Who let the dogs out?: detrimental role of Galectin-3 in hypoperfusion-induced retinal degeneration

The Role of Galectin-3 in Retinal Degeneration and Other Ocular Diseases: A Potential Novel Biomarker and Therapeutic Target

Galectin-3 is the most studied member of the Galectin family, with a large range of mediation in biological activities such as cell growth, proliferation, apoptosis, differentiation, cell adhesion, and tissue repair, as well as in pathological processes such as inflammation, tissue fibrosis, and angiogenesis. As is known to all, inflammation, aberrant cell apoptosis, and neovascularization are the main pathophysiological processes in retinal degeneration and many ocular diseases. Therefore, the review aims to conclude the role of Gal3 in the retinal degeneration of various diseases as well as the occurrence and development of the diseases and discuss its molecular mechanisms according to research in systemic diseases. At the same time, we summarized the predictive role of Gal3 as a biomarker and the clinical application of its inhibitors to discuss the possibility of Gal3 as a novel target for the treatment of ocular diseases.

The interaction between intestinal microenvironment and stroke

BACKGROUND

Stroke is not only a major cause of disability but also the third leading cause of death, following heart disease and cancer. It has been established that stroke causes permanent disability in 80% of survivors. However, current treatment options for this patient population are limited. Inflammation and immune response are major features that are well-recognized to occur after a stroke. The gastrointestinal tract hosts complex microbial communities, the largest pool of immune cells, and forms a bidirectional regulation brain-gut axis with the brain. Recent experimental and clinical studies have highlighted the importance of the relationship between the intestinal microenvironment and stroke. Over the years, the influence of the intestine on stroke has emerged as an important and dynamic research direction in biology and medicine.

AIMS

In this review, we describe the structure and function of the intestinal microenvironment and highlight its cross-talk relationship with stroke. In addition, we discuss potential strategies aiming to target the intestinal microenvironment during stroke treatment.

CONCLUSION

The structure and function of the intestinal environment can influence neurological function and cerebral ischemic outcome. Improving the intestinal microenvironment by targeting the gut microbiota may be a new direction in treating stroke.

Effects of galectin-3 protein on UVA-induced damage in retinal pigment epithelial cells

Several inflammatory molecules have been suggested as biomarkers of age-related macular degeneration (AMD). Galectin-3 (Gal-3), which has been shown to have a protective role in corneal injury by promoting epithelial cells adhesion and migration to the extracellular matrix, is also highly expressed in the retinal pigment epithelium (RPE) of patients with AMD. This study evaluated the role of Gal-3 in an in vitro model of UVA-induced RPE damage, as a proof-of-concept. ARPE-19 cells (human RPE cell line), were incubated with Gal-3 at 0.5-2.5 µg/mL concentrations prior to UVA irradiation for 15, 30, and 45 min, which resulted in accumulated doses of 2.5, 5, and 7.5 J/cm², respectively. After 24 h incubation, MTT and LDH assays, immunofluorescence, and ELISA were performed. UVA irradiation for 15, 30, and 45 min proved to reduce viability in 83%, 46%, and 11%, respectively. Based on the latter results, we chose the intermediate dose (5-J/cm²) for further analysis. Pretreatment with Gal-3 at concentrations > 1.5 µg/mL showed to increase the viability of UVA-irradiated cells (~ 75%) compared to untreated cells (64%). Increased levels of cleaved caspase 3, a marker of cell death, were detected in the ARPE cells after UVA irradiation with or without addition of exogenous Gal-3. The inhibitory effect of Gal-3 on UVA-induced cell damage was characterized by decreased ROS levels and increased p38 activation, as detected by fluorescence analysis. In conclusion, our study suggests a photoprotective effect of Gal-3 on RPE by reducing oxidative stress and increasing p38 activation.

