The inhibition of LSD1 via sequestration contributes to tau-mediated neurodegeneration

Roles of Lysine Methylation in Glucose and Lipid Metabolism: Functions, Regulatory Mechanisms, and Therapeutic Implications

Glucose and lipid metabolism are essential energy sources for the body. Dysregulation in these metabolic pathways is a significant risk factor for numerous acute and chronic diseases, including type 2 diabetes (T2DM), Alzheimer's disease (AD), obesity, and cancer. Post-translational modifications (PTMs), which regulate protein structure, localization, function, and activity, play a crucial role in managing cellular glucose and lipid metabolism. Among these PTMs, lysine methylation stands out as a key dynamic modification vital for the epigenetic regulation of gene transcription. Emerging evidence indicates that lysine methylation significantly impacts glucose and lipid metabolism by modifying key enzymes and proteins. This review summarizes the current understanding of lysine methylation's role and regulatory mechanisms in glucose and lipid metabolism. We highlight the involvement of methyltransferases (KMTs) and demethylases (KDMs) in generating abnormal methylation signals affecting these metabolic pathways. Additionally, we discuss the chemical biology and pharmacology of KMT and KDM inhibitors and targeted protein degraders, emphasizing their clinical implications for diseases such as diabetes, obesity, neurodegenerative disorders, and cancers. This review suggests that targeting lysine methylation in glucose and lipid metabolism could be an ideal therapeutic strategy for treating these diseases.

Novel histone post-translational modifications in Alzheimer's disease: current advances and implications

Alzheimer's disease (AD) has a complex pathogenesis, and multiple studies have indicated that histone post-translational modifications, especially acetylation, play a significant role in it. With the development of mass spectrometry and proteomics, an increasing number of novel HPTMs, including lactoylation, crotonylation, β-hydroxybutyrylation, 2-hydroxyisobutyrylation, succinylation, and malonylation, have been identified. These novel HPTMs closely link substance metabolism to gene regulation, and an increasing number of relevant studies on the relationship between novel HPTMs and AD have become available. This review summarizes the current advances and implications of novel HPTMs in AD, providing insight into the deeper pathogenesis of AD and the development of novel drugs.

Kdm1a safeguards the topological boundaries of PRC2-repressed genes and prevents aging-related euchromatinization in neurons

Kdm1a is a histone demethylase linked to intellectual disability with essential roles during gastrulation and the terminal differentiation of specialized cell types, including neurons, that remains highly expressed in the adult brain. To explore Kdm1a's function in adult neurons, we develop inducible and forebrain-restricted Kdm1a knockouts. By applying multi-omic transcriptome, epigenome and chromatin conformation data, combined with super-resolution microscopy, we find that Kdm1a elimination causes the neuronal activation of nonneuronal genes that are silenced by the polycomb repressor complex and interspersed with active genes. Functional assays demonstrate that the N-terminus of Kdm1a contains an intrinsically disordered region that is essential to segregate Kdm1a-repressed genes from the neighboring active chromatin environment. Finally, we show that the segregation of Kdm1a-target genes is weakened in neurons during natural aging, underscoring the role of Kdm1a safeguarding neuronal genome organization and gene silencing throughout life.

A bibliometric and visual analysis of epigenetic research publications for Alzheimer's disease (2013-2023)

Background

Currently, the prevalence of Alzheimer's disease (AD) is progressively rising, particularly in developed nations. There is an escalating focus on the onset and progression of AD. A mounting body of research indicates that epigenetics significantly contributes to AD and holds substantial promise as a novel therapeutic target for its treatment.

Objective

The objective of this article is to present the AD areas of research interest, comprehend the contextual framework of the subject research, and investigate the prospective direction for future research development.

Methods

ln Web of Science Core Collection (WOSCC), we searched documents by specific subject terms and their corresponding free words. VOSviewer, CiteSpace and Scimago Graphica were used to perform statistical analysis on measurement metrics such as the number of published papers, national cooperative networks, publishing countries, institutions, authors, co-cited journals, keywords, and visualize networks of related content elements.

