HIV Promotes NLRP3 Inflammasome Complex Activation in Murine HIV-Associated Nephropathy

Targeting inflammasomes as a therapeutic potential for HIV/AIDS

Human immunodeficiency virus (HIV) infection in humans can cause a variety of symptoms. Among these, acquired immunodeficiency syndrome (AIDS) remains the most severe form. Current treatment of HIV/AIDS with antiretroviral drugs effectively inhibits HIV replication and infection and significantly extends the lifespan of HIV/AIDS patients. However, antiretroviral drugs cannot completely remove HIV from patients due to the high latency of HIV, and they possess side effects and can lead to drug resistance. HIV/AIDS remains to be an incurable disease, and new methods and drugs are still desirable. Inflammasomes were found to be activated during HIV infection and regulate AIDS progression. Previous reviews provide a simple summary of inflammasome activators and inhibitors during HIV infection without distinguishing the specific infection stage, this kind of summary does not provide any clinical target value. Here, we provide a comprehensive review of inflammasomes in HIV/AIDS according to the infection timeline and propose several inflammasome target strategies for clinical HIV/AIDS treatment. We systematacially summarized the activation and function of kinds inflammasomes during the different HIV infection stages, with the aim of providing new therapeutic targets and directions for HIV/AIDS and HIV-associated comorbidities.

The Interplay Between Viral Infection and Cell Death: A Ping-Pong Effect

Programmed cell death (PCD) is a well-studied cellular mechanism that plays a critical role in immune responses, developmental processes, and the maintenance of tissue homeostasis. However, viruses have developed diverse strategies to bypass or manipulate the host apoptotic machinery to enhance their replication and survival. As a result, the interaction between PCD pathways and viruses has garnered increased interest, leading to many studies being published in recent years. This study aims to provide an overview of the current understanding of PCD pathways and their significance in viral infections. We will discuss various forms of cell death pathways, including apoptosis, autophagy, necroptosis, and pyroptosis, as well as their corresponding molecular mechanisms. In addition, we will show how viruses manipulate host PCD pathways to prevent or delay cell death or facilitate viral replication. This study emphasizes the importance of investigating the mechanisms by which viruses control the host's PCD machinery to gain insight into the evolutionary dynamics of host-pathogen interactions and to develop new approaches for predicting and managing viral threats. Overall, we aimed to highlight new research areas in PCD and viruses, including introduction of new targets for the development of new antiviral drugs to modulate the cellular apoptotic machinery and novel inhibitors of host cell death pathways.

Inflammasomes and idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are a group of systemic autoimmune diseases characterized by muscle weakness and elevated serum creatine kinase levels. Recent research has highlighted the role of the innate immune system, particularly inflammasomes, in the pathogenesis of IIM. This review focuses on the role of inflammasomes, specifically NLRP3 and AIM2, and their associated proteins in the development of IIM. We discuss the molecular mechanisms of pyroptosis, a programmed cell death pathway that triggers inflammation, and its association with IIM. The NLRP3 inflammasome, in particular, has been implicated in muscle fiber necrosis and the subsequent release of damage-associated molecular patterns (DAMPs), leading to inflammation. We also explore the potential therapeutic implications of targeting the NLRP3 inflammasome with inhibitors such as glyburide and MCC950, which have shown promise in reducing inflammation and improving muscle function in preclinical models. Additionally, we discuss the role of caspases, particularly caspase-1, in the canonical pyroptotic pathway associated with IIM. The understanding of these mechanisms offers new avenues for therapeutic intervention and a better comprehension of IIM pathophysiology.

PKR activation-induced mitochondrial dysfunction in HIV-transgenic mice with nephropathy

HIV disease remains prevalent in the USA and chronic kidney disease remains a major cause of morbidity in HIV-1-positive patients. Host double-stranded RNA (dsRNA)-activated protein kinase (PKR) is a sensor for viral dsRNA, including HIV-1. We show that PKR inhibition by compound C16 ameliorates the HIV-associated nephropathy (HIVAN) kidney phenotype in the Tg26 transgenic mouse model, with reversal of mitochondrial dysfunction. Combined analysis of single-nucleus RNA-seq and bulk RNA-seq data revealed that oxidative phosphorylation was one of the most downregulated pathways and identified signal transducer and activator of transcription (STAT3) as a potential mediating factor. We identified in Tg26 mice a novel proximal tubular cell cluster enriched in mitochondrial transcripts. Podocytes showed high levels of HIV-1 gene expression and dysregulation of cytoskeleton-related genes, and these cells dedifferentiated. In injured proximal tubules, cell-cell interaction analysis indicated activation of the pro-fibrogenic PKR-STAT3-platelet-derived growth factor (PDGF)-D pathway. These findings suggest that PKR inhibition and mitochondrial rescue are potential novel therapeutic approaches for HIVAN.

Tmem30a protects against podocyte injury through suppression of pyroptosis

Podocytopathies, such as focal segmental glomerulosclerosis (FSGS), are characterized by podocyte injury and can easily progress to end-stage kidney disease. However, the mechanisms underlying podocyte injury remain unclear. We observed podocyte injury along with pyroptosis in patients with FSGS. Bioinformatic analysis of public datasets revealed that transmembrane protein 30a (Tmem30a) might be associated with FSGS. The expression of Temem30a and the podocyte-related protein, nephrin, were significantly downregulated in patients with FSGS, adriamycin (ADR)-induced mice, and podocyte-specific Tmem30a lox P /loxP ; NPHS2-Cre mice, whereas the expression of NLR family pyrin domain containing 3 (NLRP3) and ASC, two pyroptosis-related proteins, were significantly upregulated. Meanwhile, the pyroptosis inhibitor MCC950 and disulfiram (DSF) increased Tmem30a and podocyte-related proteins expression, and inhibited pyroptosis-related proteins expression in ADR-induced mouse podocytes and Tmem30a knockdown (KD) mouse podocytes. Therefore, Tmem30a might protect against podocyte injury by inhibiting pyroptosis, suggesting a potential therapeutic target for podocytopathies.

The Role of Pyroptosis in the Pathogenesis of Kidney Diseases

BACKGROUND

Recently, in addition to apoptosis and necrosis, several other forms of cell death have been discovered, such as necroptosis, autophagy, pyroptosis, and ferroptosis. These cell death modalities play diverse roles in kidney diseases. Pyroptosis is a newly described type of proinflammatory programmed necrosis. Further exploring pyroptosis is helpful to slow the progression of kidney diseases and reduce their complications.

SUMMARY

Pyroptosis is mainly mediated by the cleavage of gasdermin D (GSDMD) along with downstream inflammasome activation. Activated caspase-1 induces the release of cytokines by cleaving GSDMD. Inflammation is a major pathogenic mechanism for kidney diseases. Increasing evidence corroborated that pyroptosis was closely related to the progression of renal diseases, including acute kidney injury, renal fibrosis, diabetic nephropathy, and kidney cancer. In this paper, we reviewed the role and the therapeutic treatment of pyroptosis in renal diseases.

KEY MESSAGES

The better understanding of the progress and new intervention approaches of pyroptosis in kidney diseases may pave the way for new therapeutic opportunities in clinical practice.

Toxoplasma gondii Induces Pyroptosis in Human Placental Trophoblast and Amniotic Cells by Inducing ROS Production and Activation of Cathepsin B and NLRP1/NLRP3/NLRC4/AIM2 Inflammasome

Toxoplasma gondii infection in pregnant women may cause fetal anomalies; however, the underlying mechanisms remain unclear. The current study investigated whether T. gondii induces pyroptosis in human placental cells and the underlying mechanisms. Human placental trophoblast (BeWo and HTR-8/SVneo) and amniotic (WISH) cells were infected with T. gondii, and then reactive oxygen species (ROS) production, cathepsin B (CatB) release, inflammasome activation, and pyroptosis induction were evaluated. The molecular mechanisms of these effects were investigated by treating the cells with ROS scavengers, a CatB inhibitor, or inflammasome-specific siRNA. T. gondii infection induced ROS generation and CatB release into the cytosol in placental cells but decreased mitochondrial membrane potential. T. gondii-infected human placental cells and villi exhibited NLRP1, NLRP3, NLRC4, and AIM2 inflammasome activation and subsequent pyroptosis induction, as evidenced by increased expression of ASC, cleaved caspase-1, and mature IL-1β and gasdermin D cleavage. In addition to inflammasome activation and pyroptosis induction, adverse pregnancy outcome was shown in a T. gondii-infected pregnant mouse model. Administration of ROS scavengers, CatB inhibitor, or inflammasome-specific siRNA into T. gondii-infected cells reversed these effects. Collectively, these findings show that T. gondii induces NLRP1/NLRP3/NLRC4/AIM2 inflammasome-dependent caspase-1-mediated pyroptosis via induction of ROS production and CatB activation in placental cells. This mechanism may play an important role in inducing cell injury in congenital toxoplasmosis.