Galectin-3 protects auditory function in female mice

Sex differences in the development of sensorineural hearing loss have been recognized in various inner ear disorders, but the molecular basis for such differences is poorly understood. Autosomal genes have been shown to cause sex differences in disease susceptibility, but many genes exerting sex-dependent effects on auditory function remain to be identified. Galectin-3 (Gal-3), a protein encoded by the autosomal gene Lgals3, is a member of the β-galactoside-binding protein family, and has been linked to multiple biological processes, including immune responses, apoptosis, and cell adhesion. Here, we investigated auditory function and hair cell integrity in Gal-3 knockout (KO, Lgals3^-/-) and wild-type (WT, Lgals3^+/+) mice from age 1 to 6 months. KO mice show a more rapid age-related increase in ABR thresholds compared to WT mice. Noticeably, the threshold deterioration in female KO mice is significantly greater than in the male KO and WT mice. The ABR threshold elevation manifests over a broad frequency range in female KO mice, whereas the threshold elevations are confined to high frequencies in the male KO and WT mice. Moreover, DPOAE input/output functions reveal a similar pattern of auditory dysfunction, with the female KO mice displaying a significantly greater reduction in DPOAE amplitudes than male KO mice and WT mice of both sexes. Finally, age-related outer hair cell loss is greater for female KO mice compared to male KO mice and WT mice of both sexes. Together, these results indicate that Gal-3 deficiency exacerbates age-related cochlear degeneration and auditory dysfunction in female mice. Our study identifies Gal-3 as a sex-dependent molecule for maintaining female cochlear integrity.

Regulating microglial miR-155 transcriptional phenotype alleviates Alzheimer's-induced retinal vasculopathy by limiting Clec7a/Galectin-3+ neurodegenerative microglia

Single cell RNA sequencing studies identified novel neurodegeneration-associated microglial (MGnD/DAM) subtypes activated around cerebral amyloid plaques. Micro-RNA (miR)-155 of the TREM2-APOE pathway was shown to be a key transcriptional regulator of MGnD microglial phenotype. Despite growing interest in studying manifestations of Alzheimer's disease (AD) in the retina, a CNS organ accessible to noninvasive high-resolution imaging, to date MGnD microglia have not been studied in the AD retina. Here, we discovered the presence and increased populations of Clec7a+ and Galectin-3+ MGnD microglia in retinas of transgenic APPSWE/PS1L166P AD-model mice. Conditionally targeting MGnD microglia by miR-155 ablation via the tamoxifen-inducible CreERT2 system in APPSWE/PS1L166P mice diminished retinal Clec7a+ and Galectin-3+ microglial populations while increasing homeostatic P2ry12+ microglia. Retinal MGnD microglia were often adhering to microvessels; their depletion protected the inner blood-retina barrier and reduced vascular amyloidosis. Microglial miR-155 depletion further limits retinal inflammation. Mass spectrometry analysis revealed enhanced retinal PI3K-Akt signaling and predicted IL-8 and Spp1 decreases in mice with microglia-specific miR-155 knockout. Overall, this study identified MGnD microglia in APPSWE/PS1L166P mouse retina. Transcriptional regulation of these dysfunctional microglia mitigated retinal inflammation and vasculopathy. The protective effects of microglial miR-155 ablation should shed light on potential treatments for retinal inflammation and vascular damage during AD and other ocular diseases.

Galectin-3 ablation does not affect infarct size or inflammatory cytokines after experimental stroke in 24-month-old female mice

BACKGROUND

The tissue damage following a focal stroke causes an inflammatory response that is thought to aggravate the disease state. Galectin-3 is a proinflammatory molecule that has been shown to play a significant role in the inflammatory responses in brain diseases and following experimental stroke. In most animal experiments, young animals are used, although attempts are often made to model diseases that affect the elderly. Therefore, in this project, we intended to investigate the role of Galectin-3 in experimental stroke in older mice.

METHODS

In this project, 24-month-old (aged) female mice were subjected to an experimental stroke (permanent middle cerebral artery occlusion) 7 days before sacrifice. We wanted to investigate whether the absence of the inflammatory protein Galectin-3 could affect motor phenotype, neuroinflammation and infarct size. Number of mice without Galectin-3 (Galectin-3 KO) = 9, number of wildtype controls of the same age = 6.

