EC144, a synthetic inhibitor of heat shock protein 90, blocks innate and adaptive immune responses in models of inflammation and autoimmunity

Potential role of immunotherapy and targeted therapy in the treatment of cancer: A contemporary nursing practice

Immunotherapy and targeted therapy have emerged as promising therapeutic options for cancer patients. Immunotherapies induce a host immune response that mediates long-lived tumor destruction, while targeted therapies suppress molecular mechanisms that are important for tumor maintenance and growth. In addition, cytotoxic agents and targeted therapies regulate immune responses, which increases the chances that these therapeutic approaches may be efficiently combined with immunotherapy to ameliorate clinical outcomes. Various studies have suggested that combinations of therapies that target different stages of anti-tumor immunity may be synergistic, which can lead to potent and more prolonged responses that can achieve long-lasting tumor destruction. Nurses associated with cancer patients should have a better understanding of the immunotherapies and targeted therapies, such as their efficacy profiles, mechanisms of action, as well as management and prophylaxis of adverse events. Indeed, this knowledge will be important in establishing care for cancer patients receiving immunotherapies and targeted therapies for cancer treatment. Moreover, nurses need a better understanding regarding targeted therapies and immunotherapies to ameliorate outcomes in patients receiving these therapies, as well as management and early detection of possible adverse effects, especially adverse events associated with checkpoint inhibitors and various other therapies that control T-cell activation causing autoimmune toxicity. Nurses practice in numerous settings, such as hospitals, home healthcare agencies, radiation therapy facilities, ambulatory care clinics, and community agencies. Therefore, as compared to other members of the healthcare team, nurses often have better opportunities to develop the essential rapport in providing effective nurse-led patient education, which is important for effective therapeutic outcomes and continuance of therapy. In this article, we have particularly focused on providing a detailed overview on targeted therapies and immunotherapies used in cancer treatment, management of their associated adverse events, and the impact as well as strategies of nurse-led patient education.

Heat shock protein 90 inhibition attenuates inflammation in models of atopic dermatitis: a novel mechanism of action

Background

Heat shock protein 90 (HSP90) is an important chaperone supporting the function of many proinflammatory client proteins. Recent studies indicate HSP90 inhibition may be a novel mechanism of action for inflammatory skin diseases; however, this has not been explored in atopic dermatitis (AD).

Objectives

Our study aimed to investigate HSP90 as a novel target to treat AD.

Methods

Experimental models of AD were used including primary human keratinocytes stimulated with cytokines (TNF/IFNγ or TNF/IL-4) and a mouse model established by MC903 applications.

Results

In primary human keratinocytes using RT-qPCR, the HSP90 inhibitor RGRN-305 strongly suppressed the gene expression of Th1- (TNF, IL1B, IL6) and Th2-associated (CCL17, CCL22, TSLP) cytokines and chemokines related to AD. We next demonstrated that topical and oral RGRN-305 robustly suppressed MC903-induced AD-like inflammation in mice by reducing clinical signs of dermatitis (oedema and erythema) and immune cell infiltration into the skin (T cells, neutrophils, mast cells). Interestingly, topical RGRN-305 exhibited similar or slightly inferior efficacy but less weight loss compared with topical dexamethasone. Furthermore, RNA sequencing of skin biopsies revealed that RGRN-305 attenuated MC903-induced transcriptome alterations, suppressing genes implicated in inflammation including AD-associated cytokines (Il1b, Il4, Il6, Il13), which was confirmed by RT-qPCR. Lastly, we discovered using Western blot that RGRN-305 disrupted JAK-STAT signaling by suppressing the activity of STAT3 and STAT6 in primary human keratinocytes, which was consistent with enrichment analyses from the mouse model.

Conclusion

HSP90 inhibition by RGRN-305 robustly suppressed inflammation in experimental models mimicking AD, proving that HSP90 inhibition may be a novel mechanism of action in treating AD.

Efficacy and Safety of the Heat Shock Protein 90 Inhibitor RGRN-305 in Hidradenitis Suppurativa: A Parallel-Design Double-Blind Trial

Importance

Hidradenitis suppurativa is a painful immune-mediated disorder with limited treatment options; hence, a need exists for new treatments.

Objective

To evaluate the feasibility of heat shock protein 90 inhibition by RGRN-305 as a novel mechanism of action in treating moderate to severe hidradenitis suppurativa.

Design, Setting, and Participants

This was a parallel-design, double-blind, proof-of-concept, placebo-controlled randomized clinical trial conducted between September 22, 2021, and August 29, 2022, at the Department of Dermatology, Aarhus University Hospital in Denmark. The study included a 1- to 30-day screening period, a 16-week treatment period, and a 4-week follow-up period. Eligibility criteria included age 18 years or older and moderate to severe hidradenitis suppurativa with 6 or more inflammatory nodules or abscesses in at least 2 distinct anatomic regions. Of 19 patients screened, 15 patients were enrolled in the study. Intention-to-treat analysis was performed.

Interventions

Patients were randomly assigned (2:1) to receive oral RGRN-305, 250-mg tablet, or matching placebo once daily for 16 weeks.

Main Outcomes and Measures

The primary efficacy end point was the percentage of patients achieving Hidradenitis Suppurativa Clinical Response 50 (HiSCR-50) at week 16. Secondary efficacy end points included HiSCR-75 or HiSCR-90, Hidradenitis Suppurativa Physician's Global Assessment, Dermatology Life Quality Index scores, and a pain numeric rating scale. Safety was assessed by adverse events, physical examinations, clinical laboratory measurements, and electrocardiograms.

Results

A total of 15 patients were enrolled, completed the study, and were included in all analyses (10 [67%] female; median age, 29 [IQR, 23-41] years). The primary end point HiSCR-50 at week 16 was achieved by a higher percentage in the RGRN-305 group (60% [6 of 10]) than in the placebo group (20% [1 of 5]). Improvements were also observed across all secondary end points at week 16, including higher rates of the harder-to-reach HiSCR levels; 50% (5 of 10) achieved HiSCR-75 and 30% (3 of 10) achieved HiSCR-90, whereas none of the placebo-treated patients achieved HiSCR-75 or HiSCR-90. RGRN-305 was well tolerated, with no deaths or serious adverse events, and treatment-emergent adverse events were similarly frequent between the RGRN-305 and placebo groups.

Conclusions and Relevance

The findings of this trial suggest that heat shock protein 90 inhibition by RGRN-305 offers a novel mechanism of action in treating hidradenitis suppurativa, warranting further evaluation in larger trials.

Trial Registration

ClinicalTrials.gov Identifier: NCT05286567.

Celastrol attenuates hepatitis C virus translation and inflammatory response in mice by suppressing heat shock protein 90β

Hepatitis C virus (HCV) infection is one of the major factors to trigger a sustained hepatic inflammatory response and hence hepatocellular carcinoma (HCC), but direct-acting-antiviral (DAAs) was not efficient to suppress HCC development. Heat shock protein 90 kDa (HSP90) is highly abundant in different types of cancers, and especially controls protein translation, endoplasmic reticulum stress, and viral replication. In this study we investigated the correlation between the expression levels of HSP90 isoforms and inflammatory response marker NLRP3 in different types of HCC patients as well as the effect of a natural product celastrol in suppression of HCV translation and associated inflammatory response in vivo. We identified that the expression level of HSP90β isoform was correlated with that of NLRP3 in the liver tissues of HCV positive HCC patients (R2 = 0.3867, P < 0.0101), but not in hepatitis B virus-associated HCC or cirrhosis patients. We demonstrated that celastrol (3, 10, 30 μM) dose-dependently suppressed the ATPase activity of both HSP90α and HSP90β, while its anti-HCV activity was dependent on the Ala47 residue in the ATPase pocket of HSP90β. Celastrol (200 nM) halted HCV internal ribosomal entry site (IRES)-mediated translation at the initial step by disrupting the association between HSP90β and 4EBP1. The inhibitory activity of celastrol on HCV RNA-dependent RNA polymerase (RdRp)-triggered inflammatory response also depended on the Ala47 residue of HSP90β. Intravenous injection of adenovirus expressing HCV NS5B (pAde-NS5B) in mice induced severe hepatic inflammatory response characterized by significantly increased infiltration of immune cells and hepatic expression level of Nlrp3, which was dose-dependently ameliorated by pretreatment with celastrol (0.2, 0.5 mg/kg, i.p.). This study reveals a fundamental role of HSP90β in governing HCV IRES-mediated translation as well as hepatic inflammation, and celastrol as a novel inhibitor of HCV translation and associated inflammation by specifically targeting HSP90β, which could be developed as a lead for the treatment of HSP90β positive HCV-associated HCC.