Research progress on multiple cell death pathways of podocytes in diabetic kidney disease

Diabetic kidney disease (DKD) is the main cause of end-stage renal disease, and its clinical manifestations are progressive proteinuria, decreased glomerular filtration rate, and renal failure. The injury and death of glomerular podocytes are the keys to DKD. Currently, a variety of cell death modes have been identified in podocytes, including apoptosis, autophagy, endoplasmic reticulum (ER) stress, pyroptosis, necroptosis, ferroptosis, mitotic catastrophe, etc. The signaling pathways leading to these cell death processes are interconnected and can be activated simultaneously or in parallel. They are essential for cell survival and death that determine the fate of cells. With the deepening of the research on the mechanism of cell death, more and more researchers have devoted their attention to the underlying pathologic research and the drug therapy research of DKD. In this paper, we discussed the podocyte physiologic role and DKD processes. We also provide an overview of the types and specific mechanisms involved in each type of cell death in DKD, as well as related targeted therapy methods and drugs are reviewed. In the last part we discuss the complexity and potential crosstalk between various modes of cell death, which will help improve the understanding of podocyte death and lay a foundation for new and ideal targeted therapy strategies for DKD treatment in the future.

HIV-1 activates oxidative phosphorylation in infected CD4 T cells in a human tonsil explant model

Introduction

Human immunodeficiency virus type 1 (HIV-1) causes a chronic, incurable infection leading to immune activation and chronic inflammation in people with HIV-1 (PWH), even with virologic suppression on antiretroviral therapy (ART). The role of lymphoid structures as reservoirs for viral latency and immune activation has been implicated in chronic inflammation mechanisms. Still, the specific transcriptomic changes induced by HIV-1 infection in different cell types within lymphoid tissue remain unexplored.

Methods

In this study, we utilized human tonsil explants from healthy human donors and infected them with HIV-1 ex vivo. We performed single-cell RNA sequencing (scRNA-seq) to analyze the cell types represented in the tissue and to investigate the impact of infection on gene expression profiles and inflammatory signaling pathways.

Results

Our analysis revealed that infected CD4+ T cells exhibited upregulation of genes associated with oxidative phosphorylation. Furthermore, macrophages exposed to the virus but uninfected showed increased expression of genes associated with the NLRP3 inflammasome pathway.

Discussion

These findings provide valuable insights into the specific transcriptomic changes induced by HIV-1 infection in different cell types within lymphoid tissue. The activation of oxidative phosphorylation in infected CD4+ T cells and the proinflammatory response in macrophages may contribute to the chronic inflammation observed in PWH despite ART. Understanding these mechanisms is crucial for developing targeted therapeutic strategies to eradicate HIV-1 infection in PWH.

The Impact of COVID-19 on People Living with HIV-1 and HIV-1-Associated Neurological Complications

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative pathogen of the coronavirus disease 2019 (COVID-19) pandemic, a fatal respiratory illness. The associated risk factors for COVID-19 are old age and medical comorbidities. In the current combined antiretroviral therapy (cART) era, a significant portion of people living with HIV-1 (PLWH) with controlled viremia is older and with comorbidities, making these people vulnerable to SARS-CoV-2 infection and COVID-19-associated severe outcomes. Additionally, SARS-CoV-2 is neurotropic and causes neurological complications, resulting in a health burden and an adverse impact on PLWH and exacerbating HIV-1-associated neurocognitive disorder (HAND). The impact of SARS-CoV-2 infection and COVID-19 severity on neuroinflammation, the development of HAND and preexisting HAND is poorly explored. In the present review, we compiled the current knowledge of differences and similarities between SARS-CoV-2 and HIV-1, the conditions of the SARS-CoV-2/COVID-19 and HIV-1/AIDS syndemic and their impact on the central nervous system (CNS). Risk factors of COVID-19 on PLWH and neurological manifestations, inflammatory mechanisms leading to the neurological syndrome, the development of HAND, and its influence on preexisting HAND are also discussed. Finally, we have reviewed the challenges of the present syndemic on the world population, with a particular emphasis on PLWH.

Inflammation and oxidative stress in salt sensitive hypertension; The role of the NLRP3 inflammasome

Salt-sensitivity of blood pressure is an independent risk factor for cardiovascular disease and affects approximately half of the hypertensive population. While the precise mechanisms of salt-sensitivity remain unclear, recent findings on body sodium homeostasis and salt-induced immune cell activation provide new insights into the relationship between high salt intake, inflammation, and hypertension. The immune system, specifically antigen-presenting cells (APCs) and T cells, are directly implicated in salt-induced renal and vascular injury and hypertension. Emerging evidence suggests that oxidative stress and activation of the NLRP3 inflammasome drive high sodium-mediated activation of APCs and T cells and contribute to the development of renal and vascular inflammation and hypertension. In this review, we summarize the recent insights into our understanding of the mechanisms of salt-sensitive hypertension and discuss the role of inflammasome activation as a potential therapeutic target.

NLRP3-mediated pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN) is the main cause of end-stage renal disease (ESRD), which is characterized by a series of abnormal changes such as glomerulosclerosis, podocyte loss, renal tubular atrophy and excessive deposition of extracellular matrix. Simultaneously, the occurrence of inflammatory reaction can promote the aggravation of DN-induced kidney injury. The most important processes in the canonical inflammasome pathway are inflammasome activation and membrane pore formation mediated by gasdermin family. Converging studies shows that pyroptosis can occur in renal intrinsic cells and participate in the development of DN, and its activation mechanism involves a variety of signaling pathways. Meanwhile, the activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome can not only lead to the occurrence of inflammatory response, but also induce pyroptosis. In addition, a number of drugs targeting pyroptosis-associated proteins have been shown to have potential for treating DN. Consequently, the pathogenesis of pyroptosis and several possible activation pathways of NLRP3 inflammasome were reviewed, and the potential drugs used to treat pyroptosis in DN were summarized in this review. Although relevant studies are still not thorough and comprehensive, these findings still have certain reference value for the understanding, treatment and prognosis of DN.

Multi-Target Effects of ß-Caryophyllene and Carnosic Acid at the Crossroads of Mitochondrial Dysfunction and Neurodegeneration: From Oxidative Stress to Microglia-Mediated Neuroinflammation

Inflammation and oxidative stress are interlinked and interdependent processes involved in many chronic diseases, including neurodegeneration, diabetes, cardiovascular diseases, and cancer. Therefore, targeting inflammatory pathways may represent a potential therapeutic strategy. Emerging evidence indicates that many phytochemicals extracted from edible plants have the potential to ameliorate the disease phenotypes. In this scenario, ß-caryophyllene (BCP), a bicyclic sesquiterpene, and carnosic acid (CA), an ortho-diphenolic diterpene, were demonstrated to exhibit anti-inflammatory, and antioxidant activities, as well as neuroprotective and mitoprotective effects in different in vitro and in vivo models. BCP essentially promotes its effects by acting as a selective agonist and allosteric modulator of cannabinoid type-2 receptor (CB2R). CA is a pro-electrophilic compound that, in response to oxidation, is converted to its electrophilic form. This can interact and activate the Keap1/Nrf2/ARE transcription pathway, triggering the synthesis of endogenous antioxidant “phase 2” enzymes. However, given the nature of its chemical structure, CA also exhibits direct antioxidant effects. BCP and CA can readily cross the BBB and accumulate in brain regions, giving rise to neuroprotective effects by preventing mitochondrial dysfunction and inhibiting activated microglia, substantially through the activation of pro-survival signalling pathways, including regulation of apoptosis and autophagy, and molecular mechanisms related to mitochondrial quality control. Findings from different in vitro/in vivo experimental models of Parkinson’s disease and Alzheimer’s disease reported the beneficial effects of both compounds, suggesting that their use in treatments may be a promising strategy in the management of neurodegenerative diseases aimed at maintaining mitochondrial homeostasis and ameliorating glia-mediated neuroinflammation.