RESULTS

In our aged female mice, we could not observe any significant differences between Galectin-3 KO and wildtype regarding the inclined plane test or cylinder test. We could not observe different infarct sizes between the two genotypes. In brain homogenates, we measured levels of 10 inflammatory cytokines, but we could not see any significant differences in any of them.

CONCLUSION

In summary, it can be said that the absence of the inflammatory mediator Galectin-3 does not seem to have a strong poststroke effect in aged females. Unfortunately, we could not analyze these mice with immunohistochemistry, which limited our study.

Long-Term Connectome Analysis Reveals Reshaping of Visual, Spatial Networks in a Model With Vascular Dementia Features

Connectome analysis of neuroimaging data is a rapidly expanding field that offers the potential to diagnose, characterize, and predict neurological disease. Animal models provide insight into biological mechanisms that underpin disease, but connectivity approaches are currently lagging in the rodent.

Galectins - Important players of the immune response to CNS parasitic infection

Galectins are a family of proteins that bind β-galactosides and play key roles in a variety of cellular processes including host defense and entry of parasites into the host cells. They have been well studied in hosts but less so in parasites. As both host and parasite galectins are highly upregulated proteins following infection, galectins are an area of increasing interest and their role in immune modulation has only recently become clear. Correlation of CNS parasitic diseases with mental disorders as a result of direct or indirect interaction has been observed. Therefore, galectins produced by the parasite should be taken into consideration as potential therapeutic agents.

Microglia-derived galectin-3 in neuroinflammation; a bittersweet ligand?

Galectins are soluble β-galactoside-binding proteins found in all multicellular organisms. Galectins may act as danger-associated molecular patterns in innate immunity and/or as pattern-recognition receptors that bind to pathogen-associated molecular patterns. Among different galectin family members, galectin-3 has been the focus of studies in neurodegenerative diseases in recent years. This lectin modulates brain innate immune responses, microglia activation patterns in physiological and pathophysiological settings in a context-dependent manner. Galectin-3 is considered as a pivotal tuner of macrophage and microglial activity. Indeed galectin-3 acts as a double edged sword in neuroinflammatory context and this multimodal lectin has diverse roles in physiological and pathophysiological conditions. Better understanding of galectin-3 physiology (its extracellular and intracellular actions) and structure (its C terminus vs. N terminus) is instrumental to design molecules that selectively modulate galectin-3 function toward neuroprotective phenotypes. Several experimental studies using different approaches and methods have demonstrated both protective and deleterious effects of galectin-3 in neuroinflammatory diseases. According to the crucial role of galectin-3 in modulation of innate immune response in brain, it is an attractive target in drug discovery of neurodegenerative diseases. The current insight attempts to provide an updated and balanced discussion on the role of galectin-3 as a complex endogenous immune modulator. This helps to have a better insight into the development of galectin-3 modulators with translational value in different neurological disorders including stroke and neurodegenerative diseases, such as Alzheimer's disease, Huntington's disease and Parkinson's disease.

Galectins and their involvement in ocular disease and development

Galectins are carbohydrate binding proteins with high affinity to ß-galactoside containing glycoconjugates. Understanding of the functions of galectins has grown steadily over the past decade, as a result of substantial advancements in the field of glycobiology. Galectins have been shown to be versatile molecules that participate in a range of important biological systems, including inflammation, neovascularisation and fibrosis. These processes are of particular importance in ocular tissues, where a major theme of recent research has been to divert diseases away from pathways which result in loss of function into pathways of repair and regeneration. This review summarises our current understanding of galectins in the context important ocular diseases, followed by an update on current clinical studies and future directions.