Heat shock protein 90 C-terminal inhibitor PNSA promotes anticancer immunology of CD8+ T cells

Penisuloxazin A (PNSA), a new compound from the fungus, is a novel C-terminal Hsp90 inhibitor reported by us before. It has been reported to possess antitumor activity and suppresses metastasis of breast cancer cells. However, the influence of PNSA on T cells is not fully understood. Here, we found that PNSA was much less toxic to lymphocytes than to tumor cells and it had no significant effect on populations of CD3+, CD4+ and CD8+ T lymphocytes. We discovered that PNSA directly enhanced the killing capacities of the CD8+ T and CD3+CD25- to CT26 cells, but not that of CD3+ cells due to the increase of Treg cells. What's more, PNSA pretreated tumor cells increase the sensitivity to CD8+ T cells mainly through the degradation of client protein of Hsp90 and declination of PD-L1 expression. Eventually, PNSA enhanced the killing ability of CD8+ and CD3+ T cells by simultaneously acting on lymphocytes and cancer cells. In vivo experiments, PNSA exhibited inhibition effects in the colon adenocarcinoma with increase of CD8 T cell infiltration in tumor tissues. All these results indicate that the novel Hsp90 C-terminal inhibitor-PNSA can promote lytic T cell immunological function to improve anticancer effect of PNSA, which provides a better foundation for anticancer drug development of PNSA in future.

Heat shock protein 90 inhibitor RGRN-305 potently attenuates skin inflammation

Introduction

Chronic inflammatory skin diseases may have a profound negative impact on the quality of life. Current treatment options may be inadequate, offering an unsatisfactory response or side effects. Therefore, ongoing efforts exist to identify novel effective and safe treatments. Heat shock protein (HSP) 90 is a chaperone that promotes the activity of a wide range of client proteins including key proinflammatory molecules involved in aberrant inflammation. Recently, a proof-of-concept clinical trial of 13 patients suggested that RGRN-305 (an HSP90 inhibitor) may be an oral treatment for psoriasis. However, HSP90 inhibition may be a novel therapeutic approach extending beyond psoriasis to include multiple immune-mediated inflammatory skin diseases.

Methods

This study aimed to investigate (i) the anti-inflammatory effects and mechanisms of HSP90 inhibition and (ii) the feasibility of topical RGRN-305 administration (new route of administration) in models of inflammation elicited by 12-O-tetradecanoylphorbol-13-acetate (TPA) in primary human keratinocytes and mice (irritative dermatitis murine model).

Results/Discussion

In primary human keratinocytes stimulated with TPA, a Nanostring® nCounter gene expression assay demonstrated that HSP90 inhibition with RGRN-305 suppressed many proinflammatory genes. Furthermore, when measured by quantitative real-time polymerase chain reaction (RT-qPCR), RGRN-305 significantly reduced the gene expression of TNF, IL1B, IL6 and CXCL8. We next demonstrated that topical RGRN-305 application significantly ameliorated TPA-induced skin inflammation in mice. The increase in ear thickness (a marker of inflammation) was significantly reduced (up to 89% inhibition). In accordance, RT-qPCR of the ear tissue demonstrated that RGRN-305 robustly reduced the gene expression of proinflammatory markers (Tnf, Il1b, Il6, Il17A and Defb4). Moreover, RNA sequencing revealed that RGRN-305 mitigated TPA-induced alterations in gene expression and suppressed genes implicated in inflammation. Lastly, we discovered that the anti-inflammatory effects were mediated, at least partly, by suppressing the activity of NF-κB, ERK1/2, p38 MAPK and c-Jun signaling pathways, which are consistent with previous findings in other experimental models beyond skin inflammation. In summary, HSP90 inhibition robustly suppressed TPA-induced inflammation by targeting key proinflammatory cytokines and signaling pathways. Our findings suggest that HSP90 inhibition may be a novel mechanism of action for treating immune-mediated skin disease beyond psoriasis, and it may be a topical treatment option.

Water Networks Repopulate Protein-Ligand Interfaces with Temperature

High-resolution crystal structures highlight the importance of water networks in protein-ligand interactions. However, as these are typically determined at cryogenic temperature, resulting insights may be structurally precise but not biologically accurate. By collecting 10 matched room-temperature and cryogenic datasets of the biomedical target Hsp90α, we identified changes in water networks that impact protein conformations at the ligand binding interface. Water repositioning with temperature repopulates protein ensembles and ligand interactions. We introduce Flipper conformational barcodes to identify temperature-sensitive regions in electron density maps. This revealed that temperature-responsive states coincide with ligand-responsive regions and capture unique binding signatures that disappear upon cryo-cooling. Our results have implications for discovering Hsp90 selective ligands, and, more generally, for the utility of hidden protein and water conformations in drug discovery.

Integrating 3D genomic and epigenomic data to enhance target gene discovery and drug repurposing in transcriptome-wide association studies

Transcriptome-wide association studies (TWAS) are popular approaches to test for association between imputed gene expression levels and traits of interest. Here, we propose an integrative method PUMICE (Prediction Using Models Informed by Chromatin conformations and Epigenomics) to integrate 3D genomic and epigenomic data with expression quantitative trait loci (eQTL) to more accurately predict gene expressions. PUMICE helps define and prioritize regions that harbor cis-regulatory variants, which outperforms competing methods. We further describe an extension to our method PUMICE +, which jointly combines TWAS results from single- and multi-tissue models. Across 79 traits, PUMICE + identifies 22% more independent novel genes and increases median chi-square statistics values at known loci by 35% compared to the second-best method, as well as achieves the narrowest credible interval size. Lastly, we perform computational drug repurposing and confirm that PUMICE + outperforms other TWAS methods.

Heat Shock Proteins Alterations in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory and autoimmune disease characterized by the attack of the immune system on the body's healthy joint lining and degeneration of articular structures. This disease involves an increased release of inflammatory mediators in the affected joint that sensitize sensory neurons and create a positive feedback loop to further enhance their release. Among these mediators, the cytokines and neuropeptides are responsible for the crippling pain and the persistent neurogenic inflammation associated with RA. More importantly, specific proteins released either centrally or peripherally have been shown to play opposing roles in the pathogenesis of this disease: an inflammatory role that mediates and increases the severity of inflammatory response and/or an anti-inflammatory and protective role that modulates the process of inflammation. In this review, we will shed light on the neuroimmune function of different members of the heat shock protein (HSPs) family and the complex manifold actions that they exert during the course of RA. Specifically, we will focus our discussion on the duality in the mechanism of action of Hsp27, Hsp60, Hsp70, and Hsp90.