Results

We selected 1,530 articles from WOSCC from January 2013 to June 2023 about epigenetics of AD. Based on visual analysis, we could get that China and United States were the countries with the most research in this field. Bennett DA was the most contributed and prestigious scientist. The top 3 cited journals were Journal of Alzheimer's Disease, Neurobiology of Aging and Molecular Neurobiology. According to the analysis of keywords and the frequency of citations, ncRNAs, transcription factor, genome, histone modification, blood DNA methylation, acetylation, biomarkers were hot research directions in AD today.

Conclusion

According to bibliometric analysis, epigenetic research in AD was a promising research direction, and epigenetics had the potential to be used as AD biomarkers and therapeutic targets.

Mechanisms and pathology of protein misfolding and aggregation

Despite advances in machine learning-based protein structure prediction, we are still far from fully understanding how proteins fold into their native conformation. The conventional notion that polypeptides fold spontaneously to their biologically active states has gradually been replaced by our understanding that cellular protein folding often requires context-dependent guidance from molecular chaperones in order to avoid misfolding. Misfolded proteins can aggregate into larger structures, such as amyloid fibrils, which perpetuate the misfolding process, creating a self-reinforcing cascade. A surge in amyloid fibril structures has deepened our comprehension of how a single polypeptide sequence can exhibit multiple amyloid conformations, known as polymorphism. The assembly of these polymorphs is not a random process but is influenced by the specific conditions and tissues in which they originate. This observation suggests that, similar to the folding of native proteins, the kinetics of pathological amyloid assembly are modulated by interactions specific to cells and tissues. Here, we review the current understanding of how intrinsic protein conformational propensities are modulated by physiological and pathological interactions in the cell to shape protein misfolding and aggregation pathology.

Histone demethylases in neurodevelopment and neurodegenerative diseases

Neurodevelopment can be precisely regulated by epigenetic mechanisms, including DNA methylations, noncoding RNAs, and histone modifications. Histone methylation was a reversible modification, catalyzed by histone methyltransferases and demethylases. So far, dozens of histone lysine demethylases (KDMs) have been discovered, and they (members from KDM1 to KDM7 family) are important for neurodevelopment by regulating cellular processes, such as chromatin structure and gene transcription. The role of KDM5C and KDM7B in neural development is particularly important, and mutations in both genes are frequently found in human X-linked mental retardation (XLMR). Functional disorders of specific KDMs, such as KDM1A can lead to the development of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Several KDMs can serve as potential therapeutic targets in the treatment of neurodegenerative diseases. At present, the function of KDMs in neurodegenerative diseases is not fully understood, so more comprehensive and profound studies are needed. Here, the role and mechanism of histone demethylases were summarized in neurodevelopment, and the potential of them was introduced in the treatment of neurodegenerative diseases.

Demethylase-independent roles of LSD1 in regulating enhancers and cell fate transition

The major enhancer regulator lysine-specific histone demethylase 1A (LSD1) is required for mammalian embryogenesis and is implicated in human congenital diseases and multiple types of cancer; however, the underlying mechanisms remain enigmatic. Here, we dissect the role of LSD1 and its demethylase activity in gene regulation and cell fate transition. Surprisingly, the catalytic inactivation of LSD1 has a mild impact on gene expression and cellular differentiation whereas the loss of LSD1 protein de-represses enhancers globally and impairs cell fate transition. LSD1 deletion increases H3K27ac levels and P300 occupancy at LSD1-targeted enhancers. The gain of H3K27ac catalyzed by P300/CBP, not the loss of CoREST complex components from chromatin, contributes to the transcription de-repression of LSD1 targets and differentiation defects caused by LSD1 loss. Together, our study demonstrates a demethylase-independent role of LSD1 in regulating enhancers and cell fate transition, providing insight into treating diseases driven by LSD1 mutations and misregulation.

Lysine-Specific Demethylase 1 Promises to Be a Novel Target in Cancer Drug Resistance: Therapeutic Implications

Chemotherapy, targeted therapy, and immunotherapy are effective against most tumors, but drug resistance remains a barrier to successful treatment. Lysine-specific demethylase 1 (LSD1), a member of histone demethylation modifications, can regulate invasion, metastasis, apoptosis, and immune escape of tumor cells, which are associated with tumorigenesis and tumor progression. Recent studies suggest that LSD1 ablation regulates resensitivity of tumor cells to anticarcinogens containing immune checkpoint inhibitors (ICIs) via multiple upstream and downstream pathways. In this review, we describe the recent findings about LSD1 biology and its role in the development and progression of cancer drug resistance. Further, we summarize LSD1 inhibitors that have a reversal or resensitive effect on drug resistance and discuss the possibility of targeting LSD1 in combination with other agents to surmount resistance.

