Activation of p38 Mitogen-Activated Protein Kinase in Gaucher's Disease

Exploring Pro-Inflammatory Immunological Mediators: Unraveling the Mechanisms of Neuroinflammation in Lysosomal Storage Diseases

Lysosomal storage diseases are a group of rare and ultra-rare genetic disorders caused by defects in specific genes that result in the accumulation of toxic substances in the lysosome. This excess accumulation of such cellular materials stimulates the activation of immune and neurological cells, leading to neuroinflammation and neurodegeneration in the central and peripheral nervous systems. Examples of lysosomal storage diseases include Gaucher, Fabry, Tay–Sachs, Sandhoff, and Wolman diseases. These diseases are characterized by the accumulation of various substrates, such as glucosylceramide, globotriaosylceramide, ganglioside GM2, sphingomyelin, ceramide, and triglycerides, in the affected cells. The resulting pro-inflammatory environment leads to the generation of pro-inflammatory cytokines, chemokines, growth factors, and several components of complement cascades, which contribute to the progressive neurodegeneration seen in these diseases. In this study, we provide an overview of the genetic defects associated with lysosomal storage diseases and their impact on the induction of neuro-immune inflammation. By understanding the underlying mechanisms behind these diseases, we aim to provide new insights into potential biomarkers and therapeutic targets for monitoring and managing the severity of these diseases. In conclusion, lysosomal storage diseases present a complex challenge for patients and clinicians, but this study offers a comprehensive overview of the impact of these diseases on the central and peripheral nervous systems and provides a foundation for further research into potential treatments.

The protective role of glucocerebrosidase/ceramide in rheumatoid arthritis

OBJECTIVE

To clarify the role of glucocerebrosidase (GBA) and Ceramide (Cer) in rheumatoid arthritis (RA).

METHODS

GBA-expressing lentivirus were constructed and injected into collagen-induced arthritis (CIA) mice, and compared with CIA mice injected with empty vector. The severity of arthritis and inflammatory mediators were evaluated. Fibroblast-like synoviocytes (FLS) from RA patients were transfected with GBA-expressing lentivirus, or pretreated with C6-Cer. The migration and invasion of FLS, the production of inflammatory cytokines, and the relevant signaling pathways were assessed.

RESULTS

In CIA mice, GBA markedly improved arthritis compared to that in the CIA mice, with increased content of proteoglycan and integral cartilage surfaces and tidemarks. The circulating inflammatory mediators, including interleukin (IL)-1β, IL-6, IL-18, and matrix metalloproteinase (MMP)-1, were significantly reduced in CIA mice with GBA overexpression compared to those in CIA mice. GBA and C6-Cer treatment inhibited migration and invasion of FLS, and suppressed production of inflammatory cytokines and activation of the MAPK pathways.

CONCLUSION

GBA/Cer exhibited a protective role in CIA mice and RA FLS. These results highlight the potential of targeting GBA/Cer as a therapeutic strategy in RA and warrant further investigation.

C5a Activates a Pro-Inflammatory Gene Expression Profile in Human Gaucher iPSC-Derived Macrophages

Gaucher disease (GD) is an autosomal recessive disorder caused by bi-allelic GBA1 mutations that reduce the activity of the lysosomal enzyme β-glucocerebrosidase (GCase). GCase catalyzes the conversion of glucosylceramide (GluCer), a ubiquitous glycosphingolipid, to glucose and ceramide. GCase deficiency causes the accumulation of GluCer and its metabolite glucosylsphingosine (GluSph) in a number of tissues and organs. In the immune system, GCase deficiency deregulates signal transduction events, resulting in an inflammatory environment. It is known that the complement system promotes inflammation, and complement inhibitors are currently being considered as a novel therapy for GD; however, the mechanism by which complement drives systemic macrophage-mediated inflammation remains incompletely understood. To help understand the mechanisms involved, we used human GD-induced pluripotent stem cell (iPSC)-derived macrophages. We found that GD macrophages exhibit exacerbated production of inflammatory cytokines via an innate immune response mediated by receptor 1 for complement component C5a (C5aR1). Quantitative RT-PCR and ELISA assays showed that in the presence of recombinant C5a (rC5a), GD macrophages secreted 8-10-fold higher levels of TNF-α compared to rC5a-stimulated control macrophages. PMX53, a C5aR1 blocker, reversed the enhanced GD macrophage TNF-α production, indicating that the observed effect was predominantly C5aR1-mediated. To further analyze the extent of changes induced by rC5a stimulation, we performed gene array analysis of the rC5a-treated macrophage transcriptomes. We found that rC5a-stimulated GD macrophages exhibit increased expression of genes involved in TNF-α inflammatory responses compared to rC5a-stimulated controls. Our results suggest that rC5a-induced inflammation in GD macrophages activates a unique immune response, supporting the potential use of inhibitors of the C5a-C5aR1 receptor axis to mitigate the chronic inflammatory abnormalities associated with GD.