Cell pyroptosis in picornavirus and its potential for treating viral infection

Cell pyroptosis has received increased attention due to the associations between innate immunity and disease, and it has become a major focal point recently due to in-depth studies of cancer. With increased research on pyroptosis, scientists have discovered that it has an essential role in viral infections, especially in the occurrence and development of some picornavirus infections. Many picornaviruses, including Coxsackievirus, a71 enterovirus, human rhinovirus, encephalomyocarditis virus, and foot-and-mouth disease virus induce pyroptosis to varying degrees. This review summarized the mechanisms by which these viruses induce cell pyroptosis, which can be an effective defense against pathogen infection. However, excessive inflammasome activation or pyroptosis also can damage the host's health or aggravate disease progression. Careful approaches that acknowledge this dual effect will aid in the exploration of picornavirus infections and the mechanisms that produce the inflammatory response. This information will promote the development of drugs that can inhibit cell pyroptosis and provide new avenues for future clinical treatment. This article is protected by copyright. All rights reserved.

Novel insights into NOD-like receptors in renal diseases

Nucleotide-binding oligomerization domain-like receptors (NLRs), including NLRAs, NLRBs (also known as NAIPs), NLRCs, and NLRPs, are a major subfamily of pattern recognition receptors (PRRs). Owing to a recent surge in research, NLRs have gained considerable attention due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, which is a central phenomenon in the pathogenesis of multiple diseases, including renal diseases. NLRs are expressed in different renal tissues during pathological conditions, which suggest that these receptors play roles in acute kidney injury, obstructive nephropathy, diabetic nephropathy, IgA nephropathy, lupus nephritis, crystal nephropathy, uric acid nephropathy, and renal cell carcinoma, among others. This review summarises recent progress on the functions of NLRs and their mechanisms in the pathophysiological processes of different types of renal diseases to help us better understand the role of NLRs in the kidney and provide a theoretical basis for NLR-targeted therapy for renal diseases.

Complement induces podocyte pyroptosis in membranous nephropathy by mediating mitochondrial dysfunction

Podocyte damage mediated by in situ complement activation in the glomeruli is a key factor in the pathogenesis of membranous nephropathy (MN), but the molecular mechanism has not been fully elucidated. Pyroptosis is a special type of programmed cell death, mediate inflammatory response and induce tissue injury. However, it is not clear whether pyroptosis is involved in the development and progression of MN. Here, we report that pyroptosis plays an important role in promoting podocyte injury in MN. We first observed the occurrence of pyroptosis in the kidneys of MN patients and validated that complement stimulation triggered pyroptosis in podocytes and that inhibiting pyroptosis reversed complement-induced podocyte damage in vitro. In addition, stimulation of complement caused mitochondrial depolarization and reactive oxygen species (ROS) production in podocytes, and inhibition of ROS reversed complement-induced pyroptosis in podocytes. Interestingly, inhibition of pyroptosis in turn partially alleviated these effects. Furthermore, we also found the involvement of pyroptosis in the kidneys of passive Heymann nephritis (PHN) rats, and inhibitors of pyroptosis-related molecules relieved PHN-induced kidney damage in vivo. Our findings demonstrate that pyroptosis plays a critical role in complement-induced podocyte damage in MN and mitochondrial dysfunction is an important mechanism underlying this process. It provides new insight that pyroptosis may serve as a novel therapeutic target for MN treatment in future studies.

Role of inflammasomes in HIV-1 infection and treatment

Although combined antiretroviral therapy (cART) is effective in inhibiting human immunodeficiency virus type 1 (HIV-1) replication, it does not eradicate the virus because small amounts of latent HIV-1 provirus persist in quiescent memory CD4⁺ T cells. Therefore, strategies for eradicating latent HIV-1 are urgently needed. Recently, several studies have reported that the inflammatory response and lymphocyte death induced by HIV-1 depend on inflammasomes and pyroptosis, suggesting that inflammasomes and pyroptosis have a vital role in HIV-1 infection and contribute to the eradication of latent HIV-1. In this review, we summarize current knowledge of the role of inflammasomes, including NLR family pyrin domain-containing protein 3 (NLRP3), caspase recruitment domain-containing protein 8 (CARD8), interferon-inducible protein 16 (IFI16), NLRP1, NLR family CARD domain-containing 4 (NLRC4), and absent in melanoma 2 (AIM2), in HIV-1 infection and discuss promising therapeutic strategies for HIV-1-associated diseases by targeting inflammasomes.

Mitochondrial Oxidative Stress and Cell Death in Podocytopathies

Podocytopathies are kidney diseases that are driven by podocyte injury with proteinuria and proteinuria-related symptoms as the main clinical presentations. Albeit podocytopathies are the major contributors to end-stage kidney disease, the underlying molecular mechanisms of podocyte injury remain to be elucidated. Mitochondrial oxidative stress is associated with kidney diseases, and increasing evidence suggests that oxidative stress plays a vital role in the pathogenesis of podocytopathies. Accumulating evidence has placed mitochondrial oxidative stress in the focus of cell death research. Excessive generated reactive oxygen species over antioxidant defense under pathological conditions lead to oxidative damage to cellular components and regulate cell death in the podocyte. Conversely, exogenous antioxidants can protect podocyte from cell death. This review provides an overview of the role of mitochondrial oxidative stress in podocytopathies and discusses its role in the cell death of the podocyte, aiming to identify the novel targets to improve the treatment of patients with podocytopathies.

Effect of genipin-1-β-d-gentiobioside on diabetic nephropathy in mice by activating AMP-activated protein kinase/silencing information regulator-related enzyme 1/ nuclear factor-κB pathway

OBJECTIVES

Genipin-1-β-d-gentiobioside (GG) is a kind of compound extracted from Gardenia jasminoides Ellis. The chemical structure of GG is similar to that of geniposide and has antidiabetic effects. We aimed to investigate the efficacy of GG on diabetic nephropathy (DN) in vivo and in vitro experiments and explore its potential mechanism.

METHODS

For high-fat diet/streptozotocin-induced DN mice used in our study, the general features of mice were analysed after GG treatment. Oxidative stress parameters and inflammatory factors were also measured by commercial kits. Kidney damage was assessed using hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) and Masson staining, respectively. In vitro, podocyte injury was assessed by TUNEL and flow cytometric analyses. AMP-activated protein kinase/silencing information regulator related enzyme 1 (AMPK/SIRT1)/nuclear factor-κB (NF-κB) pathway-related proteins were detected by AMPK-siRNA intervention and western blotting.

KEY FINDINGS

Treatment of GG could increase cell survival and attenuated kidney damage. Despite the presence of inflammatory and oxidative stress, when GG retained the expression of AMPK/SIRT1, it could be observed that the downstream NLRP3 inflammatory-related proteins were inhibited.

CONCLUSIONS

Results showed that the protective efficacy of GG on DN works together with hypoglycemia and suppressing oxidative stress and inflammation, which at least partly involved in APMK/SIRT1/NF-κB-dependent pathway.

Pyroptosis and Redox Balance in Kidney Diseases

Significance: Kidney diseases remain a worldwide public health problem resulting in millions of deaths each year; they are characterized by progressive destruction of renal function by sustained inflammation. Pyroptosis is a lytic type of programmed cell death involved in inflammation, as well as a key fibrotic mechanism that is critical in the development of kidney pathology. Pyroptosis is induced by the cleavage of Gasdermins by various caspases and is executed by the insertion of the N-terminal fragment of cleaved Gasdermins into the plasma membrane, creating oligomeric pores and allowing the release of diverse proinflammatory products into the extracellular space. Inflammasomes are multiprotein complexes leading to the activation of caspase-1, which will cleave Gasdermin D, releasing several proinflammatory cytokines; this results in the initiation and amplification of the inflammatory response. Recent Advances: The efficacy of Gasdermin D cleavage is reduced by a change in the redox balance. Recently, several studies have shown that the attenuation of reactive oxygen species (ROS) production induced by antioxidant pathways results in a reduction of renal pyroptosis. In this review, we discuss the role of pyroptosis in the pathogenesis of chronic kidney disease (CKD) and acute kidney disease; summarize the clinical outcomes and different molecular mechanisms leading to Gasdermin activation; and examine studies about the capacity of antioxidants, particularly Nrf2 activators, to ameliorate Gasdermin activity. Future Directions: We illustrate the potential influence of the deregulation of redox balance on inflammasome activity and pyroptosis as a novel therapeutic approach for the treatment of kidney diseases. Antioxid. Redox Signal. 35, 40-60.

Caspase-1-Inhibitor AC-YVAD-CMK Inhibits Pyroptosis and Ameliorates Acute Kidney Injury in a Model of Sepsis

Objective

To observe the protective effect of AC-YVAD-CMK on sepsis-induced acute kidney injury in mice and to explore its possible mechanisms primarily.