SPR-1/CoREST facilitates the maternal epigenetic reprogramming of the histone demethylase SPR-5/LSD1

Maternal reprogramming of histone methylation is critical for reestablishing totipotency in the zygote, but how histone-modifying enzymes are regulated during maternal reprogramming is not well characterized. To address this gap, we asked whether maternal reprogramming by the H3K4me1/2 demethylase SPR-5/LSD1/KDM1A, is regulated by the chromatin co-repressor protein, SPR-1/CoREST, in Caenorhabditis elegans and mice. In C. elegans, SPR-5 functions as part of a reprogramming switch together with the H3K9 methyltransferase MET-2. By examining germline development, fertility, and gene expression in double mutants between spr-1 and met-2, as well as fertility in double mutants between spr-1 and spr-5, we find that loss of SPR-1 results in a partial loss of SPR-5 maternal reprogramming function. In mice, we generated a separation of function Lsd1 M448V point mutation that compromises CoREST binding, but only slightly affects LSD1 demethylase activity. When maternal LSD1 in the oocyte is derived exclusively from this allele, the progeny phenocopy the increased perinatal lethality that we previously observed when LSD1 was reduced maternally. Together, these data are consistent with CoREST having a conserved function in facilitating maternal LSD1 epigenetic reprogramming.

Recent advances of LSD1/KDM1A inhibitors for disease therapy

Lysine-specific demethylase 1 (LSD1/KDM1A) dysregulation is closely associated with the pathological processes of various diseases, especially hematologic malignancies. Significant progresses have been made in the field of LSD1-targeted drug discovery. Nine LSD1 inhibitors including tranylcypromine, ORY-1001, ORY-2001, GSK-2879552, IMG-7289, INCB059872, TAK-418, CC-90011 and SP-2577 have entered clinical stage for disease treatment as either mono- or combinational therapy. This review updates LSD1 inhibitors reported during 2022. Design strategies, structure-activity relationship studies, binding model analysis and modes of action are highlighted. In particular, the unique multiple-copies binding mode of quinazoline derivatives paves new ways for the development of reversible LSD1 inhibitors by blocking the substrate entrance. The design strategy of clinical candidate TAK-418 also provides directions for further optimization of novel irreversible LSD1 inhibitors with low hematological side effects. The influence of the stereochemistry on the potency against LSD1 and its homolog LSD2 is briefly discussed. Finally, the challenges and prospects of LSD1-targeted drug discovery are also given.

Lysine-Specific Demethylase 1 (LSD1)-Mediated Epigenetic Modification of Immunogenicity and Immunomodulatory Effects in Breast Cancers

Tumor evolution to evade immune surveillance is a hallmark of carcinogenesis, and the modulation of tumor immunogenicity has been a challenge to present therapeutic responses in immunotherapies alone for numerous cancers. By altering the cell phenotype and reshaping the tumor microenvironment, epigenetic modifications enable tumor cells to overcome immune surveillance as a mechanism of cancer progression and immunotherapy resistance. Demethylase enzymatic activity of lysine-specific demethylase 1 (LSD1), a histone demethylase first identified in 2004, plays a pivotal role in the vast cellular processes of cancer. While FDA-approved indications for epigenetic therapies are limited to hematological malignancies, it is imperative to understand how epigenetic machinery can be targeted to prime immunotherapy responses in breast cancers. In this review, we discuss the potential roles of epigenetics and demethylating agent LSD1 as a potent new cancer management strategy to combat the current challenges of breast cancers, which have presented modest efficacy to immune checkpoint inhibitors till date. Additionally, we describe the combined use of LSD1-specific inhibitors and immune checkpoint inhibitors in existing breast cancer preclinical and clinical trials that elicits a robust immune response and benefit. Overall, the promising results observed in LSD1-targeting therapies signify the central role of epigenetics as a potential novel strategy to overcome resistance commonly seen in immunotherapies.

