Pharmacological Study of 2-hydroxypropyl-β-cyclodextrin

Introduction

2-Hydroxypropyl-β-cyclodextrin (HP-BCD; Figure 1), a hydroxyalkyl derivative of β-cyclodextrin, with improved water solubility properties and may be slightly more toxicologically benign, was considered a potential alternative of β-cyclodextrin. 2-Hydroxypropyl-β-cyclodextrin have widely applications in food, agriculture and pharmaceutical field. [1] 

1. 2‑Hydroxypropyl‑β‑cyclodextrin blocks autophagy flux andtriggers caspase‑8‑mediated apoptotic cascades in HepG2 cells

2-Hydroxypropyl-β-cyclodextrin, a chemically-modified water-soluble cyclodextrin derivative, has been widely utilized as a drug delivery system, as well as an efficient therapeutic strategy for neurodegenerative diseases and atherosclerosis regression, due to its distinctive capability of regulating cellular cholesterol transport and metabolism. Moreover, the main target organs of HP-BCD are the kidney, liver, lungs and spleen. Approved by the Food and Drug Administration (FDA), HP-BCD is recognized as a relatively innocuous therapeutic, butits adverse effects have rarely been investigated. However, it has been reported that a high dose 2-hydroxypropyl-β-cyclodextrin could impede autophagy flux in fibroblasts and in a mouse model of Alzheimer's disease (AD). Furthermore, 2-hydroxypropyl-β-cyclodextrin serves as a potent molecule for inducing apoptosis in human leukemiccell lines. Collectively, these findings suggest potential negative effects of long-term administration of 2-hydroxypropyl-β-cyclodextrin. Therefore, the present study examined the dose-response effects of 2-hydroxypropyl-β-cyclodextrin on autophagy and apoptosis in a liver cancer cell line (HepG2), which is widely used as a cellular model for normal hepatocytes to assess the potential of chemical hepatotoxicity.[2]

It was found that a high dose (20 mM) of 2-hydroxypropyl-β-cyclodextrin treatment significantly inhibited the AKT/mTOR pathway and disrupted infusion of autophagosomes and lysosomes, which rapidly led to massive autophagosome accumulation in HepG2 cells. The autophagosomal membrane serves as a platform for caspase-8 oligomerization, which is considered as the key step for its self‑activation. Using flow cytometry and T assay, increased apoptosis of HepG2cells treated with a high dose HP-BCD (20 mM) for 48 h was observed. In addition, western blotting results demonstrated that the expression of cleaved-caspase-8 was positively associated with microtubule-associated protein 1 light chain 3 BⅡexpression, which is an indicator of autophagosome level in the cytoplasm. Therefore, the present study provided novel evidence that HP-BCD might be a potential risk contributing to the pathophysiological process of hepatic diseases, especially in an autophagy-deficient state.[2]