Neuroinflammation and oxidative stress act in concert to promote neurodegeneration in the diabetic retina and optic nerve: galectin-3 participation

Diabetes is a lifelong disease characterized by glucose metabolic imbalance, in which low insulin levels or impaired insulin signaling lead to hyperglycemic state. Within 20 years of diabetes progression, 95% of patients will have diabetic retinopathy, the leading cause of visual defects in working-age people worldwide. Although diabetes is considered a microvascular disease, recent studies have shown that neurodegeneration precedes vascular changes within the diabetic visual system, albeit its mechanisms are still under investigation. Neuroinflammation and oxidative stress are intrinsically related phenomena, since macrophage/microglia and astrocytes are the main sources of reactive oxygen species during central nervous system chronic degenerative diseases, and both pathological processes are increased in the visual system during diabetes. The present review will focus on recent findings of the contribution of oxidative stress derived from neuroinflammation in the early neurodegenerative aspects of the diabetic visual system and their relationship with galectin-3.

Clinical significance of galectin-3 expression in malformed hepatic venous tissue

Background & objectives:

Hepatic venous malformation gradually develops over time and exhibits the malignant biological behaviours of being locally invasive, causing morphological and functional damage to local tissue, and may even cause systemic coagulopathy. Studies show that galectin-3(Gal-3) expression is closely associated with local invasion of malignant tumours. In this study an attempt was made to assess the clinical significance of Gal-3 in local invasion during hepatic venous malformation in patients.

Methods:

Gal-3 protein and its mRNA expression were examined using immunohistochemistry and in situ hybridization in a total of 126 patients with hepatic venous malformation. For control tissue, 20 cases of normal tissue distal to surgical margins were also examined. In addition, the association between Gal-3 expression and pathological parameters was analyzed in hepatic venous malformation patients.

Results:

Gal-3 mRNA positivity was observed in 65.08 per cent (82/126) of hepatic venous malformation tissue samples, which was higher than the rate of 20 per cent (4/20) (P<0.05) seen in control tissues. Gal-3 protein positivity was observed in 58.73 per cent (74/126) of hepatic venous malformation tissue samples, which was higher than the rate of 15 per cent (3/20) (P<0.05) seen in the normal tissue. Gal-3 expression was not significantly associated with age or gender. However, there was a significant association between Gal-3 positivity and lesion size, local invasion depth, and involvement with the hepatic vein and the portal system.

Interpretation & conclusions:

Local tissue invasion and destruction by hepatic venous malformation may be related to the upregulation of Gal-3. Gal-3 expression and the development of venous malformation may be related and needs to be studied further.

Functional and morphologic study of retinal hypoperfusion injury induced by bilateral common carotid artery occlusion in rats

Retinal hypoperfusion injury is the pathophysiologic basis of ocular ischemic syndrome (OIS) which often leads to severe visual loss. In this study, we aimed to establish a rat model of retinal chronic hypoperfusion by bilateral common carotid artery occlusion (BCCAO) and observe changes in the retinal function and morphology. We found that model rats showed retinal arteriosclerosis, slight dilated retinal vein, small hemangiomas, hemorrhages, vascular segmental filling, and nonperfused areas after 2 weeks of BCCAO. In the model rats, the retinal circulation time was significantly prolonged by fluorescein fundus angiography (FFA), the latency of a and b waves was delayed and the amplitude was decreased significantly at each time point by electroretinogram (ERG), and the perfusion of the eyes continued to reduced. Morphologic and ultrastructural changes covered that the retinal ganglion cells (RGCs) presented obvious apoptosis and the thickness in the retinal layers were significantly thinner. Collectively, these findings suggested that BCCAO induced retinal hypoperfusion injury in the model rats, thus providing an ideal animal model for the study of OIS.