HSP90 Inhibitor 17-AAG Attenuates Nucleus Pulposus Inflammation and Catabolism Induced by M1-Polarized Macrophages

Overactivated inflammation and catabolism induced by proinflammatory macrophages are involved in the pathological processes of intervertebral disc (IVD) degeneration (IVDD). Our previous study suggested the protective role of inhibiting heat shock protein 90 (HSP90) in IVDD, while the underlying mechanisms need advanced research. The current study investigated the effects of HSP90 inhibitor 17-AAG on nucleus pulposus (NP) inflammation and catabolism induced by M1-polarized macrophages. Immunohistochemical staining of degenerated human IVD samples showed massive infiltration of macrophages, especially M1 phenotype, as well as elevated levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α and matrix metalloproteinase (MMP)13. The conditioned medium (CM) of inflamed NP cells (NPCs) enhanced M1 polarization of macrophages, while the CM of M1 macrophages but not M2 macrophages promoted the expression of inflammatory factors and matrix proteases in NPCs. Additionally, we found that 17-AAG could represent anti-inflammatory and anti-catabolic effects by modulating both macrophages and NPCs. On the one hand, 17-AAG attenuated the pro-inflammatory activity of M1 macrophages via inhibiting nuclear factor-κB (NF-κB) pathway and mitogen-activated protein kinase (MAPK) pathways. On the other hand, 17-AAG dampened M1-CM-induced inflammation and catabolism in NPCs by upregulating HSP70 and suppressing the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway. Moreover, both in vitro IVD culture models and murine disc puncture models supported that 17-AAG treatment decreased the levels of inflammatory factors and matrix proteases in IVD tissues. In conclusion, HSP90 inhibitor 17-AAG attenuates NP inflammation and catabolism induced by M1 macrophages, suggesting 17-AAG as a promising candidate for IVDD treatment.

HSP90 inhibitor RGRN-305 for oral treatment of plaque type psoriasis: efficacy, safety and biomarker results in an open-label proof-of-concept study

BACKGROUND

HSP90 is a downstream regulator of tumor necrosis factor α (TNFα) and interleukin (IL)-17A signaling and may therefore serve as a novel target in the treatment of psoriasis.

OBJECTIVE

This phase 1b proof-of-concept study was undertaken to evaluate the safety and efficacy of a novel HSP90 inhibitor (RGRN-305) in the treatment of plaque psoriasis.

METHODS

An open-label, single-arm, dose-selection, single-center proof-of-concept study. Patients with plaque psoriasis were treated with 250 mg or 500 mg RGRN-305 daily for 12 weeks. Efficacy was evaluated clinically using Psoriasis Area and Severity Index (PASI), body surface area (BSA), and Physician Global Assessment (PGA) scores and by Dermatology Life Quality Index (DLQI). Skin biopsies collected at baseline and at 4, 8, and 12 weeks after treatment start were used for immunohistochemical staining and for gene expression analysis. Safety was monitored via laboratory tests, vital signs, ECG, and physical examinations.

RESULTS

Six of the eleven patients completing the study responded to RGRN-305 with a PASI improvement between 71% and 94%, whereas five patients were considered nonresponders with a PASI response < 50%. No severe adverse events were reported. Four of seven patients treated with 500 mg RGRN-305 daily experienced a mild to moderate exanthematous drug induced eruption due to study treatment. Two patients chose to discontinue the study due to this exanthematous eruption. RGRN-305 treatment resulted in pronounced inhibition of the IL-23, TNFα, and IL-17A signaling pathways and normalization of both histological changes and psoriatic lesion gene expression profiles in patients responding to treatment.

CONCLUSION

Treatment with RGRN-305 showed an acceptable safety, especially in the low-dose group, and was associated with clinically meaningful improvement in a subset of patients with plaque psoriasis, indicating that HSP90 may serve as a novel future target in psoriasis treatment.

The HSP90 Inhibitor, 17-AAG, Influences the Activation and Proliferation of T Lymphocytes via AKT/GSK3β Signaling in MRL/lpr Mice

Objective

To explore the molecular mechanism of 17-AAG in the treatment of systemic lupus erythematosus (SLE), and the effects of the heat shock protein 90 (HSP90) inhibitor 17-AAG on the activation and proliferation of lymphocytes and the AKT/GSK3β signaling pathway in MRL/lpr mice were detected.

Methods

MRL/lpr mice were randomly divided into the control group and the experimental group. The experimental group was injected intraperitoneally with 17-AAG, and T lymphocytes were separated by magnetic beads. Lymphocyte proliferation was detected by MTT and flow cytometry (FCM), and the expression of the HSP90 protein and PI3K/AKT signaling pathway-related proteins was detected by Western blotting. Renal histopathology and immune complex deposition were also observed in both groups.

Results

Immune complex deposition and inflammation decreased in kidneys from MRL/lpr mice in the experimental group. HSP90 protein expression, T lymphocyte proliferation and phosphorylated AKT and GSK3β levels also decreased in the experimental group.

Conclusion

17-AAG can inhibit the activation and proliferation of T lymphocytes and downregulate the AKT/GSK3β signaling pathway, which may be relevant for the treatment of SLE.

Inhibition of the NLRP3 inflammasome by HSP90 inhibitors

Excessive and dysregulated inflammation is known to contribute to disease progression. HSP90 is an intracellular chaperone known to regulate inflammatory processes including the NLRP3 inflammasome and secretion of the pro‐inflammatory cytokine interleukin(IL)‐1β. Here, primarily using an in vitro inflammasome ASC speck assay, and an in vivo model of murine peritonitis, we tested the utility of HSP90 inhibitors as anti‐inflammatory molecules. We report that the HSP90 inhibitor EC144 effectively inhibited inflammatory processes including priming and activation of NLRP3 in vitro and in vivo. A specific inhibitor of the β HSP90 isoform was ineffective suggesting the importance of the α isoform in inflammatory signalling. EC144 inhibited IL‐1β and IL‐6 in vivo when administered orally, and was brain‐penetrant. These data suggest that HSP90 inhibitors may be useful for targeting inflammation in diverse diseases that are worsened by the presence of inflammation.

Heat shock protein 90 and NFkB levels in serum and urine in patients with chronic glomerulonephritis

Heat shock proteins play an important role in immune inflammation and the formation and restoration of proteins. In recent years, the importance of heat shock protein 90 (Hsp90) in the activation of immune inflammation through nuclear factor kB (NFkB) has been discussed. To assess the activation of the Hsp90-NFkB system by measuring serum and urinary levels in patients with chronic glomerulonephritis (CGN). This study included 32 patients with active forms of CGN and 14 patients with Fabry nephropathy. The control group included 10 healthy individuals. Twenty-one out of 32 CGN patients had nephrotic syndrome (NS). Eleven out of 32 CGN patients had proteinuria levels from 1 to 3 g/day without nephrotic syndrome. A total of 17 patients had renal dysfunction (estimated glomerular filtration rate < 60 ml/min/1.73m2). Fourteen patients with Fabry nephropathy had proteinuria without nephrotic syndrome. Serum and urine HSP-90 and NFkB p65 levels were determined using an enzyme-linked immunosorbent assay. The levels of HSP-90 and NFkB in the serum of patients with CGN were significantly higher than in healthy individuals and patients with Fabry nephropathy. In patients with Fabry nephropathy, the HSP-90 and NFkB levels in the urine and serum did not significantly differ from those in the control subjects. Serum Hsp90 levels were significantly higher in the CGN patients with NS than in patients without NS, as well as in patients with normal renal function compared with patients with an eGFR < 60 ml/min/1.73 m2 and patients with tubulo-interstitial fibrosis. Higher levels of HSP-90 and NFkB in serum were observed in patients with nephrotic forms of CGN, including focal segmental glomerulosclerosis, minimal change disease and membranous nephropathy. There were no correlations between the clinical signs of CGN and urinary HSP90/NFkB levels. Activation of the HSP-90-NFkB system, which is directly involved in the development of immune inflammation in CGN, was found in patients with an active course of CGN, especially in those with nephrotic syndrome.

Combining Tumor Microenvironment Modulating Nanoparticles with Doxorubicin to Enhance Chemotherapeutic Efficacy and Boost Antitumor Immunity

BACKGROUND

Tumor microenvironment (TME) and associated multiple factors are found to contribute to the failures in cancer therapies, including chemo- and immunotherapy. Here we report a new multimodal strategy that uses a bioreactive multifunctional hybrid polymer-lipid encapsulated manganese dioxide nanoparticle (PLMD NP) system to remodel the TME, suppress drug resistance factors, reverse immunosuppressive conditions, and enhance chemotherapy efficacy.