Trends in Glucocerebrosides Research: A Systematic Review

Glucocerebrosides are sphingolipid components of cell membranes that intervene in numerous cell biological processes and signaling pathways and that deregulation is implicated in human diseases such as Gaucher disease and Parkinson's disease. In the present study, we conducted a systematic review using document co-citation analysis, clustering and visualization tools to explore the trends and knowledge structure of glucocerebrosides research as indexed in the Science Citation Index Expanded database (1956-present). A co-citation network of 5,324 publications related to glucocerebrosides was constructed. The analysis of emerging categories and keywords suggested a growth of research related to neurosciences over the last decade. We identified ten major areas of research (e.g., clusters) that developed over time, from the oldest (i.e., on glucocerebrosidase protein or molecular analysis of the GBA gene) to the most recent ones (i.e., on drug resistance in cancer, pharmacological chaperones, or Parkinson's disease). We provided for each cluster the most cited publications and a description of their intellectual content. We moreover identified emerging trends in glucocerebrosides research by detecting the surges in the rate of publication citations in the most recent years. In conclusion, this study helps to apprehend the most significant lines of research on glucocerebrosides. This should strengthen the connections between scientific communities studying glycosphingolipids to facilitate advances, especially for the most recent researches on cancer drug resistance and Parkinson's disease.

Are Glucosylceramide-Related Sphingolipids Involved in the Increased Risk for Cancer in Gaucher Disease Patients? Review and Hypotheses

The roles of ceramide and its catabolites, i.e., sphingosine and sphingosine 1-phosphate, in the development of malignancies and the response to anticancer regimens have been extensively described. Moreover, an abundant literature points to the effects of glucosylceramide synthase, the mammalian enzyme that converts ceramide to β-glucosylceramide, in protecting tumor cells from chemotherapy. Much less is known about the contribution of β-glucosylceramide and its breakdown products in cancer progression. In this chapter, we first review published and personal clinical observations that report on the increased risk of developing cancers in patients affected with Gaucher disease, an inborn disorder characterized by defective lysosomal degradation of β-glucosylceramide. The previously described mechanistic links between lysosomal β-glucosylceramidase, β-glucosylceramide and/or β-glucosylphingosine, and various hallmarks of cancer are reviewed. We further show that melanoma tumor growth is facilitated in a Gaucher disease mouse model. Finally, the potential roles of the β-glucosylceramidase protein and its lipidic substrates and/or downstream products are discussed.

Gene expression profile in patients with Gaucher disease indicates activation of inflammatory processes

Gaucher disease (GD) is a rare inherited metabolic disease caused by pathogenic variants in the GBA1 gene. So far, the pathomechanism of GD was investigated mainly in animal models. In order to delineate the molecular changes in GD cells we analysed gene expression profile in cultured skin fibroblasts from GD patients, control individuals and, additionally, patients with Niemann-Pick type C disease (NPC). We used expression microarrays with subsequent validation by qRT-PCR method. In the comparison GD patients vs. controls, the most pronounced relative fold change (rFC) in expression was observed for genes IL13RA2 and IFI6 (up-regulated) and ATOH8 and CRISPLD2 (down-regulated). Products of up-regulated and down-regulated genes were both enriched in genes associated with immune response. In addition, products of down-regulated genes were associated with cell-to-cell and cell-to-matrix interactions, matrix remodelling, PI3K-Akt signalling pathway and a neuronal survival pathway. Up-regulation of PLAU, IFIT1, TMEM158 and down-regulation of ATOH8 and ISLR distinguished GD patients from both NPC patients and healthy controls. Our results emphasize the inflammatory character of changes occurring in human GD cells indicating that further studies on novel therapeutics for GD should consider anti-inflammatory agents.