Focal, but not global, cerebral ischaemia causes loss of myenteric neurons and upregulation of vasoactive intestinal peptide in mouse ileum

Reduced blood flow to the brain induces cerebral ischaemia, potentially causing central injury and peripheral complications including gastrointestinal (GI) dysfunction. The pathophysiology behind GI symptoms is suspected to be neuropathy in the enteric nervous system (ENS), which is essential in regulating GI function. This study investigates if enteric neuropathy occurs after cerebral ischaemia, by analysing neuronal survival and relative numbers of vasoactive intestinal peptide (VIP) and neuronal nitric oxide synthase (nNOS) expressing neurons in mouse ileum after three types of cerebral ischaemia. Focal cerebral ischaemia, modelled by permanent middle cerebral artery occlusion (pMCAO) and global cerebral ischaemia, modelled with either transient occlusion of both common carotid arteries followed by reperfusion (GCIR) or chronic cerebral hypoperfusion (CCH) was performed on C56BL/6 mice. Sham-operated mice for each ischaemia model served as control. Ileum was collected after 1-17 weeks, depending on model, and analysed using morphometry and immunocytochemistry. For each group, intestinal mucosa and muscle layer thicknesses, neuronal numbers and relative proportions of neurons immunoreactive (IR) for nNOS or VIP were estimated. No alterations in mucosa or muscle layer thicknesses were noted in any of the groups. Loss of myenteric neurons and an increased number of VIP-IR submucous neurons were found in mouse ileum 7 days after pMCAO. None of the global ischaemia models showed any alterations in neuronal survival or relative numbers of VIP- and nNOS-IR neurons. We conclude that focal cerebral ischaemia and global cerebral ischaemia influence enteric neuronal survival differently. This is suggested to reflect differences in peripheral neuro-immune responses.

Retinal neuroinflammatory induced neuronal degeneration - Role of toll-like receptor-4 and relationship with gliosis

The purpose of this study was to explore retina-intrinsic neuroinflammatory reactions, effects on neuronal survival, relationship with classic gliosis, and possible role of the toll-like receptor 4 (TLR4). To isolate the adult retina from the systemic immune system, a previously described large animal explant culture model was used in which full-thickness porcine retinal sheets can be kept in vitro for extended time periods. Explants were kept for 5 days in vitro (DIV) and were treated with either; lipopolysaccharide (LPS), a Toll-like receptor-4 (TLR4) inhibitor (CLI-095), LPS + CLI-095, or solvent vehicle throughout the culture period after which retinal sections were examined with hematoxylin and eosin staining and extensive immunohistochemistry. In addition, culture medium from all explant groups was assayed for a panel of cytokines at 2 and 5DIV. Compared with in vivo controls, vehicle controls (CT) as well as CLI-095 explants displayed moderate reduction of total thickness and number of retinal neurons with upregulation of glial fibrillary acidic protein (GFAP) throughout the Müller cells. In contrast, LPS and LPS + CLI-095 treated counterparts showed extensive overall thinning with widespread neuronal degeneration but only minimal signs of classical Müller cell gliosis (limited upregulation of GFAP and no downregulation of glutamine synthetase (GS). These specimens also displayed a significantly increased expression of galectin-3 and TGF-beta activated kinase 1 (TAK1). Multiplex proteomic analysis of culture medium at 2DIV revealed elevated levels of IL-1β, IL-6, IL-4 and IL-12 in LPS-treated explants compared to CLI-095 and CT counterparts. LPS stimulation of the isolated adult retina results in substantial neuronal cell death despite only minimal signs of gliosis indicating a retina-intrinsic neuroinflammatory response directly related to the degenerative process. This response is characterized by early upregulation of several inflammatory related cytokines with subsequent upregulation of Galectin-3, TLR4 and TAK1. Pharmacological block of TLR4 does not attenuate neuronal loss indicating that LPS induced retinal degeneration is mediated by TLR4 independent neuroinflammatory pathways.