METHODS

The influence of PLMD NPs on enhancing cellular uptake in EMT6 mouse breast cancer cells and tumor penetration of doxorubicin (DOX) in EMT6 orthotopic breast tumor mouse model was evaluated using confocal microscopy (n = 3-4). Immunohistochemistry was employed to examine the effect of PLMD NPs on downregulating hypoxia-induced drug resistance proteins and anticancer activity of DOX (n = 3-4). The efficacy of the combination therapy with PLMD NPS and DOX was assessed in murine EMT6 (n = 15-23) and 4T1 (n = 7) orthotopic breast tumor mouse models. Rechallenge and splenocyte transfer were performed to validate the stimulation of adaptive tumor immunity in the surviving mice.

RESULTS

PLMD NPs enhanced intratumoral penetration and efficacy of DOX, and reduced intratumoral expression of P-glycoprotein, p53, and carbonic anhydrase IX by 74.5%, 38.0%, and 58.8% vs saline control, respectively. Combination treatment with PLMD NPs and DOX increased the number of tumor-infiltrated CD8+ T cells and resulted in up to 60.0% complete tumor regression. Of naïve mice (n = 7) that received splenocytes from the PLMD+DOX-treated surviving mice, 57.1% completely suppressed tumor growth whereas 100% of mice that received splenocytes from DOX-treated mice (n = 3) and the control group (n = 7) showed rapid tumor growth.

CONCLUSIONS

The clinically suitable PLMD NPs can effectively downregulate TME-associated drug resistance and immunosuppression. The combination therapy with PLMD NPs and DOX is a multimodal and translational treatment approach for enhancing chemotherapeutic efficacy and boosting antitumor immunity.

trans, trans-2,4-Decadienal, a lipid peroxidation product, induces inflammatory responses via Hsp90- or 14-3-3ζ-dependent mechanisms

Peroxidation of polyunsaturated fatty acids leads to the formation of a large array of lipid-derived electrophiles (LDEs), many of which are important signaling molecules involved in the pathogenesis of human diseases. Previous research has shown that one of such LDEs, trans, trans-2,4-decadienal (tt-DDE), increases inflammation, however, the underlying mechanisms are not well understood. Here we used click chemistry-based proteomics to identify the cellular targets which are required for the pro-inflammatory effects of tt-DDE. We found that treatment with tt-DDE increased cytokine production, JNK phosphorylation, and activation of NF-κB signaling in macrophage cells, and increased severity of dextran sulfate sodium (DSS)-induced colonic inflammation in mice, demonstrating its pro-inflammatory effects in vitro and in vivo. Using click chemistry-based proteomics, we found that tt-DDE directly interacts with Hsp90 and 14-3-3ζ, which are two important proteins involved in inflammation and tumorigenesis. Furthermore, siRNA knockdown of Hsp90 or 14-3-3ζ abolished the pro-inflammatory effects of tt-DDE in macrophage cells. Together, our results support that tt-DDE increases inflammatory responses via Hsp90- and 14-3-3ζ-dependent mechanisms.

HSP90: Enabler of Cancer Adaptation

The stability and function of many oncogenic mutant proteins depend on heat shock protein 90 (HSP90). This unique activity has inspired the exploration of HSP90 as an anticancer target for over two decades. Unfortunately, while clinical trials of highly optimized HSP90 inhibitors have demonstrated modest benefit for patients with advanced cancers, most commonly stabilization of disease, no HSP90 inhibitor has demonstrated sufficient efficacy to achieve FDA approval to date. This review discusses potential reasons for the limited success of these agents and how our increasingly sophisticated understanding of HSP90 suggests alternative, potentially more effective strategies for targeting it to treat cancers. First, we focus on insights gained from model organisms that suggest a fundamental role for HSP90 in supporting the adaptability and heterogeneity of cancers, key factors underlying their ability to evolve and acquire drug resistance. Second, we examine how HSP90’s role in promoting the stability of mutant proteins might be targeted in genetically unstable tumor cells to reveal their aberrant, foreign proteome to the immune system. Both of these emerging aspects of HSP90 biology suggest that the most effective use of HSP90 inhibitors may not be at high doses with the intent to kill cancer cells, but rather in combination with other molecularly targeted therapies at modest, non-heat shock-inducing exposures that limit the adaptive capacity of cancers.

The Role of Heat Shock Proteins in Regulating Receptor Signal Transduction

Heat shock proteins (Hsp) are a class of stress-inducible proteins that mainly act as molecular protein chaperones. This chaperone activity is diverse, including assisting in nascent protein folding and regulating client protein location and translocation within the cell. The main proteins within the Hsp family, particularly Hsp70 and Hsp90, also have a highly diverse and numerous set of protein clients, which when combined with the high expression levels of Hsp proteins (2%-6% of total protein content) establishes these molecules as "central regulators" of cell protein physiology. Among the client proteins, Hsps regulate numerous signal-transduction and receptor-regulatory kinases, and indeed directly regulate some receptors themselves. This also makes the Hsps, particularly Hsp90, central regulators of signal-transduction machinery, with important impacts on endogenous and drug ligand responses. Among these roles, Hsp90 in particular acts to maintain mature signaling kinases in a metastable conformation permissive for signaling activation. In this review, we will focus on the roles of the Hsps, with a special focus on Hsp90, in regulating receptor signaling and subsequent physiologic responses. We will also explore potential means to manipulate Hsp function to improve receptor-targeted therapies. Overall, Hsps are important regulators of receptor signaling that are receiving increasing interest and exploration, particularly as Hsp90 inhibitors progress toward clinical approval for the treatment of cancer. Understanding the complex interplay of Hsp regulation of receptor signaling may provide important avenues to improve patient treatment.

Inhibition of HSP90β by ganetespib blocks the microglial signalling of evoked pro-inflammatory responses to heat shock

Although microglial reaction to heat shock is considered to be protective, heat shock is still a potential hazard caused by high temperatures. Recent studies indicate that the inhibition of the 90-kDa heat shock protein (HSP90) increasing the protective heat shock response and suppressing inflammatory signalling pathways in several diseases. Nevertheless, the effects of heat shock on microglial pro-inflammatory responses are not completely identical. Here, we aim to investigate the effect of the HSP90 inhibitor ganetespib on microglial pro-inflammatory responses following heat shock. HSP90 isoforms were determined by transfecting N9 microglial cells (N9 cells) with enzymatically prepared siRNA (esiRNAs). We found that heat shock significantly increased the secretion of tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6 and nitric oxide (NO), and the phosphorylation of extracellular signal-regulated kinase (ERK), Janus-activated kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (IκB-α) and p65 nuclear factor kappa-light-chain-enhancer of activated B cells (p65 NF-κB) in N9 cells. These increases, except for phospho-p65, were attenuated efficiently in a dose-dependent manner by ganetespib pretreatment. Furthermore, the suppression of heat shock-evoked cytokines and NO production, and the phosphorylation of ERK, JAK2 and STAT3 in cytosols and/or nuclei were also observed by administering esiRNA HSP90β, but not HSP90α, in heat shock-treated N9 cells. Taken together, our findings demonstrate that the HSP90 inhibitor ganetespib blocks pro-inflammatory responses in heat shock-treated N9 cells via a signalling mechanism involving HSP90β and STAT3.