Methods

Eighteen male C57BL/6 mice were randomly divided into sham-operated group (Control), cecal ligation and puncture group (CLP), and CLP model treated with AC-YVAD-CMK group (AC-YVAD-CMK) (n = 6 in each group). Mice were sacrificed at 24 h after operation, and blood and kidney tissue samples were collected for analyses. Histologic changes were determined microscopically following HE staining. The expression of Ly-6B and CD68 was investigated using immunohistochemistry. Serum concentrations of creatinine (sCR) and blood urea nitrogen (BUN) were measured. Serum levels of interleukin-1β (IL-1β), interleukin-18 (IL-18), TNF-α, and interleukin-6 (IL-6) were determined by ELISA. The expressions of Caspas-1, NLRP-1, IL-1β, and IL-18 in renal tissues were investigated using Western blot. Immunofluorescence staining was used to detect the expression of GSDMD protein in renal tissues.

Results

AC-YVAD-CMK treatment significantly alleviates sepsis-induced acute kidney injury, with decreased histological injury in renal tissues, suppresses the accumulation of neutrophils and macrophages in renal tissues, and decreased sCR and BUN level (P < 0.05). Attenuation of sepsis-induced acute kidney injury was due to the prohibited production of inflammatory cytokines and decrease expression of Caspas-1, NLRP-1, IL-1β, and IL-18 in renal tissues. In addition, AC-YVAD-CMK treatment significantly reduced the expression of GSDMD in renal tissues compared to those observed in controls (P < 0.05).

Conclusions

We demonstrated a marked renoprotective effect of caspase-1-inhibitor AC-YVAD-CMK in a rat model of sepsis by inhibition of pyroptosis.

Pyroptosis: A New Frontier in Kidney Diseases

Pyroptosis is a pattern of programmed cell death that significantly differs from apoptosis and autophagy in terms of cell morphology and function. The process of pyroptosis is characterized predominantly by the formation of gasdermin protein family-mediated membrane perforation, cell collapse, and the release of inflammatory factors, including IL-1β and IL-18. In recent years, with the rise of pyroptosis research, scholars have devoted time to study the mechanism of pyroptosis in kidney-related diseases. Pyroptosis is probably involved in kidney diseases through two pathways: the caspase-1-mediated canonical pathway and the caspase-4/5/11-mediated noncanonical pathway. In addition, some scholars have identified targets for the treatment of kidney-related diseases from the viewpoint of pyroptosis and developed corresponding medicines, which may become a recommendation for prognosis, targeted treatment, and clinical diagnosis of kidney diseases. This paper focuses on the up-to-date advances in the field of pyroptosis, especially on the key pathogenic role of pyroptosis in the development and progression of kidney diseases. It presents a more in-depth understanding of the pathogenesis of kidney diseases and introduces novel therapeutic targets for the prevention and clinical treatment of kidney diseases.

Thyroid Hormones Interaction With Immune Response, Inflammation and Non-thyroidal Illness Syndrome

The interdependence between thyroid hormones (THs), namely, thyroxine and triiodothyronine, and immune system is nowadays well-recognized, although not yet fully explored. Synthesis, conversion to a bioactive form, and release of THs in the circulation are events tightly supervised by the hypothalamic-pituitary-thyroid (HPT) axis. Newly synthesized THs induce leukocyte proliferation, migration, release of cytokines, and antibody production, triggering an immune response against either sterile or microbial insults. However, chronic patho-physiological alterations of the immune system, such as infection and inflammation, affect HPT axis and, as a direct consequence, THs mechanism of action. Herein, we revise the bidirectional crosstalk between THs and immune cells, required for the proper immune system feedback response among diverse circumstances. Available circulating THs do traffic in two distinct ways depending on the metabolic condition. Mechanistically, internalized THs form a stable complex with their specific receptors, which, upon direct or indirect binding to DNA, triggers a genomic response by activating transcriptional factors, such as those belonging to the Wnt/β-catenin pathway. Alternatively, THs engage integrin αvβ3 receptor on cell membrane and trigger a non-genomic response, which can also signal to the nucleus. In addition, we highlight THs-dependent inflammasome complex modulation and describe new crucial pathways involved in microRNA regulation by THs, in physiological and patho-physiological conditions, which modify the HPT axis and THs performances. Finally, we focus on the non-thyroidal illness syndrome in which the HPT axis is altered and, in turn, affects circulating levels of active THs as reported in viral infections, particularly in immunocompromised patients infected with human immunodeficiency virus.

Emerging Role of the Inflammasome and Pyroptosis in Hypertension

Inflammasomes are components of the innate immune response that have recently emerged as crucial controllers of tissue homeostasis. In particular, the nucleotide-binding domain, leucine-rich-containing (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a complex platform involved in the activation of caspase-1 and the maturation of interleukin (IL)-1β and IL-18, which are mainly released via pyroptosis. Pyroptosis is a caspase-1-dependent type of cell death that is mediated by the cleavage of gasdermin D and the subsequent formation of structurally stable pores in the cell membrane. Through these pores formed by gasdermin proteins cytosolic contents are released into the extracellular space and act as damage-associated molecular patterns, which are pro-inflammatory signals. Inflammation is a main contributor to the development of hypertension and it also is known to stimulate fibrosis and end-organ damage. Patients with essential hypertension and animal models of hypertension exhibit elevated levels of circulating IL-1β. Downregulation of the expression of key components of the NLRP3 inflammasome delays the development of hypertension and pharmacological inhibition of this inflammasome leads to reduced blood pressure in animal models and humans. Although the relationship between pyroptosis and hypertension is not well established yet, pyroptosis has been associated with renal and cardiovascular diseases, instances where high blood pressure is a critical risk factor. In this review, we summarize the recent literature addressing the role of pyroptosis and the inflammasome in the development of hypertension and discuss the potential use of approaches targeting this pathway as future anti-hypertensive strategies.

APOL1 risk variants and the development of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) remains a concern among untreated HIV patients, notably of African descent, as patients can reach end-stage renal disease within 3 years. Two variants (G1 and G2) of the APOL1 gene, common in African populations to protect against African sleeping sickness, have been associated with an increased risk of several glomerular disorders including HIVAN, hypertension-attributed chronic kidney disease, and idiopathic focal segmental glomerulosclerosis and are accordingly named renal risk variants (RRVs). This review examines the mechanisms by which APOL1 RRVs drive glomerular injury in the setting of HIV infection and their potential application to patient management. Innate antiviral mechanisms activated by chronic HIV infection, especially those involving type 1 interferons, are of particular interest as they have been shown to upregulate APOL1 expression. Additionally, the downregulation of miRNA 193a (a repressor of APOL1) is also associated with the upregulation of APOL1. Interestingly, glomerular damage affected by APOL1 RRVs is caused by both loss- and gain-of-function changes in the protein, explicitly characterizing these effects. Their intracellular localization offers a further understanding of the nuances of APOL1 variant effects in promoting renal disease. Finally, although APOL1 variants have been recognized as a critical genetic player in mediating kidney disease, there are significant gaps in their application to patient management for screening, diagnosis, and treatment.

HIV-1 Envelope Overcomes NLRP3-Mediated Inhibition of F-Actin Polymerization for Viral Entry

Purinergic receptors and nucleotide-binding domain leucine-rich repeat containing (NLR) proteins have been shown to control viral infection. Here, we show that the NLR family member NLRP3 and the purinergic receptor P2Y2 constitutively interact and regulate susceptibility to HIV-1 infection. We found that NLRP3 acts as an inhibitory factor of viral entry that represses F-actin remodeling. The binding of the HIV-1 envelope to its host cell receptors (CD4, CXCR4, and/or CCR5) overcomes this restriction by stimulating P2Y2. Once activated, P2Y2 enhances its interaction with NLRP3 and stimulates the recruitment of the E3 ubiquitin ligase CBL to NLRP3, ultimately leading to NLRP3 degradation. NLRP3 degradation is permissive for PYK2 phosphorylation (PYK2Y402^∗) and subsequent F-actin polymerization, which is required for the entry of HIV-1 into host cells. Taken together, our results uncover a mechanism by which HIV-1 overcomes NLRP3 restriction that appears essential for the accomplishment of the early steps of HIV-1 entry.