Structural and Functional Landscape of FAD-Dependent Histone Lysine Demethylases for New Drug Discovery

Small molecules targeting the flavin adenine dinucleotide (FAD)-dependent histone lysine demethylase LSD family have displayed therapeutic promise against various diseases. Nine clinical candidates targeting the classic demethylase-dependent functions of the LSD family are currently being investigated for treating cancers, neurodegenerative diseases, etc. Moreover, targeting noncatalytic functions of LSDs also represents an emerging strategy for treating human diseases. In this Perspective, we provide full structural and functional landscape of the LSD family and action modes of different types of LSD inhibitors including natural products, peptides, and synthetic compounds, aiming to reveal new druggable space for the design of new LSD inhibitors. Particularly, we first classify these inhibitors into three types based on their unique binding modes. Additionally, the strategies targeting the demethylase-independent functions of LSDs are also briefly discussed. This Perspective may benefit the discovery of new LSD inhibitors for probing LSD biology and/or treating human diseases.

Sequestration of cellular native factors by biomolecular assemblies: Physiological or pathological?

In addition to native-state structures, biomolecules often form condensed supramolecular assemblies or cellular membraneless organelles that are critical for cell life. These biomolecular assemblies, generally including liquid-like droplets (condensates) and amyloid-like aggregates, can sequester or recruit their interacting partners, so as to either modulate various cellular behaviors or even cause disorders. This review article summarizes recent advances in the sequestration of native factors by biomolecular assemblies and discusses their potential consequences on cellular function, homeostasis, and disease pathology.

Biological and therapeutic role of LSD1 in Alzheimer’s diseases

Alzheimer’s disease (AD) is a common chronic neurodegenerative disease characterized by cognitive learning and memory impairments, however, current treatments only provide symptomatic relief. Lysine-specific demethylase 1 (LSD1), regulating the homeostasis of histone methylation, plays an important role in the pathogenesis of many neurodegenerative disorders. LSD1 functions in regulating gene expression via transcriptional repression or activation, and is involved in initiation and progression of AD. Pharmacological inhibition of LSD1 has shown promising therapeutic benefits for AD treatment. In this review, we attempt to elaborate on the role of LSD1 in some aspects of AD including neuroinflammation, autophagy, neurotransmitters, ferroptosis, tau protein, as well as LSD1 inhibitors under clinical assessments for AD treatment.

Role of NAD+ and FAD in Ischemic Stroke Pathophysiology: An Epigenetic Nexus and Expanding Therapeutic Repertoire

The redox coenzymes viz., oxidized β-nicotinamide adenine dinucleotide (NAD⁺) and flavin adenine dinucleotide (FAD) by way of generation of optimal reducing power and cellular energy currency (ATP), control a staggering array of metabolic reactions. The prominent cellular contenders for NAD⁺ utilization, inter alia, are sirtuins (SIRTs) and poly(ADP-ribose) polymerase (PARP-1), which have been significantly implicated in ischemic stroke (IS) pathogenesis. NAD⁺ and FAD are also two crucial epigenetic enzyme-required metabolites mediating histone deacetylation and poly(ADP-ribosyl)ation through SIRTs and PARP-1 respectively, and demethylation through FAD-mediated lysine specific demethylase activity. These enzymes and post-translational modifications impinge on the components of neurovascular unit, primarily neurons, and elicit diverse functional upshots in an ischemic brain. These could be circumstantially linked with attendant cognitive deficits and behavioral outcomes in post-stroke epoch. Parsing out the contribution of NAD⁺/FAD-synthesizing and utilizing enzymes towards epigenetic remodeling in IS setting, together with their cognitive and behavioral associations, combined with possible therapeutic implications will form the crux of this review.

Lysine demethylase KDM1A promotes cell growth via FKBP8-BCL2 axis in hepatocellular carcinoma