The Combined Use of in Silico, in Vitro, and in Vivo Analyses to Assess Anti-cancerous Potential of a Bioactive Compound from Cyanobacterium Nostoc sp. MGL001

Escalating incidences of cancer, especially in developed and developing countries, demand evaluation of potential unexplored natural drug resources. Here, anticancer potential of 9-Ethyliminomethyl-12-(morpholin-4-ylmethoxy)-5,8,13,16-tetraaza -hexacene-2,3-dicarboxylic acid (EMTAHDCA) isolated from fresh water cyanobacterium Nostoc sp. MGL001 was screened through in silico, in vitro, and in vivo studies. For in silico analysis, EMTAHDCA was selected as ligand and 11 cancer related proteins (Protein Data Bank ID: 1BIX, 1NOW, 1TE6, 2RCW, 2UVL, 2VCJ, 3CRY, 3HQU, 3NMQ, 5P21, and 4B7P) which are common targets of various anticancer drugs were selected as receptors. The results obtained from in silico analysis showed that EMTAHDCA has strong binding affinity for all the 11 target protein receptors. The ability of EMTAHDCA to bind active sites of cancer protein targets indicated that it is functionally similar to commercially available anticancer drugs. For assessing cellular metabolic activities, in vitro studies were performed by using calorimetric assay viz. 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT). Results showed that EMTAHDCA induced significant cytotoxic response against Dalton's lymphoma ascites (DLA) cells in a dose and time dependent manner with an inhibitory concentration (IC50) value of 372.4 ng/mL after 24 h of incubation. However, in case of normal bone marrow cells, the EMTAHDCA did not induce cytotoxicity as the IC50 value was not obtained even with higher dose of 1,000 ng/mL EMTAHDCA. Further, in vivo studies revealed that the median life span/survival days of tumor bearing mice treated with EMTAHDCA increased significantly with a fold change of ~1.9 and 1.81 corresponding to doses of 5 and 10 mg/kg body weight (B.W.) of EMTAHDCA respectively, as compared to the DL group. Our results suggest that 5 mg/kg B.W. is effective since the dose of 10 mg/kg B.W. did not show any significant difference as compared to 5 mg/kg B.W. Taken together, our findings based on in silico, in vitro, and in vivo analyses suggest that EMTAHDCA has potential anticancer effects, and thus, can be considered for cancer treatment.

Role of aryl hydrocarbon receptor in mesenchymal stromal cell activation: A minireview

Mesenchymal stromal cells (MSCs) possess great therapeutic advantages due to their ability to produce a diverse array of trophic/growth factors related to cytoprotection and immunoregulation. MSC activation via specific receptors is a crucial event for these cells to exert their immunosuppressive response. The aryl-hydrocarbon receptor (AhR) is a sensitive molecule for external signals and it is expressed in MSCs and, upon positive activation, may potentially regulate the MSC-associated immunomodulatory function. Consequently, signalling pathways linked to AhR activation can elucidate some of the molecular cascades involved in MSC-mediated immunosuppression. In this minireview, we have noted some important findings concerning MSC regulation via AhR, highlighting that its activation is associated with improvement in migration and immunoregulation, as well as an increase in pro-regenerative potential. Thus, AhR-mediated MSC activation can contribute to new perspectives on MSC-based therapies, particularly those directed at immune-associated disorders.

Drug-Induced HSP90 Inhibition Alleviates Pain in Monoarthritic Rats and Alters the Expression of New Putative Pain Players at the DRG

Purinergic receptors (P2XRs) have been widely associated with pain states mostly due to their involvement in neuron-glia communication. Interestingly, we have previously shown that satellite glial cells (SGC), surrounding dorsal root ganglia (DRG) neurons, become activated and proliferate during monoarthritis (MA) in the rat. Here, we demonstrate that P2X7R expression increases in ipsilateral DRG after 1 week of disease, while P2X3R immunoreactivity decreases. We have also reported a significant induction of the activating transcriptional factor 3 (ATF3) in MA. In this study, we show that ATF3 knocked down in DRG cell cultures does not affect the expression of P2X7R, P2X3R, or glial fibrillary acidic protein (GFAP). We suggest that P2X7R negatively regulates P2X3R, which, however, is unlikely mediated by ATF3. Interestingly, we found that ATF3 knockdown in vitro induced significant decreases in the heat shock protein 90 (HSP90) expression. Thus, we evaluated in vivo the involvement of HSP90 in MA and demonstrated that the HSP90 messenger RNA levels increase in ipsilateral DRG of inflamed animals. We also show that HSP90 is mostly found in a cleaved form in this condition. Moreover, administration of a HSP90 inhibitor, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), attenuated MA-induced mechanical allodynia in the first hours. The drug also reversed the HSP90 upregulation and cleavage. 17-DMAG seemed to attenuate glial activation and neuronal sensitization (as inferred by downregulation of GFAP and P2X3R in ipsilateral DRG) which might correlate with the observed pain alleviation. Our data indicate a role of HSP90 in MA pathophysiology, but further investigation is necessary to clarify the underlying mechanisms.

Anti-Hsp90 therapy in autoimmune and inflammatory diseases: a review of preclinical studies

Heat shock protein 90 (Hsp90), a 90-kDa molecular chaperone, is responsible for biological activities of key signaling molecules (clients) such as protein kinases, ubiquitin ligases, steroid receptors, cell cycle regulators, and transcription factors regulating various cellular processes, including growth, survival, differentiation, and apoptosis. Because Hsp90 is also involved in stabilization of oncogenic 'client' proteins, its specific chaperone activity blockers are currently being tested as anticancer agents in advanced clinical trials. Recent in vitro and in vivo studies have shown that Hsp90 is also involved in activation of innate and adaptive cells of the immune system. For these reasons, pharmacological inhibition of Hsp90 has been evaluated in murine models of autoimmune and inflammatory diseases. This mini-review summarizes current knowledge of the effects of Hsp90 inhibitors on autoimmune and inflammatory diseases' features and is based solely on preclinical studies.

HSP90 and Immune Modulation in Cancer

Heat-shock protein 90 (HSP90) is a highly conserved molecular chaperone that plays prominent functional roles in nearly all aspects of cell biology. As a chaperone, it interacts with literally hundreds of "clients," many of which are important drivers, regulators, and promoters of cancer. Thus, HSP90 is a high-value target in the development of anticancer therapeutics. Despite its popularity, our overall knowledge of HSP90 in immune function has lagged behind its well-recognized tumor-supportive roles. The use of inhibitors of HSP90 as chemical biological probes has been invaluable in revealing important roles for the chaperone in multiple aspects of immune function. Given this critical link, we must now consider the question of how immune outcomes may be affected by the HSP90 inhibitors currently in clinical development for the treatment of cancer. This chapter will review some of the immunological aspects of HSP90 function in terms of its intracellular and extracellular roles in antigen presentation, immune effector cell tasks, and regulation of inflammatory processes. This review will further examine the value of HSP90 inhibitors within the context of cancer immunotherapy and will discuss how these drugs might be optimally utilized in combination with immune stimulatory approaches against cancer.

Update on pathogenesis and predictors of response of therapeutic strategies used in inflammatory bowel disease

The search for biomarkers that characterize specific aspects of inflammatory bowel disease (IBD), has received substantial interest in the past years and is moving forward rapidly with the help of modern technologies. Nevertheless, there is a direct demand to identify adequate biomarkers for predicting and evaluating therapeutic response to different therapies. In this subset, pharmacogenetics deserves more attention as part of the endeavor to provide personalized medicine. The ultimate goal in this area is the adjustment of medication for a patient’s specific genetic background and thereby to improve drug efficacy and safety rates. The aim of the following review is to utilize the latest knowledge on immunopathogenesis of IBD and update the findings on the field of Immunology and Genetics, to evaluate the response to the different therapies. In the present article, more than 400 publications were reviewed but finally 287 included based on design, reproducibility (or expectancy to be reproducible and translationable into humans) or already measured in humans. A few tests have shown clinical applicability. Other, i.e., genetic associations for the different therapies in IBD have not yet shown consistent or robust results. In the close future it is anticipated that this, cellular and genetic material, as well as the determination of biomarkers will be implemented in an integrated molecular diagnostic and prognostic approach to manage IBD patients.