New Insights into the Mechanisms of Pyroptosis and Implications for Diabetic Kidney Disease

Pyroptosis is one special type of lytic programmed cell death, featured in cell swelling, rupture, secretion of cell contents and remarkable proinflammation effect. In the process of pyroptosis, danger signalling and cellular events are detected by inflammasome, activating caspases and cleaving Gasdermin D (GSDMD), along with the secretion of IL-18 and IL-1β. Pyroptosis can be divided into canonical pathway and non-canonical pathway, and NLRP3 inflammasome is the most important initiator. Diabetic kidney disease (DKD) is one of the most serious microvascular complications in diabetes. Current evidence reported the stimulatory role of hyperglycaemia-induced cellular stress in renal cell pyroptosis, and different signalling pathways have been shown to regulate pyroptosis initiation. Additionally, the inflammation and cellular injury caused by pyroptosis are tightly implicated in DKD progression, aggravating renal fibrosis, glomerular sclerosis and tubular injury. Some registered hypoglycaemia agents exert suppressive activity in pyroptosis regulation pathway. Latest studies also reported some potential approaches to target the pyroptosis pathway, which effectively inhibits renal cell pyroptosis and alleviates DKD in in vivo or in vitro models. Therefore, comprehensively compiling the information associated with pyroptosis regulation in DKD is the main aim of this review, and we try to provide new insights for researchers to dig out more potential therapies of DKD.

Inflammasome Fuels Dengue Severity

Dengue is an acute febrile disease triggered by dengue virus. Dengue is the widespread and rapidly transmitted mosquito-borne viral disease of humans. Diverse symptoms and diseases due to Dengue virus (DENV) infection ranges from dengue fever, dengue hemorrhagic fever (life-threatening) and dengue shock syndrome characterized by shock, endothelial dysfunction and vascular leakage. Several studies have linked the severity of dengue with the induction of inflammasome. DENV activates the NLRP3-specific inflammasome in DENV infected human patients, mice; specifically, mouse bone marrow derived macrophages (BMDMs), dendritic cells, endothelial cells, human peripheral blood mononuclear cells (PBMCs), keratinocytes, monocyte-differentiated macrophages (THP-1), and platelets. Dengue virus mediated inflammasome initiates the maturation of IL-1β and IL-18, which are critical for dengue pathology and inflammatory response. Several studies have reported the molecular mechanism through which (host and viral factors) dengue induces inflammasome, unravels the possible mechanisms of DENV pathogenesis and sets up the stage for the advancement of DENV therapeutics. In this perspective article, we discuss the potential implications and our understanding of inflammasome mechanisms of dengue virus and highlight research areas that have potential to inhibit the pathogenesis of viral diseases, specifically for dengue.

Inflammasome activation in podocytes: a new mechanism of glomerular diseases

INTRODUCTION

Inflammasome is a multi-protein complex which is an important constituent of innate immunity. It mainly consists of three parts, apoptosis-associated speck-like protein containing caspase recruitment domain (ASC), caspase protease, and a NOD-like receptor (NLR) family protein (such as NLRP1) or an HIN200 family protein (such as AIM2). Inflammasome is widely studied in many autoimmune diseases and chronic inflammatory reactions, such as familial periodic autoinflammatory response, type 2 diabetes, Alzheimer's disease, and atherosclerosis. Activation of inflammasome in the kidney has been widely reported in glomerular and tubular-interstitial diseases. Podocytes play a critical role in maintaining the normal structure and function of glomerular filtration barrier. Recently, it has been demonstrated that podocytes, as a group of renal residential cells, can express all necessary components of NLRP3 inflammasome, which is activated and contribute to inflammatory response in the local kidney.

METHODS

Literature review was conducted to further summarize current evidence of podocyte NLRP3 inflammasome activation and related molecular mechanisms under different disease conditions.

RESULTS

Podocytes are a key component of the glomerular filtration barrier, and the loss of podocyte regeneration is a major limiting factor in the recovery of proteinuria. Through a more comprehensive study of inflammasome in podocytes, it will provide new targets and possibilities for the treatment of kidney diseases.

NLRP3 Inflammasome-A Key Player in Antiviral Responses

The NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome is an oligomeric complex comprised of the NOD-like receptor NLRP3, the adaptor ASC, and caspase-1. This complex is crucial to the host's defense against microbes as it promotes IL-1β and IL-18 secretion and induces pyroptosis. NLRP3 recognizes variety of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) generated during viral replication that triggers the NLRP3 inflammasome-dependent antiviral immune responses and facilitates viral eradication. Meanwhile, several viruses have evolved elaborate strategies to evade the immune system by targeting the NLRP3 inflammasome. In this review, we will focus on the crosstalk between the NLRP3 inflammasome and viruses, provide an overview of viral infection-induced NLRP3 inflammasome activation, and the immune escape strategies of viruses through their modulation of the NLRP3 inflammasome activity.

The role of inflammasomes in kidney disease

Inflammasomes are multiprotein innate immune complexes that regulate caspase-dependent inflammation and cell death. Pattern recognition receptors, such as nucleotide-binding oligomerization domain (NOD)-like receptors and absent in melanoma 2 (AIM2)-like receptors, sense danger signals or cellular events to activate canonical inflammasomes, resulting in caspase 1 activation, pyroptosis and the secretion of IL-1β and IL-18. Non-canonical inflammasomes can be activated by intracellular lipopolysaccharides, toxins and some cell signalling pathways. These inflammasomes regulate the activation of alternative caspases (caspase 4, caspase 5, caspase 11 and caspase 8) that lead to pyroptosis, apoptosis and the regulation of other cellular pathways. Many inflammasome-related genes and proteins have been implicated in animal models of kidney disease. In particular, the NLRP3 (NOD-, LRR- and pyrin domain-containing 3) inflammasome has been shown to contribute to a wide range of acute and chronic microbial and non-microbial kidney diseases via canonical and non-canonical mechanisms that regulate inflammation, pyroptosis, apoptosis and fibrosis. In patients with chronic kidney disease, immunomodulation therapies targeting IL-1β such as canakinumab have been shown to prevent cardiovascular events. Moreover, findings in experimental models of kidney disease suggest that small-molecule inhibitors targeting NLRP3 and other inflammasome components are promising therapeutic agents.

Alterations in plasma membrane ion channel structures stimulate NLRP3 inflammasome activation in APOL1 risk milieu

We evaluated alterations in the structural configurations of channels and activation of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome formation in apolipoprotein L1 (APOL1) risk and nonrisk milieus. APOL1G1- and APOL1G2-expressing podocytes (PD) displayed enhanced K⁺ efflux, induction of pyroptosis, and escalated transcription of interleukin (IL)-1β and IL-18. APOL1G1- and APOL1G2-expressing PD promoted the transcription as well as translation of proteins involved in the formation of inflammasomes. Since glyburide (a specific inhibitor of K⁺ efflux channels) inhibited the transcription of NLRP3, IL-1β, and IL-18, the role of K⁺ efflux in the activation of inflammasomes in APOL1 risk milieu was implicated. To evaluate the role of structural alterations in K⁺ channels in plasma membranes, bioinformatics studies, including molecular dynamic simulation, were carried out. Superimposition of bioinformatics reconstructions of APOL1G0, G1, and G2 showed several aligned regions. The analysis of pore-lining residues revealed that Ser342 and Tyr389 are involved in APOL1G0 pore formation and the altered conformations resulting from the Ser342Gly and Ile384Met mutation in the case of APOLG1 and deletion of the Tyr389 residue in the case of APOL1G2 are expected to alter pore characteristics, including K⁺ ion selectivity. Analysis of multiple membrane (lipid bilayer) models of interaction with the peripheral protein, integral membrane protein, and multimer protein revealed that for an APOL1 multimer model, APOL1G0 is not energetically favorable while the APOL1G1 and APOL1G2 moieties favor the insertion of multiple ion channels into the lipid bilayer. We conclude that altered pore configurations carry the potential to facilitate K⁺ ion transport in APOL1 risk milieu.

Caspase-1 Activation Is Related With HIV-Associated Atherosclerosis in an HIV Transgenic Mouse Model and HIV Patient Cohort

OBJECTIVE

Atherosclerotic cardiovascular disease (ASCVD) is an increasing cause of morbidity and mortality in people with HIV since the introduction of combination antiretroviral therapy. Despite recent advances in our understanding of HIV ASCVD, controversy still exists on whether this increased risk of ASCVD is due to chronic HIV infection or other risk factors. Mounting biomarker studies indicate a role of monocyte/macrophage activation in HIV ASCVD; however, little is known about the mechanisms through which HIV infection mediates monocyte/macrophage activation in such a way as to engender accelerated atherogenesis. Here, we experimentally investigated whether HIV expression is sufficient to accelerate atherosclerosis and evaluated the role of caspase-1 activation in monocytes/macrophages in HIV ASCVD. Approach and Results: We crossed a well-characterized HIV mouse model, Tg26 mice, which transgenically expresses HIV-1, with ApoE-/- mice to promote atherogenic conditions (Tg26+/-/ApoE-/-). Tg26+/-/ApoE-/- have accelerated atherosclerosis with increased caspase-1 pathway activation in inflammatory monocytes and atherosclerotic vasculature compared with ApoE-/-. Using a well-characterized cohort of people with HIV and tissue-banked aortic plaques, we documented that serum IL (interleukin)-18 was higher in people with HIV compared with non-HIV-infected controls, and in patients with plaques, IL-18 levels correlated with monocyte/macrophage activation markers and noncalcified inflammatory plaques. In autopsy-derived aortic plaques, caspase-1+ cells and CD (clusters of differentiation) 163+ macrophages correlated.