Galectin-3: an emerging biomarker in stroke and cerebrovascular diseases

The carbohydrate-binding molecule galectin-3 has garnered significant attention recently as a biomarker for various conditions ranging from cardiac disease to obesity. Although there have been several recent studies investigating its role in stroke and other cerebrovascular diseases, awareness of this emerging biomarker in the wider neurology community is limited. We performed a systematic search in PubMed, Embase, Scopus, CINAHL, Clinicaltrials.gov and the Cochrane library in November and December 2016 for articles related to galectin-3 and cerebrovascular disease. We included both human and pre-clinical studies in order to provide a comprehensive view of the state of the literature on this topic. The majority of the relevant literature focuses on stroke, cerebral ischemia and atherosclerosis, but some recent attention has also been devoted to intracranial and subarachnoid hemorrhage. Higher blood levels of galectin-3 correlate with worse outcomes in atherosclerotic disease as well as in intracranial and subarachnoid hemorrhage in human studies. However, experimental evidence supporting the role of galectin-3 in these phenotypes is not as robust. It is likely that the role of galectin-3 in the inflammatory cascade within the central nervous system following injury is responsible for many of its effects, but its varied physiological functions and multiple sites of expression mean that it may have different effects depending on the nature of the disease condition and the time since injury. In summary, experimental and human research raises the possibility that galectin-3, which is closely linked to the inflammatory cascade, could be of value as a prognostic marker and therapeutic target in cerebrovascular disease.

Pingyangmycin Pretreatment Influences the Biological Behavior of Ocular Venous Malformation and Relates with Galectin-3 Expression

BACKGROUND

Galectin-3 (Gal-3) plays a role in the mechanisms underlying ocular venous malformation. We conducted this study to investigate the effect of pingyangmycin pretreatment on the Gal-3 expressions and biological behavior of ocular venous malformation.

METHODS

Tissue samples were collected from 136 patients with ocular venous malformation. Patients were randomly divided into pingyangmycin (n = 69) and nonpingyangmycin group (n = 67). Patients in the pingyangmycin group received a local injection of 0.02% pingyangmycin once every 2 days for 2 weeks (7 doses) before removal surgery, whereas patients in the nonpingyangmycin group underwent removal surgery without local injection. The protein and messenger RNA (mRNA) expression of Gal-3 were detected by using immunohistochemistry and in situ hybridization.

RESULTS

Gal-3 protein was expressed in 35 (52%) of 67 samples in the nonpingyangmycin group and in 19 (28%) of 69 samples in the pingyangmycin group (P < 0.05). Gal-3 mRNA expression was detected in 39 (58%) of 67 samples in the nonpingyangmycin group and 22 (32%) of 69 samples in the pingyangmycin group (P < 0.05). The higher Gal-3 expressions were detected in samples with deeper invasiveness than those with superficial invasiveness before (χ2 = 12.720 and 13.369, respectively, both P < 0.05) and after pingyangmycin treatment (χ2 = 8.429 and 4.590, respectively, both P < 0.05). It was more frequently detected in mesh-like lesions with unclear boundary than round lesions with clear boundary before (χ2 = 30.291 and 41.466, respectively, both P < 0.05) and after pingyangmycin treatment (χ2 = 14.619 and 15.130, respectively, both P < 0.05). Pingyangmycin treatment led to a significant difference in Gal-3 expressions at both protein and mRNA levels (χ2 = 8.664 and 9.524, respectively, both P < 0.05).

CONCLUSIONS

Gal-3 expression may be involved in the development and invasiveness of ocular venous malformation, and pingyangmycin can inhibit Gal-3 expression, indicating a role of pingyangmycin treatment before the removal of ocular venous malformation.

The Role of Mitochondria, Oxidative Stress, and the Radical-binding Protein A1M in Cultured Porcine Retina

PURPOSE

The purpose of this study was to explore the relationship between oxidative stress, antioxidant defense, mitochondrial structure, and biomechanical tissue support in the isolated porcine retina.

METHODS

Full-thickness retinal sheets were isolated from adult porcine eyes. Retinas were cultured for 2 or 48 h using (1) a previously established low-support explant protocol with photoreceptors positioned against the culture membrane (porous polycarbonate) or (2) a high-support procedure developed by our group, apposing the Müller cell endfeet and inner limiting membrane against the membrane. The grafts were analyzed by quantitative polymerase chain reaction (PCR), immunohistochemistry, and transmission electron microscopy (TEM), and culture medium was assayed for the cell damage and oxidative stress markers lactate dehydrogenase and protein carbonyls.