Advanced hepatocellular carcinoma (HCC) has a dismal prognosis. KDM1A, overexpressed in multiple cancer types, is a lysine demethylase that targets both histone and non-histone proteins. However, it is unclear how KDM1A expression affects HCC etiology. Here, we show KDM1A can interact with and demethylate FKBP8, a cytoplasmic protein which regulates cell survival through the anti-apoptotic protein BCL2. We show demethylation of FKBP8 enhances its ability to stabilize BCL2. Consistently, we observed positive correlation between KDM1A and BCL2 protein levels in liver cancer patients. Functionally, we reveal FKBP8 demethylation by KDM1A is critical for liver cancer cell growth in vitro and in vivo. We went on to explore the mechanisms that might regulate KDM1A cytoplasmic localization. We found the cytoplasmic localization and protein stability of KDM1A was promoted by acetylation at Lysine-117 by the acetyl transferase KAT8. In agreement with this, we show KDM1A-K117 acetylation promotes demethylation of FKBP8 and level of BCL2. Finally, it has been shown that the efficacy of Sorafenib, a first-line treatment for advanced hepatocellular carcinoma, is limited by clinical resistance. We show KDM1A and BCL2 protein levels are increased during acquired sorafenib-resistance, while inhibiting KDM1A can antagonize sorafenib-resistance. Collectively, these results define a functional KDM1A-FKBP8-BCL2 axis in hepatocellular carcinoma.

Inter- and intra-chromosomal modulators of the APOE ɛ2 and ɛ4 effects on the Alzheimer's disease risk

The mechanisms of incomplete penetrance of risk-modifying impacts of apolipoprotein E (APOE) ε2 and ε4 alleles on Alzheimer's disease (AD) have not been fully understood. We performed genome-wide analysis of differences in linkage disequilibrium (LD) patterns between 6,136 AD-affected and 10,555 AD-unaffected subjects from five independent studies to explore whether the association of the APOE ε2 allele (encoded by rs7412 polymorphism) and ε4 allele (encoded by rs429358 polymorphism) with AD was modulated by autosomal polymorphisms. The LD analysis identified 24 (mostly inter-chromosomal) and 57 (primarily intra-chromosomal) autosomal polymorphisms with significant differences in LD with either rs7412 or rs429358, respectively, between AD-affected and AD-unaffected subjects, indicating their potential modulatory roles. Our Cox regression analysis showed that minor alleles of four inter-chromosomal and ten intra-chromosomal polymorphisms exerted significant modulating effects on the ε2- and ε4-associated AD risks, respectively, and identified ε2-independent (rs2884183 polymorphism, 11q22.3) and ε4-independent (rs483082 polymorphism, 19q13.32) associations with AD. Our functional analysis highlighted ε2- and/or ε4-linked processes affecting the lipid and lipoprotein metabolism and cell junction organization which may contribute to AD pathogenesis. These findings provide insights into the ε2- and ε4-associated mechanisms of AD pathogenesis, underlying their incomplete penetrance.

Relationship between Cognitive Dysfunction and Age-Related Variability in Oxidative Markers in Isolated Mitochondria of Alzheimer’s Disease Transgenic Mouse Brains

Many neurodegenerative disorders, including Alzheimer’s disease (AD), are strongly associated with the accumulation of oxidative damage. Transgenic animal models are commonly used to elucidate the pathogenic mechanism of AD. Beta amyloid (Aβ) and tau hyperphosphorylation are very famous hallmarks of AD and well-studied, but the relationship between mitochondrial dysfunction and the onset and progression of AD requires further elucidation. In this study we used transgenic mice (the strain name is 5xFAD) at three different ages (3, 6, and 20 months old) as an AD model. Cognitive impairment in AD mice occurred in an age-dependent manner. Aβ1-40 expression significantly increased in an age-dependent manner in all brain regions with or without AD, and Aβ1-42 expression in the hippocampus increased at a young age. In a Western blot analysis using isolated mitochondria from three brain regions (cerebral cortex, cerebellum, and hippocampus), NMNAT-3 expression in the hippocampi of aged AD mice was significantly lower than that of young AD mice. SOD-2 expression in the hippocampi of AD mice was lower than for the age-matched controls. However, 3-NT expression in the hippocampi of AD mice was higher than for the age-matched controls. NQO-1 expression in the cerebral cortex of AD mice was higher than for the age-matched controls at every age that we examined. However, hippocampal NQO-1 expression in 6-month-old AD mice was significantly lower than in 3-month-old AD mice. These results indicate that oxidative stress in the hippocampi of AD mice is high compared to other brain regions and may induce mitochondrial dysfunction via oxidative damage. Protection of mitochondria from oxidative damage may be important to maintain cognitive function.