CONCLUSIONS

These data demonstrate that expression of HIV is sufficient to accelerate atherogenesis. Further, it highlights the importance of caspase-1 and monocyte/macrophage activation in HIV atherogenesis and the potential of Tg26+/-/ApoE-/- as a tool for mechanistic studies of HIV ASCVD.

Elevated indoleamine-2,3-dioxygenase enzyme activity in a novel mouse model of HIV-associated atherosclerosis

OBJECTIVE

HIV atherosclerosis and cardiovascular disease (CVD) represent a significant human health burden in the era of combination antiretroviral therapy (cART). The pathogenesis of HIV atherosclerosis is still poorly understood, due, in part, to the lack of a suitable small animal model. Indoleamine-2,3-dioxygenase (IDO) enzyme activity is the first and rate-limiting step in tryptophan catabolism and is measured by the kynurenine to tryptophan ratio (KTR). The serum KTR is a biomarker of inflammation and has recently been implicated as an important risk factor for CVD in patients living with HIV (PLWH) who are virologically suppressed under cART. However, IDO activity in HIV-associated CVD has not been studied in mouse model before.

DESIGN

A novel mouse model of HIV atherosclerosis (Tg26/ApoE) was generated and examined for IDO activity and atherogenesis throughout 8 weeks on a high-fat diet. Tg26/ApoE mice were compared with Tg26 and ApoE single transgenic mice, before and during a high-fat diet.

METHOD

Serum kynurenine, tryptophan and percentage of aortic plaque formation were measured. Additionally, levels of relevant cytokines were investigated in Tg26/ApoE and ApoE.

RESULTS

Tg26/ApoE developed an accelerated atherosclerosis with increasing levels of KTR that were associated with plaque progression. This accelerated plaque was potentially driven by elevated levels of circulating IL-6.

CONCLUSION

These results indicate that Tg26/ApoE serve as a new mouse model for HIV-induced atherogenesis, and aid in understanding the role of tryptophan catabolism in the pathogenesis of HIV atherosclerosis/CVD.

APOL1 and kidney cell function

The apolipoprotein L1 (APOL1) gene is unique to humans and gorillas and appeared ~33 million years ago. Since the majority of the mammals do not carry APOL1, it seems to be dispensable for kidney function. APOL1 renal risk variants (RRVs; G1 and G2) are associated with the development as well as progression of chronic kidney diseases (CKDs) at higher rates in populations with African ancestry. Cellular expression of two APOL1 RRVs has been demonstrated to induce cytotoxicity, including necrosis, apoptosis, and pyroptosis, in several cell types including podocytes; mechanistically, these toxicities were attributed to lysosomal swelling, K⁺ depletion, mitochondrial dysfunction, autophagy blockade, protein kinase receptor activation, ubiquitin D degradation, and endoplasmic reticulum stress; notably, these effects were found to be dose dependent and occurred only in overtly APOL1 RRV-expressing cells. However, cellular protein expressions as well as circulating blood levels of APOL1 RRVs were not elevated in patients suffering from APOL1 RRV-associated CKDs. Therefore, the question arises as to whether it is gain or loss of function on the part of APOL1 RRVs contributing to kidney cell injury. The question seems to be more pertinent after the recognition of the role of APOL1 nonrisk (G0) in the transition of parietal epithelial cells and preservation of the podocyte molecular phenotype through modulation of the APOL1-miR-193a axis. With this background, the present review analyzed the available literature in terms of the known function of APOL1 nonrisk and how the loss of these functions could have contributed to two APOL1 RRV-associated CKDs.

Evaluation of Canonical Inflammasome Activation in Human Monocytes by Imaging Flow Cytometry

Canonical inflammasome activation is a tightly regulated process that has been implicated in a broad spectrum of inflammatory disorders. Inflammasome formation requires assembly of a cytosolic sensor protein with the adapter, ASC (apoptosis-associated speck-like protein containing a caspase activating and recruitment domain). Once formed, this multimeric protein structure allows for the activation of caspase-1, responsible for IL-1ß/IL-18 release. During this process, cytoplasmic dispersed ASC molecules cluster in one condensed micrometric-sized complex named ASC “speck,” which is traditionally assessed by fluorescence microscopy and widely accepted as a readout for canonical inflammasome activation. However, equally reliable but less time-consuming quantitative methods have emerged as a significant need in order to improve clinical assessment of inflammasome-related conditions. Multispectral imaging flow cytometry (MIFC) combines the qualitative power of fluorescence microscopy with high throughput capabilities and multiplexing potential of flow cytometry into one single system. Here we explored the optimal imaging-based tools to measure ASC speck formation via imaging flow cytometry by using peripheral blood mononuclear cells (PBMCs) stimulated with the NLRP3 agonist Nigericin, as a positive control. We demonstrate that this technique is also able to detect the distribution of active caspase-1 within the ASC aggregates by incubating cells with FAM-FLICA^TM, a fluorochrome inhibitor of caspase-1. By applying these tools in PBMCs from patients with distinct inflammatory disorders we demonstrate that MIFC is able to assess canonical inflammasome activation in a quantitative and statistically robust manner in clinically relevant samples. Therefore, we propose that accurate assessment of specks by MIFC could help guide preventive or therapeutic strategies in an array of human inflammatory diseases in which inflammasomes play an important role.

Role of the inflammasomes in HIV-associated neuroinflammation and neurocognitive disorders

HIV associated neurocognitive disorders (HAND) is a unique form of neurological impairment that stems from HIV. This disease and its characteristics can be accredited to incorporation of DNA and mRNA of HIV-1 into the CNS. A proper understanding of the intricacies of HAND and the underlying mechanisms associated with corresponding immune reactions are vital for the potential development of a reliable treatment for HAND. A common phenomenon observed in CNS cells, specifically microglia, that are infected with HAND is inflammation, which is a consequence of the activation of innate immune response due to a variety of stimuli, in this case, being the HIV infection. The CNS based inflammation is mediated by the production of cytokines, chemokines, reactive oxygen species, and secondary messengers, which occurs at CNS glia, endothelial cells and peripherally derived immune cells. Inflammasomes play a significant role with regard to neuroinflammation due to their ability to dictate the activation of various inflammatory responses. Certain stimuli can result in the activation of caspase-1; hence, leading to the processing of interleukin-1β and interleukin-18 pro-inflammatory cytokines. The processed IL-1β and IL-18 activate signaling pathways that begin the process of neuroinflammation. Due to the fact that the NLRP3 inflammasome is the most abundant in the CNS, it is the most extensively investigated inflammasome with regard to the nervous system. Due to the importance of neuroinflammation in the evolution of HAND and proliferation of neuroinflammation due to HAND, it can be concluded that there exists a relationship between HAND and inflammasomes. The aim of our review is to consolidate current knowledge of important mechanisms in HAND, specifically related to its relationship with neuroinflammation and inflammasomes to shed light on a possible improved treatment for HAND.

P2X Antagonists Inhibit HIV-1 Productive Infection and Inflammatory Cytokines Interleukin-10 (IL-10) and IL-1β in a Human Tonsil Explant Model

HIV-1 causes a persistent infection of the immune system that is associated with chronic comorbidities. The mechanisms that underlie this inflammation are poorly understood. Emerging literature has implicated proinflammatory purinergic receptors and downstream signaling mediators in HIV-1 infection. This study probed whether inhibitors of purinergic receptors would reduce HIV-1 infection and HIV-1-stimulated inflammation. An ex vivo human tonsil histoculture infection model was developed to support HIV-1 productive infection and stimulated the inflammatory cytokine interleukin-1 beta (IL-1β) and the immunosuppressive cytokine interleukin-10 (IL-10). This study tests whether inhibitors of purinergic receptors would reduce HIV-1 infection and HIV-1-stimulated inflammation. The purinergic P2X1 receptor antagonist NF449, the purinergic P2X7 receptor antagonist A438079, and azidothymidine (AZT) were tested in HIV-1-infected human tonsil explants to compare levels of inhibition of HIV-1 infection and HIV-stimulated inflammatory cytokine production. All drugs limited HIV-1 productive infection, but P2X-selective antagonists (NF449 and A438079) significantly lowered HIV-stimulated IL-10 and IL-1β. We further observed that P2X1- and P2X7-selective antagonists can act differentially as inhibitors of both HIV-1 infection and HIV-1-stimulated inflammation. Our findings highlight the differential effects of HIV-1 on inflammation in peripheral blood compared to those in lymphoid tissue. For the first time, we demonstrate that P2X-selective antagonists act differentially as inhibitors of both HIV-1 infection and HIV-1-stimulated inflammation. Drugs that block these pathways can have independent inhibitory activities against HIV-1 infection and HIV-induced inflammation.IMPORTANCE Patients who are chronically infected with HIV-1 experience sequelae related to chronic inflammation. The mechanisms of this inflammation have not been elucidated. Here, we describe a class of drugs that target the P2X proinflammatory signaling receptors in a human tonsil explant model. This model highlights differences in HIV-1 stimulation of lymphoid tissue inflammation and peripheral blood. These drugs serve to block both HIV-1 infection and production of IL-10 and IL-1β in lymphoid tissue, suggesting a novel approach to HIV-1 therapeutics in which both HIV-1 replication and inflammatory signaling are simultaneously targeted.