RESULTS

In explants cultured with physical support to the inner border, cone photoreceptors were preserved and lactate dehydrogenase levels were reduced, although an initial (2 h), transient, increased oxidative stress was observed. Elevated expression of the antioxidants α₁-microglobulin and heme oxygenase-1 was seen in the mitochondria-rich inner segments after 48 h compared to low-support counterparts. Housekeeping gene expression suggested a higher degree of structural integrity of mitochondria in high-support explants, and TEM of inner segments confirmed preservation of a normal mitochondrial morphology.

CONCLUSION

Providing retinal explants with inner retinal support leads to mobilization of antioxidant proteins, preservation of mitochondrial function, and increased cell viability. Consequently, the failure of low-support retinal cultures to mobilize an adequate response to the oxidative environment may play a key role in their rapid demise. These findings shed new light on pathological reactions in biomechanically related conditions in vivo.

Specific inhibition of TRPV4 enhances retinal ganglion cell survival in adult porcine retinal explants

Signaling through the polymodal cation channel Transient Receptor Potential Vanilloid 4 (TRPV4) has been implicated in retinal neuronal degeneration. To further outline the involvement of this channel in this process, we here explore modulation of Transient Receptor Potential Vanilloid 4 (TRPV4) activity on neuronal health and glial activation in an in vitro model of retinal degeneration. For this purpose, adult porcine retinal explants were cultured using a previously established standard protocol for up to 5 days with specific TRPV4 agonist GSK1016790A (GSK), or specific antagonist RN-1734, or culture medium only. Glial and neuronal cell health were evaluated by a battery of immunohistochemical markers, as well as morphological staining. Specific inhibition of TRPV4 by RN-1734 significantly enhanced ganglion cell survival, improved the maintenance of the retinal laminar architecture, reduced apoptotic cell death and attenuated the gliotic response as well as preserved the expression of TRPV4 in the plexiform layers and ganglion cells. In contrast, culture controls, as well as specimens treated with GSK, displayed rapid remodeling and neurodegeneration as well as a downregulation of TRPV4 and the Müller cell homeostatic mediator glutamine synthetase. Our results indicate that TRPV4 signaling is an important contributor to the retinal degeneration in this model, affecting neuronal cell health and glial homeostasis. The finding that pharmacological inhibition of the receptor significantly attenuates neuronal degeneration and gliosis in vitro, suggests that TRPV4 signaling may be an interesting pharmaceutical target to explore for treatment of retinal degenerative disease.

Complimentary action: C1q increases ganglion cell survival in an in vitro model of retinal degeneration

Using a previously described retinal explant culture system as an acute injury model, we here explore the role of C1q, the initiator of the classical complement pathway, in neuronal cell survival and retinal homeostasis. Full-thickness adult rat retinal explants were divided into four groups, receiving the following supplementation: C1q (50nM), C1-inhibitor (C1-inh; Berinert; 500mg/l), C1q+C1-inh, and no supplementation (culture controls). Explants were kept for 12h or 2days after which they were examined morphologically and with a panel of immunohistochemical markers. C1q supplementation protects ganglion cells from degeneration within the explant in vitro system. This effect is correlated to an attenuated endogenous production of C1q, and a quiesced gliotic response.

Galectin-3 causes enteric neuronal loss in mice after left sided permanent middle cerebral artery occlusion, a model of stroke

In addition to brain injury stroke patients often suffer gastrointestinal complications. Neuroimmune interactions involving galectin-3, released from microglia in the brain, mediates the post-stroke pro-inflammatory response. We investigated possible consequences of stroke on the enteric nervous system and the involvement of galectin-3. We show that permanent middle cerebral artery occlusion (pMCAO) induces loss of enteric neurons in ileum and colon in galectin-3(+/+), but not in galectin-3(-/-), mice. In vitro we show that serum from galectin-3(+/+), but not from galectin-3(-/-), mice subjected to pMCAO, caused loss of C57BL/6J myenteric neurons, while myenteric neurons derived from TLR4(-/-) mice were unaffected. Further purified galectin-3 (10(-6) M) caused loss of cultured C57BL/6J myenteric neurons. Inhibitors of transforming growth factor β-activated kinase 1 (TAK1) or AMP activated kinase (AMPK) counteracted both the purified galectin-3 and the galectin-3(+/+) pMCAO serum-induced loss in vitro. Combined we show that stroke (pMCAO) triggers central and peripheral galectin-3 release causing enteric neuronal loss through a TLR4 mediated mechanism involving TAK1 and AMPK. Galectin-3 is suggested a target for treatment of post-stroke complications.