Altered succinylation of mitochondrial proteins, APP and tau in Alzheimer's disease

Abnormalities in brain glucose metabolism and accumulation of abnormal protein deposits called plaques and tangles are neuropathological hallmarks of Alzheimer's disease (AD), but their relationship to disease pathogenesis and to each other remains unclear. Here we show that succinylation, a metabolism-associated post-translational protein modification (PTM), provides a potential link between abnormal metabolism and AD pathology. We quantified the lysine succinylomes and proteomes from brains of individuals with AD, and healthy controls. In AD, succinylation of multiple mitochondrial proteins declined, and succinylation of small number of cytosolic proteins increased. The largest increases occurred at critical sites of amyloid precursor protein (APP) and microtubule-associated tau. We show that in vitro, succinylation of APP disrupted its normal proteolytic processing thereby promoting Aβ accumulation and plaque formation and that succinylation of tau promoted its aggregation to tangles and impaired microtubule assembly. In transgenic mouse models of AD, elevated succinylation associated with soluble and insoluble APP derivatives and tau. These findings indicate that a metabolism-linked PTM may be associated with AD.

A putative role for lncRNAs in epigenetic regulation of memory

The central dogma of molecular genetics is defined as encoded genetic information within DNA, transcribed into messenger RNA, which contain the instructions for protein synthesis, thus imparting cellular functionality and ultimately life. This molecular genetic theory has given birth to the field of neuroepigenetics, and it is now well established that epigenetic regulation of gene transcription is critical to the learning and memory process. In this review, we address a potential role for a relatively new player in the field of epigenetic crosstalk - long non-coding RNAs (lncRNAs). First, we briefly summarize epigenetic mechanisms in memory formation and examine what little is known about the emerging role of lncRNAs during this process. We then focus discussions on how lncRNAs interact with epigenetic mechanisms to control transcriptional programs under various conditions in the brain, and how this may be applied to regulation of gene expression necessary for memory formation. Next, we explore how epigenetic crosstalk in turn serves to regulate expression of various individual lncRNAs themselves. To highlight the importance of further exploring the role of lncRNA in epigenetic regulation of gene expression, we consider the significant relationship between lncRNA dysregulation and declining memory reserve with aging, Alzheimer's disease, and epilepsy, as well as the promise of novel therapeutic interventions. Finally, we conclude with a discussion of the critical questions that remain to be answered regarding a role for lncRNA in memory.

Therapeutic potential of targeting LSD1/ KDM1A in cancers

LSD1 was the first histone demethylase identified by Professor Shi Yang and his team members in 2004. LSD1 employs FAD as its cofactor, which catalyzes the demethylation of H3K4 and H3K9. It is aberrantly overexpressed in different types of cancers and is associated with the growth, invasion, and metastasis of cancer cells. The knockout or inhibition of LSD1 could effectively suppress tumor development, and thus, it has become an attractive molecular target for cancer therapy. Moreover, many LSD1 inhibitors have been developed in preclinical and clinical trials to treat solid tumors and hematological malignancy. This study made an extensive review of the research obtained from the literature retrieval of electronic databases, such as PubMed, Web of Science, RCSB PDB, ClinicalTrials.gov, and EU clinical trials register. This review summarizes recent studies on the advances of LSD1 inhibitors in the literature, covering January 2015 to June 2021. It focuses on the function of LSD1 in tumor cells, summarizes the crystal structures of homo sapiens LSD1, reviews the structural characteristics of LSD1 inhibitors, compares the screening methods of LSD1 inhibitors, and proposes guidelines for the future exploitation of LSD1 inhibitors.

Roles of lysine-specific demethylase 1 (LSD1) in homeostasis and diseases

Lysine-specific demethylase 1 (LSD1) targets mono- or di-methylated histone H3K4 and H3K9 as well as non-histone substrates and functions in the regulation of gene expression as a transcriptional repressor or activator. This enzyme plays a pivotal role in various physiological processes, including development, differentiation, inflammation, thermogenesis, neuronal and cerebral physiology, and the maintenance of stemness in stem cells. LSD1 also participates in pathological processes, including cancer as the most representative disease. It promotes oncogenesis by facilitating the survival of cancer cells and by generating a pro-cancer microenvironment. In this review, we discuss the role of LSD1 in several aspects of cancer, such as hypoxia, epithelial-to-mesenchymal transition, stemness versus differentiation of cancer stem cells, as well as anti-tumor immunity. Additionally, the current understanding of the involvement of LSD1 in various other pathological processes is discussed.