A new hypothesis for Parkinson's disease pathogenesis: GTPase-p38 MAPK signaling and autophagy as convergence points of etiology and genomics

The combination of genetics and genomics in Parkinson´s disease has recently begun to unveil molecular mechanisms possibly underlying disease onset and progression. In particular, catabolic processes such as autophagy have been increasingly gaining relevance as post-mortem evidence and experimental models suggested a participation in neurodegeneration and alpha-synuclein Lewy body pathology. In addition, familial Parkinson´s disease linked to LRRK2 and alpha-synuclein provided stronger correlation between etiology and alterations in autophagy. More detailed cellular pathways are proposed and genetic risk factors that associate with idiopathic Parkinson´s disease provide further clues in dissecting contributions of single players. Nevertheless, the fine-tuning of these processes remains elusive, as the initial stages of the pathways are not yet clarified.In this review, we collect literature evidence pointing to autophagy as the common, downstream target of Parkinsonian dysfunctions and augment current knowledge on the factors that direct the subsequent steps. Cell and molecular biology evidence indicate that p38 signaling underlies neurodegeneration and autoptic observations suggest a participation in neuropathology. Moreover, alpha-synuclein and LRRK2 also appear involved in the p38 pathway with additional roles in the regulation of GTPase signaling. Small GTPases are critical modulators of p38 activation and thus, their functional interaction with aSyn and LRRK2 could explain much of the detailed mechanics of autophagy in Parkinson´s disease.We propose a novel hypothesis for a more comprehensive working model where autophagy is controlled by upstream pathways, such as GTPase-p38, that have been so far underexplored in this context. In addition, etiological factors (LRRK2, alpha-synuclein) and risk loci might also combine in this common mechanism, providing a powerful experimental setting to dissect the cause of both familial and idiopathic disease.

Molecular regulations and therapeutic targets of Gaucher disease

Gaucher disease (GD) is the most common lysosomal storage disease caused by deficiency of beta-glucocerebrosidase (GCase) resulting in lysosomal accumulation of its glycolipid substrate glucosylceramide. The activity of GCase depends on many factors such as proper folding and lysosomal localization, which are influenced by mutations in GCase encoding gene, and regulated by various GCase-binding partners including Saposin C, progranulin and heat shock proteins. In addition, proinflammatory molecules also contribute to pathogenicity of GD. In this review, we summarize the molecules that are known to be important for the pathogenesis of GD, particularly those modulating GCase lysosomal appearance and activity. In addition, small molecules that inhibit inflammatory mediators, calcium ion channels and other factors associated with GD are also described. Discovery and characterization of novel molecules that impact GD are not only important for deciphering the pathogenic mechanisms of the disease, but they also provide new targets for drug development to treat the disease.

Dual-specificity phosphatase 6 (DUSP6): a review of its molecular characteristics and clinical relevance in cancer

Mitogen-activated protein kinases (MAPKs) are the main regulators of cellular proliferation, growth, and survival in physiological or pathological conditions. Aberrant MAPK signaling plays a pivotal role in carcinogenesis, which leads to development and progression of human cancer. Dual-specificity phosphatase 6 (DUSP6), a member of the MAPK phosphatase family, interacts with specifically targeted extracellular signal-regulated kinase 1/2 via negative feedback regulation in the MAPK pathway of mammalian cells. This phosphatase functions in a dual manner, pro-oncogenic or tumor-suppressive, depending on the type of cancer. To date, the tumor-suppressive role of DUSP6 has been demonstrated in pancreatic cancer, non-small cell lung cancer, esophageal squamous cell and nasopharyngeal carcinoma, and ovarian cancer. Its pro-oncogenic role has been observed in human glioblastoma, thyroid carcinoma, breast cancer, and acute myeloid carcinoma. Both roles of DUSP6 have been documented in malignant melanoma depending on the histological subtype of the cancer. Loss- or gain-of-function effects of DUSP6 in these cancers highlights the significance of this phosphatase in carcinogenesis. Development of methods that use the DUSP6 gene as a therapeutic target for cancer treatment or as a prognostic factor for diagnosis and evaluation of cancer treatment outcome has great potential. This review focuses on molecular characteristics of the DUSP6 gene and its role in cancers in the purview of development, progression, and cancer treatment outcome.

Overview of Inflammation in Neurometabolic Diseases

Neuroinflammation is an intrinsic component of the neurodegeneration of inborn errors of neurometabolic diseases. Diseases resulting in lysosomal, peroxisomal, and autophagocytic disruption lead to neuroinflammation by different mechanisms relating to accumulated substrates and/or downstream deficiencies that cause presymptomatic microglial activation, axonal instabilities and/or direct hyperactivation of intrinsic inflammatory mechanisms. Only in selected diseases is the blood-brain barrier (BBB) breached, thereby permitting peripheral adaptive immune mechanisms to amplify intrinsic immune reactions in the central nervous system. These result in evoking several different programmed cell death pathways, including apoptosis, necroptosis, and pyroptosis, with the subsequent neuronal death of specific types and in selected regions of the brain or spinal cord. In addition to correction of the primary genetic or metabolic defects, successful therapeutic interventions require greater molecular understanding of the specific neuroinflammatory components of neurometabolic diseases to permit identification of significant targets for intervention.