Inflamed In Vitro Retina: Cytotoxic Neuroinflammation and Galectin-3 Expression

Background

Disease progression in retinal neurodegeneration is strongly correlated to immune cell activation, which may have either a neuroprotective or neurotoxic effect. Increased knowledge about the immune response profile and retinal neurodegeneration may lead to candidate targets for treatments. Therefore, we have used the explanted retina as a model to explore the immune response and expression of the immune modulator galectin-3 (Gal-3), induced by the cultivation per se and after additional immune stimulation with lipopolysaccharide (LPS), and how this correlates with retinal neurotoxicity.

Methods

Post-natal mouse retinas were cultured in a defined medium. One group was stimulated with LPS (100 ng/ml, 24 h). Retinal architecture, apoptotic cell death, and micro- and macroglial activity were studied at the time of cultivation (0 days in vitro (DIV)) and at 3, 4 and 7 DIV using morphological staining, biochemical- and immunohistochemical techniques.

Results

Our results show that sustained activation of macro- and microglia, characterized by no detectable cytokine release and limited expression of Gal-3, is not further inducing apoptosis additional to the axotomy-induced apoptosis in innermost nuclear layer. An elevated immune response was detected after LPS stimulation, as demonstrated primarily by release of immune mediators (i.e. interleukin 2 (IL-2), IL-6, KC/GRO (also known as CLCX1) and tumour necrosis factor-α (TNF-α)), increased numbers of microglia displaying morphologies of late activation stages as well as Gal-3 expression. This was accompanied with increased apoptosis in the two additional nuclear layers, and damage to retinal gross architecture.

Conclusion

We demonstrate that an immune response characterized by sustained and increased release of cytokines, along with an increase in Gal-3 expression, is accompanied by significant increased neurotoxicity in the explanted retina. Further investigations using the current setting may lead to increased understanding on the mechanisms involved in neuronal loss in retinal neurodegenerations.

N-methyl-N-nitrosourea-induced neuronal cell death in a large animal model of retinal degeneration in vitro

N-methyl-N-nitrosourea (MNU) has been reported to induce photoreceptor-specific degeneration with minimal inner retinal impact in small animals in vivo. Pending its use within a retinal transplantation paradigm, we here explore the effects of MNU on outer and inner retinal neurons and glia in an in vitro large animal model of retinal degeneration. The previously described degenerative culture explant model of adult porcine retina was used and compared with explants receiving 10 or 100 μg/ml MNU (MNU10 and MNU100) supplementation. All explants were kept for 5 days in vitro, and examined for morphology as well as for glial and neuronal immunohistochemical markers. Rhodopsin-labeled photoreceptors were present in all explants. The number of cone photoreceptors (transducin), rod bipolar cells (PKC) and horizontal cells (calbindin) was significantly lower in MNU treated explants (p < 0.001). Gliosis was attenuated in MNU10 treated explants, with expression of vimentin, glial fibrillary protein (GFAP), glutamine synthetase (GS), and bFGF comparable to in vivo controls. In corresponding MNU100 counterparts, the expression of Müller cell proteins was almost extinguished. We here show that MNU causes degeneration of outer and inner retinal neurons and glia in the adult porcine retina in vitro. MNU10 explants display attenuation of gliosis, despite decreased neuronal survival compared with untreated controls. Our results have impact on the use of MNU as a large animal photoreceptor degeneration model, on tissue engineering related to retinal transplantation, and on our understanding of gliosis related neuronal degenerative cell death.

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.