HSP90 and HSP70: Implication in Inflammation Processes and Therapeutic Approaches for Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) are clonal stem cell disorders that lead to the excessive production of one or more blood cell lineages. It has been reported that, in most MPN, inflammatory cytokines are frequently increased, indicating that inflammation plays a crucial role in these disorders. Heat shock proteins (HSP) are induced in response to many stressful conditions from heat shock to hypoxia and inflammation. Besides their chaperone and cytoprotective functions, HSPs are key players during inflammation, hence the term “chaperokine.” Through their chaperone activity, HSP90, a stabilizer of many oncogenes (e.g., JAK2), and HSP70, a powerful antiapoptotic chaperone, tightly regulate Nuclear Factor-kappa B signalling, a critical pathway in mediating inflammatory responses. In light of this potential, several HSP90 inhibitors have been generated as anticancer agents able to degrade oncogenes. As it turns out, however, these drugs are also potent inhibitors of the inflammatory response in various diseases. Given the chaperone potential of HSP70 and the fact that HSP90 inhibitors induce HSP70, interest in HSP70 inhibitors is also increasing. Here, we focus on the implication of HSP90 and HSP70 in inflammatory responses and on the emergence of new therapeutic approaches in MPN based on HSP inhibitors.

Gedunin Binds to Myeloid Differentiation Protein 2 and Impairs Lipopolysaccharide-Induced Toll-Like Receptor 4 Signaling in Macrophages

Recognition of bacterial lipopolysaccharide (LPS) by innate immune system is mediated by the cluster of differentiation 14/Toll-like receptor 4/myeloid differentiation protein 2 (MD-2) complex. In this study, we investigated the modulatory effect of gedunin, a limonoid from species of the Meliaceae family described as a heat shock protein Hsp90 inhibitor, on LPS-induced response in immortalized murine macrophages. The pretreatment of wild-type (WT) macrophages with gedunin (0.01-100 µM, noncytotoxic concentrations) inhibited LPS (50 ng/ml)-induced calcium influx, tumor necrosis factor-α, and nitric oxide production in a concentration-dependent manner. The selective effect of gedunin on MyD88-adapter-like/myeloid differentiation primary response 88- and TRIF-related adaptor molecule/TIR domain-containing adapter-inducing interferon-β-dependent signaling pathways was further investigated. The pretreatment of WT, TIR domain-containing adapter-inducing interferon-β knockout, and MyD88 adapter-like knockout macrophages with gedunin (10 µM) significantly inhibited LPS (50 ng/ml)-induced tumor necrosis factor-α and interleukin-6 production, at 6 hours and 24 hours, suggesting that gedunin modulates a common event between both signaling pathways. Furthermore, gedunin (10 µM) inhibited LPS-induced prostaglandin E2 production, cyclooxygenase-2 expression, and nuclear factor κB translocation into the nucleus of WT macrophages, demonstrating a wide-range effect of this chemical compound. In addition to the ability to inhibit LPS-induced proinflammatory mediators, gedunin also triggered anti-inflammatory factors interleukin-10, heme oxygenase-1, and Hsp70 in macrophages stimulated or not with LPS. In silico modeling studies revealed that gedunin efficiently docked into the MD-2 LPS binding site, a phenomenon further confirmed by surface plasmon resonance. Our results reveal that, in addition to Hsp90 modulation, gedunin acts as a competitive inhibitor of LPS, blocking the formation of the Toll-like receptor 4/MD-2/LPS complex.

The HSP90 Inhibitor Ganetespib Alleviates Disease Progression and Augments Intermittent Cyclophosphamide Therapy in the MRL/lpr Mouse Model of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex, systemic autoimmune disease with a diverse range of immunological and clinical manifestations. The introduction of broad spectrum immunosuppressive therapies and better management of acute disease exacerbations have improved outcomes for lupus patients over recent years. However, these regimens are burdened by substantial toxicities and confer significantly higher risks of infection, thus there remains a significant and unmet medical need for alternative treatment options, particularly those with improved safety profiles. Heat shock protein 90 (HSP90) is a ubiquitously expressed molecular chaperone that acts as an important modulator of multiple innate and adaptive inflammatory processes. Of note, accumulating clinical and experimental evidence has implicated a role for HSP90 in the pathogenesis of SLE. Here we evaluated the potential of HSP90 as a therapeutic target for this disease using the selective small molecule inhibitor ganetespib in the well-characterized MRL/lpr autoimmune mouse model. In both the prophylactic and therapeutic dosing settings, ganetespib treatment promoted dramatic symptomatic improvements in multiple disease parameters, including suppression of autoantibody production and the preservation of renal tissue integrity and function. In addition, ganetespib exerted profound inhibitory effects on disease-related lymphadenopathy and splenomegaly, and reduced pathogenic T and B cell lineage populations in the spleen. Ganetespib monotherapy was found to be equally efficacious and tolerable when compared to an effective weekly dosing regimen of the standard-of-care immunosuppressive agent cyclophosphamide. Importantly, co-treatment of ganetespib with a sub-optimal, intermittent dosing schedule of cyclophosphamide resulted in superior therapeutic indices and maximal disease control. These findings highlight the potential of HSP90 inhibition as an alternative, and potentially complementary, strategy for therapeutic intervention in SLE. Such approaches may have important implications for disease management, particularly for limiting or preventing treatment-related toxicities, a major confounding factor in current SLE therapy.

Targeting Heat-Shock Protein 90 (HSP90) as a Complementary Strategy to Immune Checkpoint Blockade for Cancer Therapy

The demonstration that immune checkpoint blockade can meaningfully improve outcomes for cancer patients has revolutionized the field of immuno-oncology. New biologic agents targeting specific checkpoints have shown remarkable durability in terms of patient response and, importantly, exhibit clinical activity across a range of human malignancies, including many that have traditionally proven refractory to other immunotherapies. In this rapidly evolving area, a key consideration relates to the identification of novel combinatorial strategies that exploit existing or investigational cancer therapies in order to optimize patient outcomes and the proportion of individuals able to derive benefit from this approach. In this regard, heat-shock protein 90 (HSP90) represents an important emerging target for cancer therapy because its inactivation results in the simultaneous blockade of multiple signaling pathways and can sensitize tumor cells to other anticancer agents. Within the context of immunology, HSP90 plays a dual regulatory role, with its functional inhibition resulting in both immunosuppressive and immunostimulatory effects. In this Cancer Immunology at the Crossroads overview, the anticancer activity profile of targeted HSP90 inhibitors is discussed along with their paradoxical roles in immunology. Overall, we explore the rationale for combining the modalities of HSP90 inhibition and immune checkpoint blockade in order to augment the antitumor immune response in cancer.

Vibsanin B preferentially targets HSP90β, inhibits interstitial leukocyte migration, and ameliorates experimental autoimmune encephalomyelitis

Interstitial leukocyte migration plays a critical role in inflammation and offers a therapeutic target for treating inflammation-associated diseases such as multiple sclerosis. Identifying small molecules to inhibit undesired leukocyte migration provides promise for the treatment of these disorders. In this study, we identified vibsanin B, a novel macrocyclic diterpenoid isolated from Viburnum odoratissimum Ker-Gawl, that inhibited zebrafish interstitial leukocyte migration using a transgenic zebrafish line (TG:zlyz-enhanced GFP). We found that vibsanin B preferentially binds to heat shock protein (HSP)90β. At the molecular level, inactivation of HSP90 can mimic vibsanin B's effect of inhibiting interstitial leukocyte migration. Furthermore, we demonstrated that vibsanin B ameliorates experimental autoimmune encephalomyelitis in mice with pathological manifestation of decreased leukocyte infiltration into their CNS. In summary, vibsanin B is a novel lead compound that preferentially targets HSP90β and inhibits interstitial leukocyte migration, offering a promising drug lead for treating inflammation-associated diseases.

HSP90 inhibition suppresses lipopolysaccharide-induced lung inflammation in vivo

Inflammation is an important component of cancer diathesis and treatment-refractory inflammation is a feature of many chronic degenerative lung diseases. HSP90 is a 90kDa protein which functions as an ATP-dependent molecular chaperone that regulates the signalling conformation and expression of multiple protein client proteins especially oncogenic mediators. HSP90 inhibitors are in clinical development as cancer therapies but the myeleosuppressive and neutropenic effect of first generation geldanamycin-class inhibitors has confounded studies on the effects on HSP90 inhibitors on inflammation. To address this we assessed the ability of Ganetespib, a non-geldanamycin HSP90 blocker, to suppress lipopolysaccharide (LPS)-induced cellular infiltrates, proteases and inflammatory mediator and transcriptional profiles. Ganetespib (10-100 mg/kg, i.v.) did not directly cause myelosuppression, as assessed by video micrography and basal blood cell count, but it strongly and dose-dependently suppressed LPS-induced neutrophil mobilization into blood and neutrophil- and mononuclear cell-rich steroid-refractory lung inflammation. Ganetespib also suppressed B cell and NK cell accumulation, inflammatory cytokine and chemokine induction and MMP9 levels. These data identify non-myelosuppresssive HSP90 inhibitors as potential therapies for inflammatory diseases refractory to conventional therapy, in particular those of the lung.

