tissue repair effects will facilitate their development as therapeutic agents before they become a clinically viable tool for encouraging peripheral nerve regeneration.