NLRP3 deficiency exacerbates enterovirus infection in mice

The role for the NOD-like receptor (NLR) P3 inflammasome in enterovirus infection remains controversial. Available data suggest that the NLRP3 inflammasome is protective against enterovirus A71 but detrimental to the host during coxsackievirus B3 (CVB3) infection. CVB3 is a common etiologic agent associated with myocarditis and pancreatitis. Previous findings on the role of NLRP3 in CVB3 were based primarily on indirect evidence. Here, we utilized NLRP3 knockout mice as well as immune and cardiac cells to investigate the direct interplay between CVB3 infection and NLRP3 activation. We demonstrated that NLRP3 knockout mice exhibited more severe disease phenotype after CVB3 infection (significantly higher virus titers), increased myocardial, and pancreatic damage, as well as markedly impaired cardiac function compared to nontransgenic control mice. We further showed that NLRP3 activity was enhanced during early stage of CVB3 infection, as evidenced by increased gene expression and/or secretion of IL-1β and caspase-1. Finally, we demonstrated that CVB3 inactivates the NLRP3 inflammasome by degrading NLRP3 and its upstream serine/threonine-protein kinase receptor-interacting protein 1/3 via the proteolytic activity of virus-encoded proteinases. Taken together, our results reveal the functional significance of NLRP3 in host antiviral immunity against CVB3 infection and the mechanisms by which CVB3 has evolved to counteract the host defense response.-Wang, C., Fung, G., Deng, H., Jagdeo, J., Mohamud, Y., Xue, Y. C., Jan, E., Hirota, J. A., Luo, H. NLRP3 deficiency exacerbates enterovirus infection in mice.

Cytosolic Recognition of Microbes and Pathogens: Inflammasomes in Action

Infection is a dynamic biological process underpinned by a complex interplay between the pathogen and the host. Microbes from all domains of life, including bacteria, viruses, fungi, and protozoan parasites, have the capacity to cause infection. Infection is sensed by the host, which often leads to activation of the inflammasome, a cytosolic macromolecular signaling platform that mediates the release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 and cleavage of the pore-forming protein gasdermin D, leading to pyroptosis. Host-mediated sensing of the infection occurs when pathogens inject or carry pathogen-associated molecular patterns (PAMPs) into the cytoplasm or induce damage that causes cytosolic liberation of danger-associated molecular patterns (DAMPs) in the host cell. Recognition of PAMPs and DAMPs by inflammasome sensors, including NLRP1, NLRP3, NLRC4, NAIP, AIM2, and Pyrin, initiates a cascade of events that culminate in inflammation and cell death. However, pathogens can deploy virulence factors capable of minimizing or evading host detection. This review presents a comprehensive overview of the mechanisms of microbe-induced activation of the inflammasome and the functional consequences of inflammasome activation in infectious diseases. We also explore the microbial strategies used in the evasion of inflammasome sensing at the host-microbe interaction interface.

A Single Locus Controls Interferon Gamma-Independent Antiretroviral Neutralizing Antibody Responses

An essential step in the development of effective antiviral humoral responses is cytokine-triggered class switch recombination resulting in the production of antibodies of a specific isotype. Most viral and parasitic infections in mice induce predominantly IgG2a-specific antibody responses that are stimulated by interferon gamma (IFN-γ). However, in some mice deficient in IFN-γ, class switching to IgG2a antibodies is relatively unaffected, indicating that another signal(s) can be generated upon viral or parasitic infections that trigger this response. Here, we found that a single recessive locus, provisionally called IFN-γ-independent IgG2a (Igii), confers the ability to produce IFN-γ-independent production of IgG2a antibodies upon retroviral infection. The Igii locus was mapped to chromosome 9 and was found to function in the radiation-resistant compartment. Thus, our data implicate nonhematopoietic cells in activation of antiviral antibody responses in the absence of IFN-γ.IMPORTANCE Understanding the signals that stimulate antibody production and class switch recombination to specific antibody isotypes is crucial for the development of novel vaccines and adjuvants. While an interferon gamma-mediated switch to the IgG2a isotype upon viral infection in mice has been well established, this investigation reveals a noncanonical, interferon gamma-independent pathway for antiretroviral antibody production and IgG2a class switch recombination that is controlled by a single recessive locus. Furthermore, this study indicates that the radiation-resistant compartment can direct antiviral antibody responses, suggesting that detection of infection by nonhematopoietic cells is involved is stimulating adaptive immunity.

Cardiomyocyte Inflammasome Signaling in Cardiomyopathies and Atrial Fibrillation: Mechanisms and Potential Therapeutic Implications

Inflammasomes are high molecular weight protein complexes in the cytosol of immune and other cells that play a critical role in the innate immune system in response to cellular stress. NLRP3 inflammasome, the best-understood inflammasome, is known to mediate the maturation (activation) of caspase-1 from pro-caspase-1, causing the maturation and release of cytokines (e.g., interleukin-1β) and potentially leading to a form of inflammatory programmed cell death called pyroptosis. Previous work has shown that the NLRP3 components are expressed in cardiomyocytes and cardiac fibroblasts and recent studies have identified the NLRP3 inflammasome as a key nodal point in the pathogenesis of cardiomyopathies and atrial fibrillation, which may create an opportunity for the development of new therapeutic agents. Here we review the recent evidence for a role of NLRP3 inflammasome in the cardiomyocytes and discuss its potential role in the evolution of cardiac remodeling and arrhythmias and new opportunities created by these very recent developments.

Lower High-Density Lipoproteins Levels During Human Immunodeficiency Virus Type 1 Infection Are Associated With Increased Inflammatory Markers and Disease Progression

Introduction

High-density lipoproteins (HDL) are responsible for the efflux and transport of cholesterol from peripheral tissues to the liver. In addition, HDL can modulate various immunological mechanisms, including the inflammatory response. Inflammasomes are multiprotein complexes that have been reported to be activated during human immunodeficiency virus type 1 (HIV-1) infection, thus contributing to immune hyperactivation, which is the main pathogenic mechanism of HIV-1 progression. However, the relationship between HDL and inflammasomes in the context of HIV-1 infection is unclear. Therefore, this research aims to explore the association between HDL and the components of the inflammatory response during HIV-1 infection.

Methodology

A cross-sectional study, including 36 HIV-1-infected individuals without antiretroviral treatment and 36 healthy controls matched by sex and age, was conducted. Viral load, CD4+ T-cell counts, serum HDL, and C-reactive protein (CRP) were quantified. Serum cytokine levels, including IL-1β, IL-6, and IL-18, were assessed by ELISA. The inflammasome-related genes in peripheral blood mononuclear cells were determined by quantitative real-time PCR.

Results

HIV-1-infected individuals showed a significant decrease in HDL levels, particularly those subjects with higher viral load and lower CD4+ T-cell counts. Moreover, upregulation of inflammasome-related genes (NLRP3, AIM2, ASC, IL-1β, and IL-18) was observed, notably in those HIV-1-infected individuals with higher viral loads (above 5,000 copies/mL). Serum levels of IL-6 and CRP were also elevated in HIV-1-infected individuals. Significant negative correlations between HDL and the mRNA of NLRP3, AIM2, ASC, IL-1β, and IL-18, as well as viral load and CRP were observed in HIV-1-infected individuals. Likewise, a significant positive correlation between HDL and CD4+ T-cell counts was found.

Conclusion

In summary, our results indicate that HDL might modulate the expression of several key components of the inflammasomes during HIV-1 infection, suggesting a novel role of HDL in modifying the inflammatory state and consequently, the progression of HIV-1 infection.