Protein chaperones: a composition of matter review (2008 - 2013)

INTRODUCTION

Heat shock proteins (Hsps) are proteins with important functions in regulating disease phenotypes. Historically, Hsp90 has first received recognition as a target in cancer, with consequent efforts extending its potential role to other diseases. Hsp70 has also attracted interest as a therapeutic target for its role as a co-chaperone to Hsp90 as well as its own anti-apoptotic roles.

AREAS COVERED

Herein, patents from 2008 to 2013 are reviewed to identify those that disclose composition of matter claimed to inhibit Hsp90 or Hsp70.

EXPERT OPINION

For Hsp90, there has been considerable creativity in the discovery of novel pharmacophores that fall outside the three initially discovered scaffolds (i.e., ansamycins, resorcinols and purines). Nonetheless, much of the patent literature appears to build on previously reported structure activity relationship through slight modifications of Hsp90 inhibitor space by finding weaknesses in existing patents. The major goal of future development of Hsp90 inhibitors is not necessarily identifying better molecules but rather understanding how to rationally use these agents in the clinic. The development of Hsp70 inhibitors has lagged behind. It will require a more concerted effort from the drug discovery community in order to begin to realize the potential of this target.

Hsp90 blockade modulates bullous pemphigoid IgG-induced IL-8 production by keratinocytes

Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering skin disease characterized by autoantibodies against the hemidesmosomal proteins BP180 and BP230. The cell stress chaperone heat shock protein 90 (Hsp90) has been implicated in inflammatory responses, and recent evidence suggests that it represents a novel treatment target in autoimmune bullous diseases. The aim of the study was to investigate the contribution of Hsp90 to the proinflammatory cytokine production in keratinocytes induced by autoantibodies to BP180 from BP patient serum. HaCaT cells were treated with purified human BP or normal IgG in the absence or presence of the Hsp90 blocker 17-DMAG and effects on viability, interleukin 6 (IL-6) and IL-8 (cytokines critical for BP pathology), NFκB (their major transcription factor), and Hsp70 (marker of effective Hsp90 inhibition and potent negative regulator of inflammatory responses) were investigated. We found that BP IgG stimulated IL-6 and IL-8 release from HaCaT cells and that non-toxic doses of 17-DMAG inhibited this IL-8, but not IL-6 secretion in a dose- and time-dependent fashion. Inhibition of this IL-8 production was also observed at the transcriptional level. In addition, 17-DMAG treatment blunted BP IgG-mediated upregulation of NFκB activity and was associated with Hsp70 induction. This study provides important insights that Hsp90 is involved as crucial regulator in anti-BP180 IgG-induced production of keratinocyte-derived IL-8. By adding to the knowledge of the multimodal anti-inflammatory effects of Hsp90 blockade, our data further support the introduction of Hsp90 inhibitors into the clinical setting for treatment of autoimmune diseases, especially for BP.

The role of toll-like receptor 4 in corneal epithelial wound healing

PURPOSE

We evaluated the role of Toll-like receptor 4 (TLR4) in corneal epithelial wound healing.

METHODS

The expression of TLR4 during in vivo corneal epithelial wound healing was examined by immunostaining in mice. The expression and activation of TLR4 was studied in primary or telomerase-immortalized human corneal epithelial cells (HCEC). Scratch assay was performed to evaluate in vitro wound closure using live time-lapse microscopy. Transwell migration assay and Ki67 immunostaining were done to evaluate migration and proliferation, respectively. Lipopolysaccharide (LPS) was used to activate TLR4, whereas CLI-095 was used for its inhibition. The expression of inflammatory cytokines was determined by RT-PCR and ELISA. The activation of p42/44 and p38 was determined by immunoblotting.

RESULTS

In the murine model, TLR4 immunostaining was noted prominently in the epithelium 8 hours after wounding. There was a 4-fold increase in the expression of TLR4 6 hours after in vitro scratch wounding (P < 0.001). Confocal microscopy confirmed the membrane localization of TLR4/MD2 complex. There was a significant increase in migration, proliferation, and wound closure in HCEC treated with LPS (P < 0.05), while there was significant decrease with TLR4 inhibition (P < 0.05). Addition of LPS to wounded HCEC resulted in a significant increase in the expression of IL-6, TNF-α, CXCL8/IL8, and CCL5/RANTES at the mRNA and protein levels. Likewise, LPS increased the activation of p42/44 and p38 in wounded HCEC.

CONCLUSIONS

These results suggest that epithelial wounding induces the expression of functional TLR4. Toll-like receptor 4 signaling appears to contribute to early corneal epithelial wound repair by enhancing migration and proliferation.

Novel mechanism of attenuation of LPS-induced NF-κB activation by the heat shock protein 90 inhibitor, 17-N-allylamino-17-demethoxygeldanamycin, in human lung microvascular endothelial cells

Heat shock protein (hsp) 90 inhibition attenuates NF-κB activation and blocks inflammation. However, the precise mechanism of NF-κB regulation by hsp90 in the endothelium is not clear. We investigated the mechanisms of hsp90 inhibition by 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) on NF-κB activation by LPS in primary human lung microvascular endothelial cells. Transcriptional activation of NF-κB was measured by luciferase reporter assay, gene expression by real-time RT-PCR, DNA binding of transcription factors by chromatin immunoprecipitation assay, protein-protein interaction by coimmunoprecipitation/immunoblotting, histone deacetylase (HDAC)/histone acetyltransferase enzyme activity by fluorometry, and nucleosome eviction by partial microccocal DNase digestion. In human lung microvascular endothelial cells, 17-AAG-induced degradation of IKBα was accomplished regardless of the phosphorylation/ubiquitination state of the protein. Hence, 17-AAG did not block LPS-induced NF-κB nuclear translocation and DNA binding activity. Instead, 17-AAG blocked the recruitment of the coactivator, cAMP response element binding protein binding protein, and prevented the assembly of a transcriptionally competent RNA polymerase II complex at the κB elements of the IKBα (an NF-κB-responsive gene) promoter. The effect of LPS on IKBα mRNA expression was associated with rapid deacetylation of histone-H3(Lys9) and a dramatic down-regulation of core histone H3 binding. Even though treatment with an HDAC inhibitor produced the same effect as hsp90 inhibition, the effect of 17-AAG was independent of HDAC. We conclude that hsp90 inhibition attenuates NF-κB transcriptional activation by preventing coactivator recruitment and nucleosome eviction from the target promoter in human lung endothelial cells.

Inhibitory effects of heat shock protein 90 blockade on proinflammatory human Th1 and Th17 cell subpopulations

Background

Heat shock protein 90 (Hsp90), a chaperone that regulates activity of many client proteins responsible for cellular growth, differentiation, and apoptosis, has been proposed as an important clinical and preclinical therapeutic target in a number of malignancies and autoimmune diseases, respectively. In this study, we evaluated the effects of pharmacological Hsp90 inhibition on human proinflammatory T cell responses.

Findings

Using anti-CD3 antibody-stimulated human peripheral blood mononuclear cell cultures, we observed that Hsp90 inhibition by non-toxic concentrations of the geldanamycin derivative 17-DMAG significantly blocked T cell proliferation, reduced IFN-γ and IL-17 expression on CD4⁺ T lymphocytes, and arrested secretion of proinflammatory IFN-γ, TNF-α, and IL-17, cytokines characteristic of Th1 and Th17 cells, respectively. These effects were associated with inhibition of NF-kB activity, upregulation of Hsp70 protein expression, and disruption of T cell-specific nonreceptor tyrosine kinase Lck activation.