Osteocyte Alterations Induce Osteoclastogenesis in an In Vitro Model of Gaucher Disease

Gaucher disease (GD) is caused by mutations in the glucosylceramidase β (GBA 1) gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to the accumulation of the glycolipid glucocerebroside in the lysosomes of cells, mainly in the monocyte/macrophage lineage. Its mildest form is Type I GD, characterized by non-neuronopathic involvement. Bone compromise is the most disabling aspect of the Gaucher disease. However, the pathophysiological aspects of skeletal alterations are not yet fully understood. The bone tissue homeostasis is maintained by a balance between resorption of old bone by osteoclasts and new bone formation by osteoblasts. A central player in this balance is the osteocyte as it controls both processes. We studied the involvement of osteocytes in an in vitro chemical model of Gaucher disease. The osteocyte cell line MLO-Y4 was exposed to conduritol-β-epoxide (CBE), an inhibitor of GCase, for a period of 7, 14 and 21 days. Conditioned media from CBE-treated osteocytes was found to induce osteoclast differentiation. GCase inhibition caused alterations in Cx43 expression and distribution pattern and an increase in osteocyte apoptosis. Osteoclast differentiation involved osteocyte apoptotic bodies, receptor activator of nuclear factor κ-B ligand (RANKL) and soluble factors. Thus, our results indicate that osteocytes may have a role to play in the bone pathophysiology of GD.

Ten plus one challenges in diseases of the lysosomal system

The advent of the first effective specific therapy for a lysosomal storage disease (LSDs), Gaucher disease type 1, by Roscoe O. Brady was foundational for development of additional treatments for this group of rare diseases. The past 26years, since the approval of enzyme therapy for Gaucher disease type 1, have witnessed a burgeoning understanding of LSDs at genetic, molecular, biochemical, cell biologic, and clinical levels. Simultaneously, this expansion of knowledge has exposed our incomplete understanding of the individual pathophysiologies of LSDs as well as difficult challenges for improvement in therapy and therapeutic outcomes for afflicted individuals. Here, 10 such challenges/problems representing major impediments, which need to be overcome, to move forward toward the goals of more effective and complete therapies for these devastating diseases.

Advances in GBA-associated Parkinson's disease--Pathology, presentation and therapies

GBA mutations are to date the most common genetic risk factor for Parkinson's disease. The GBA gene encodes the lysomal hydrolase glucocerebrosidase. Whilst bi-allelic GBA mutations cause Gaucher disease, both mono- and bi-allelic mutations confer risk for Parkinson's disease. Clinically, Parkinson's disease patients with GBA mutations resemble idiopathic Parkinson's disease patients. However, these patients have a modest reduction in age-of-onset of disease and a greater incidence of cognitive decline. In some cases, GBA mutations are also responsible for familial Parkinson's disease. The accumulation of α-synuclein into Lewy bodies is the central neuropathological hallmark of Parkinson's disease. Pathologic GBA mutations reduce enzymatic function. A reduction in glucocerebrosidase function increases α-synuclein levels and propagation, which in turn inhibits glucocerebrosidase in a feed-forward cascade. This cascade is central to the neuropathology of GBA-associated Parkinson's disease. The lysosomal integral membrane protein type-2 is necessary for normal glucocerebrosidase function. Glucocerebrosidase dysfunction also increases in the accumulation of β-amyloid and amyloid-precursor protein, oxidative stress, neuronal susceptibility to metal ions, microglial and immune activation. These factors contribute to neuronal death. The Mendelian Parkinson's disease genes, Parkin and ATP13A2, intersect with glucocerebrosidase. These factors sketch a complex circuit of GBA-associated neuropathology. To clinically interfere with this circuit, central glucocerebrosidase function must be improved. Strategies based on reducing breakdown of mutant glucocerebrosidase and increasing the fraction that reaches the lysosome has shown promise. Breakdown can be reduced by interfering with the ability of heat-shock proteins to recognize mutant glucocerebrosidase. This underlies the therapeutic efficacy of certain pharmacological chaperones and histone deacetylase inhibitors. These therapies are promising for Parkinson's disease, regardless of mutation status. Recently, there has been a boom in studies investigating the role of glucocerebrosidase in the pathology of Parkinson's disease. This merits a comprehensive review of the current cell biological processes and pathological pictures involving Parkinson's disease associated with GBA mutations.