Molecular Mechanisms of Injury in HIV-Associated Nephropathy

HIV-associated nephropathy (HIVAN) is an important cause of secondary focal glomerulosclerosis that occurs primarily in persons of African ancestry with advanced HIV disease. Although HIVAN is characterized by severe proteinuria and rapid progression to end stage renal disease without treatment, the phenotype is markedly attenuated by treatment with antiretroviral medications. HIV infection of glomerular and tubular epithelial cells and subsequent viral gene expression is a key contributor to HIVAN pathogenesis and the kidney can serve as reservoir for HIV strains that differ those in blood. HIV gene expression in renal epithelial cells leads to dysregulation of cellular pathways including cell cycle, inflammation, cell death, and cytoskeletal homeostasis. Polymorphisms in the APOL1 gene explain the marked predilection of HIVAN to occur in persons of African descent and HIVAN. Since HIVAN has the strongest association with APOL1 genotype of any of the APOL1-associated nephropathies, studies to determine the mechanisms by which HIV and APOL1 risk variants together promote kidney injury hold great promise to improve our understanding of the pathogenesis of APOL1-mediated kidney diseases.

APOL1: The Balance Imposed by Infection, Selection, and Kidney Disease

Chronic kidney disease (CKD) affects millions of people and constitutes a major health and financial burden worldwide. People of African descent are at an increased risk of developing kidney disease, which is mostly explained by two variants in the Apolipoprotein L1 (APOL1) gene that are found only in people of west African origin. It is hypothesized that these variants were genetically selected due to the protection they afford against African sleeping sickness, caused by the parasite Trypanosoma brucei. Targeting mutant APOL1 could have substantial therapeutic potential for treating kidney disease. In this review, we will describe the intriguing interplay between microbiology, genetics, and kidney disease as revealed in APOL1-associated kidney disease, discuss APOL1-induced cytotoxicity and its therapeutic implications.

Tetrahydroxy Stilbene Glucoside Alleviates High Glucose-Induced MPC5 Podocytes Injury Through Suppression of NLRP3 Inflammasome

BACKGROUND

Tetrahydroxy stilbene glucoside (TSG) is an active ingredient of Heshouwu and is an antioxidant. The underlying mechanisms of the renoprotective effect of TSG in diabetic nephropathy have not been previously reported. In this study, we investigated the mechanisms of TSG in preventing podocytes injury in high glucose (HG) condition.

METHODS

Cultured mouse podocytes (MPC5) were incubated in HG (30mmol/L) plus various concentration of TSG (0.1, 1 and 10μM) for 48 hours. Reactive oxygen species (ROS) production, malondialdehyde (MDA) levels, terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end-labeling (TUNEL) fluorescence intensity, caspase-3 activity and the mRNA expression of nephrin in cultured podocytes were determined. The protein expression of Nod-like receptor protein 3 (NLRP3) inflammsome, interleukin-1β (IL-1β) and nephrin was detected by Western blot.

RESULTS

When the podocytes were incubated with various concentrations of TSG under HG conditions for 48 hours, TSG decreased ROS production, MDA levels, TUNEL fluorescence intensity and caspase-3 activity, but increased cell viability and the expression of nephrin in HG-induced podocytes in a dose-dependent manner. Subsequently, the podocytes treated with TSG at 10 μΜ decreased the expression of NLRP3 inflammasome and IL-1β compared with that of control. Furthermore, the podocytes transfected with NLRP3- small interfering RNA (siRNA) exhibited a significant decrease in the expression of caspase-1 and IL-1β, but exhibited a significant increase in the expression of nephrin. Eventually, TSG significantly increased the expression of nephrin in IL-1β-treated podocytes.

CONCLUSIONS

TSG attenuates high glucose-induced cell apoptosis in vitro partly through the suppression of NLRP3 inflammasome signaling.

Live or Let Die: Is There any Cell Death in Podocytes?

Ultimately, the common final pathway of any glomerular disease is podocyte effacement, podocyte loss, and, eventually, glomerular scarring. There has been a long-standing debate on the underlying mechanisms for podocyte depletion, ranging from necrosis and apoptosis to detachment of viable cells from the glomerular basement membrane. However, this debate still continues because additional pathways of programmed cell death have been reported in recent years. Interestingly, viable podocytes can be isolated out of the urine of proteinuric patients easily, emphasizing the importance of podocyte detachment in glomerular diseases. In contrast, detection of apoptosis and other pathways of programmed cell death in podocytes is technically challenging. In fact, we still are lacking direct evidence showing, for example, the presence of apoptotic bodies in podocytes, leaving the question unanswered as to whether podocytes undergo mechanisms of programmed cell death. However, understanding the mechanisms leading to podocyte depletion is of particular interest because future therapeutic strategies might interfere with these to prevent glomerular scarring. In this review, we summarize our current knowledge on podocyte cell death, the different molecular pathways and experimental approaches to study these, and, finally, focus on the mechanisms that prevent the onset of programmed cell death.

HIV-Associated Nephropathy in Africa: Pathology, Clinical Presentation and Strategy for Prevention

The human immunodeficiency virus (HIV) infection can lead to progressive decline in renal function known as HIV-associated nephropathy (HIVAN). Importantly, individuals of African ancestry are more at risk of developing HIVAN than their European descent counterparts. An in-depth search on Google Scholar, Medline and PubMed was conducted using the terms "HIVAN" and "pathology and clinical presentation", in addition to "prevalence and risk factors for HIVAN", with special emphasis on African countries for any articles published between 1990 and 2017. HIVAN is characterized by progressive acute renal failure, proteinuria and enlarged kidneys. A renal biopsy is necessary to establish definitive diagnosis. Risk factors are male gender, low CD4 counts, high viral load and long use of combined antiretroviral medication (cART). There is a wide geographical variation in the prevalence of HIVAN as it ranges from 4.7% to 38% worldwide and little published literature is available about its prevalence in African nations. Microalbuminuria is a common finding in African populations and is significantly associated with severity of HIV disease progression and CD4 count less than 350 cells/µL. Other clinical presentations in African populations include acute kidney injury (AKI), nephrotic syndrome and chronic kidney disease. The main HIV-associated renal pathological lesions were focal segmental glomerulosclerosis, mainly the collapsing form, acute interstitial nephritis (AIN), and immune complex-mediated glomerulonephritis (ICGN). HIV infection-induced transcriptional program in renal tubular epithelial cells as well as genetic factors is incriminated in the pathogenesis of HIVAN. This narrative review discusses the prevalence, presentation, pathogenesis and the management of HIVAN in Africa. In low resource setting countries in Africa, dealing with HIV complications like HIVAN may add more of a burden on the health system (particularly renal units) than HIV medication itself. Therefore, the obvious recommendation is early use of cART in order to decrease risk factors that lead to HIVAN.

Activation and Role of NACHT, LRR, and PYD Domains-Containing Protein 3 Inflammasome in RNA Viral Infection

NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation and effects during ribonucleic acid (RNA) viral infection are the focus of a wide range of research currently. Both the pathogen-associated molecule pattern derived from virions and intracellular stress molecules involved in the process of viral infection lead to activation of the NLRP3 inflammasome, which in turn triggers inflammatory responses for antiviral defense and tissue healing. However, aberrant activation of the NLRP3 inflammasome can instead support viral pathogenesis and promote disease progression. Here, we summarize and expound upon the recent literature describing the molecular mechanisms underlying the activation and effects of the NLRP3 inflammasome in RNA viral infection to highlight how it provides protection against RNA viral infection.

HIV-1-Associated Atherosclerosis: Unraveling the Missing Link

Cardiovascular disease, including atherosclerosis and atherosclerosis-associated complications, is an increasing cause of morbidity and mortality in human immunodeficiency virus (HIV) patients in the post-antiretroviral therapy era. HIV alone accelerates atherosclerosis. Antiretroviral therapy; HIV-associated comorbidities, such as dyslipidemia, drug abuse, and opportunistic infections; and lifestyle are risk factors for HIV-associated atherosclerosis. However, our current understanding of HIV-associated atherogenesis is very limited and has largely been obtained from clinical observation. There is a pressing need to experimentally unravel the missing link between HIV and atherosclerosis. Understanding these mechanisms will help to better develop and design novel therapeutic interventions for the treatment of HIV-associated cardiovascular disease. HIV mainly infects T cells and macrophages resulting in the induction of oxidative and endoplasmic reticulum stress, the formation of the inflammasome, and the dysregulation of autophagy. These mechanisms may contribute to HIV-associated atherogenesis. In this review, we will summarize our current understanding and propose potential mechanisms of HIV-associated atherosclerosis.