Conclusions

Our results further support the potential use of Hsp90 inhibitors in patients with autoimmune diseases where uncontrolled Th1 or Th17 activation frequently occurs.

Sparse labeling of proteins: structural characterization from long range constraints

Structural characterization of biologically important proteins faces many challenges associated with degradation of resolution as molecular size increases and loss of resolution improving tools such as perdeuteration when non-bacterial hosts must be used for expression. In these cases, sparse isotopic labeling (single or small subsets of amino acids) combined with long range paramagnetic constraints and improved computational modeling offer an alternative. This perspective provides a brief overview of this approach and two discussions of potential applications; one involving a very large system (an Hsp90 homolog) in which perdeuteration is possible and methyl-TROSY sequences can potentially be used to improve resolution, and one involving ligand placement in a glycosylated protein where resolution is achieved by single amino acid labeling (the sialyltransferase, ST6Gal1). This is not intended as a comprehensive review, but as a discussion of future prospects that promise impact on important questions in the structural biology area.

Inhibition of N-terminal ATPase on HSP90 attenuates colitis through enhanced Treg function

Inflammatory bowel disease (IBD) is a chronic inflammatory condition thought to reflect a failure of the enteral immune system to adequately regulate itself. Inflammatory stress drives upregulation of heat-shock proteins (HSPs), including the pro-inflammatory chaperone, HSP90. This protein sequesters the transcription factor, heat-shock factor 1 (HSF1) in the cytoplasm preventing transcription of a number of anti-inflammatory proteins. We hypothesized that inhibition of HSP90 would exert an anti-inflammatory effect and thereby attenuate intestinal inflammation in murine models of IBD. Inhibition of HSP90 with 17-allylaminogeldanamycin (17-AAG) reduced inflammation in acute dextran sodium sulfate and chronic CD45RB(High) colitis models coinciding with increased interleukin (IL)-10 production in the colon. Regulatory T cells (Tregs) from mice treated with 17-AAG demonstrated significantly greater suppressive capacity in vitro abolished in HSF1-/- or IL-10-/- cells. Finally, Tregs treated with 17-AAG exhibited increased nuclear localization of HSF1 with resultant upregulation of HSF1 response genes, including HSP70, HSP90 and IL-10.

Experimental and structural testing module to analyze paralogue-specificity and affinity in the Hsp90 inhibitors series

We here describe the first reported comprehensive analysis of Hsp90 paralogue affinity and selectivity in the clinical Hsp90 inhibitor chemotypes. This has been possible through the development of a versatile experimental assay based on a new FP-probe (16a) that we both describe here. The assay can test rapidly and accurately the binding affinity of all major Hsp90 chemotypes and has a testing range that spans low nanomolar to millimolar binding affinities. We couple this assay with a computational analysis that allows for rationalization of paralogue selectivity and defines not only the major binding modes that relay pan-paralogue binding or, conversely, paralogue selectivity, but also identifies molecular characteristics that impart such features. The methods developed here provide a blueprint for parsing out the contribution of the four Hsp90 paralogues to the perceived biological activity with the current Hsp90 chemotypes and set the ground for the development of paralogue selective inhibitors.

Aberrant expression and secretion of heat shock protein 90 in patients with bullous pemphigoid

The cell stress chaperone heat shock protein 90 (Hsp90) has been implicated in inflammatory responses and its inhibition has proven successful in different mouse models of autoimmune diseases, including epidermolysis bullosa acquisita. Here, we investigated expression levels and secretory responses of Hsp90 in patients with bullous pemphigoid (BP), the most common subepidermal autoimmune blistering skin disease. In comparison to healthy controls, the following observations were made: (i) Hsp90 was highly expressed in the skin of BP patients, whereas its serum levels were decreased and inversely associated with IgG autoantibody levels against the NC16A immunodominant region of the BP180 autoantigen, (ii) in contrast, neither aberrant levels of circulating Hsp90 nor any correlation of this protein with serum autoantibodies was found in a control cohort of autoimmune bullous disease patients with pemphigus vulgaris, (iii) Hsp90 was highly expressed in and restrictedly released from peripheral blood mononuclear cells of BP patients, and (iv) Hsp90 was potently induced in and restrictedly secreted from human keratinocyte (HaCaT) cells by BP serum and isolated anti-BP180 NC16A IgG autoantibodies, respectively. Our results reveal an upregulated Hsp90 expression at the site of inflammation and an autoantibody-mediated dysregulation of the intracellular and extracellular distribution of this chaperone in BP patients. These findings suggest that Hsp90 may play a pathophysiological role and represent a novel potential treatment target in BP.

Tumor-intrinsic and tumor-extrinsic factors impacting hsp90- targeted therapy

In 1994 the first heat shock protein 90 (Hsp90) inhibitor was identified and Hsp90 was reported to be a target for anticancer therapeutics. In the past 18 years there have been 17 distinct Hsp90 inhibitors entered into clinical trial, and the small molecule Hsp90 inhibitors have been highly valuable as probes of the role of Hsp90 and its client proteins in cancer. Although no Hsp90 inhibitor has achieved regulatory approval, recently there has been significant progress in Hsp90 inhibitor clinical development, and in the past year RECIST responses have been documented in HER2-positive breast cancer and EML4-ALK-positive non-small cell lung cancer. All of the clinical Hsp90 inhibitors studied to date are specific in their target, i.e. they bind exclusively to Hsp90 and two related heat shock proteins. However, Hsp90 inhibitors are markedly pleiotropic, causing degradation of over 200 client proteins and impacting critical multiprotein complexes. Furthermore, it has only recently been appreciated that Hsp90 inhibitors can, paradoxically, cause transient activation of the protein kinase clients they are chaperoning, resulting in initiation of signal transduction and significant physiological events in both tumor and tumor microenvironment. An additional area of recent progress in Hsp90 research is in studies of the posttranslational modifications of Hsp90 itself and Hsp90 co-chaperone proteins. Together, a picture is emerging in which the impact of Hsp90 inhibitors is shaped by the tumor intracellular and extracellular milieu, and in which Hsp90 inhibitors impact tumor and host on a microenvironmental and systems level. Here we review the tumor intrinsic and extrinsic factors that impact the efficacy of small molecules engaging the Hsp90 chaperone machine.

Gut microbiota imbalance and chaperoning system malfunction are central to ulcerative colitis pathogenesis and can be counteracted with specifically designed probiotics: a working hypothesis

In this work, we propose that for further studies of the physiopathology and treatment for inflammatory bowel diseases, an integral view of the conditions, including the triad of microbiota-heat shock proteins (HSPs)-probiotics, ought to be considered. Microbiota is the complex microbial flora that resides in the gut, affecting not only gut functions but also the health status of the whole body. Alteration in the microbiota's composition has been implicated in a variety of pathological conditions (e.g., ulcerative colitis, UC), involving both gut and extra-intestinal tissues and organs. Some of these pathologies are also associated with an altered expression of HSPs (chaperones) and this is the reason why they may be considered chaperonopathies. Probiotics, which are live microorganisms able to restore the correct, healthy equilibrium of microbiota composition, can ameliorate symptoms in patients suffering from UC and modulate expression levels of HSPs. However, currently probiotic therapy follows ex-adiuvantibus criteria, i.e., treatments with beneficial effects but whose mechanism of action is unknown, which should be changed so the probiotics needed in each case are predetermined on the basis of the patient's microbiota. Consequently, efforts are necessary to develop diagnostic tools for elucidating levels and distribution of HSPs and the microbiota composition (microbiota fingerprint) of each subject and, thus, guide specific probiotic therapy, tailored to meet the needs of the patient. Microbiota fingerprinting ought to include molecular biology techniques for sequencing highly conserved DNA, e.g., genes encoding 16S RNA, for species identification and, in addition, quantification of each relevant microbe.