2. Pro-Inflammatory Implications of 2-Hydroxypropyl-β-cyclodextrin Treatment

In this context, 2-hydroxypropyl-β-cyclodextrin is increasingly considered as a novel pharmacological compound to decrease cellular cholesterol levels due to its ability to increase cholesterol solubility. However, recent findings have reported contra-indicating events after the use of 2-hydroxypropyl-β-cyclodextrin questioning the clinical applicability of this compound. Given its potential as a therapeutic compound in metabolic inflammatory diseases, in this study, we evaluated the inflammatory effects of 2-hydroxypropyl-β-cyclodextrin administration in the context of cholesterol induced metabolic inflammation in vivo and in vitro. The inflammatory and cholesterol depleting effects of 2-hydroxypropyl-β-cyclodextrin were first investigated in low-density lipoprotein receptor knockout (Ldlr-/) mice that were transplanted with Npc1nih or Npc1wt bone marrow and were fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 12 weeks, thereby creating an extreme model of lysosomal cholesterol-induced metabolic inflammation. In the final three weeks, these mice received daily injections of either control (saline) or 2-hydroxypropyl-β-cyclodextrin subcutaneously. Subsequently, the inflammatory properties of 2-hydroxypropyl-β-cyclodextrin were investigated in vitro in two macrophage cell lines and in murine bone marrow-derived macrophages (BMDMs). While HP-BCD administration improved cholesterol mobilization outside lysosomes in BMDMs, an overall pro-inflammatory profile was observed after 2-hydroxypropyl-β-cyclodextrin treatment, evidenced by increased hepatic inflammation in vivo and a strong increase in cytokine release and inflammatory gene expression in vitro in murine BMDMs and macrophages cell lines. Nevertheless, this 2-hydroxypropyl-β-cyclodextrin-induced pro-inflammatory profile was time-dependent, as short term exposure to CD did not result in a pro-inflammatory response in BMDM. While 2-hydroxypropyl-β-cyclodextrin exerts desired cholesterol-depleting effects, its inflammatory effect is dependent on the exposure time. As such, using 2-hydroxypropyl-β-cyclodextrin in the clinic, especially in a metabolic inflammatory context, should be closely monitored as it may lead to undesired, pro-inflammatory side effects.[3]

3. 2-Hydroxypropyl-β-Cyclodextrin Treatment Induces Modest Immune Activation in Healthy Rhesus Macaques

2-Hydroxypropyl-β-Cyclodextrin is a chemically modified, cyclic oligosaccharide long considered a pharmaceutical excipient and has been used to solubilize and stabilize many compounds for parenteral use in vivo. However, 2-hydroxypropyl-β-cyclodextrin also solubilizes lipids, including cellular cholesterol. Indeed, the administration of 2-hydroxypropyl-β-cyclodextrin alone has been shown to provide a significant therapeutic benefit in patients with Niemann-Pick disease type C, a lysosomal cholesterol storage disorder . It is unclear how the lipid mobilization properties of 2-hydroxypropyl-β-cyclodextrin might influence inflammation in vivo. Whereas HIV impairs cholesterol efflux in macrophages, 2-hydroxypropyl-β-cyclodextrin administration improves macrophage cholesterol efflux. On the other hand, the ability of 2-hydroxypropyl-β-cyclodextrin treatment to destabilize cell surface CCR5 integrity may impair or mask the recovery of target CD41 T cells in treated macaques in vivo.[4]

Alexandra M. Ortiz et al. hypothesized that the coformulation solubilizing agent Kleptose (2-hydroxypropyl-β-cyclodextrin [HP-BCD]) may induce inflammation with myeloid cell activation and the release of sCD14. Herein, they stimulated peripheral blood mononuclear cells (PBMCs) from healthy macaques with HP-BCD from different commercial sources and evaluated inflammatory cytokine production in vitro. Treatment of PBMCs resulted in increased sCD14 release and myeloid cell interleukin-1b (IL-1b) production—with stimulation varying significantly by 2-hydroxypropyl-β-cyclodextrin source—and destabilized lymphocyte CCR5 surface expression.  In vivo, they observed modestly increased myeloid cell activation in response to Kleptose treatment without significant perturbation of the immunological transcriptome or epigenome. The results demonstrate a need for vehicle-only controls and highlight immunological perturbations that can occur when using 2-hydroxypropyl-β-cyclodextrin in pharmaceutical coformulations.[4]

References

[1] Bezerra BB, Silva GPDD, Coelho SVA, et al. Hydroxypropyl-beta-cyclodextrin (HP-BCD) inhibits SARS-CoV-2 replication and virus-induced inflammatory cytokines. Antiviral Res. 2022;205:105373. doi:10.1016/j.antiviral.2022.105373

[2] Sun H, Zong H, Wu G. 2‑Hydroxypropyl‑β‑cyclodextrin blocks autophagy flux and triggers caspase‑8‑mediated apoptotic cascades in HepG2 cells. Mol Med Rep. 2020;22(3):1901-1909. doi:10.3892/mmr.2020.11282

[3] Houben T, Yadati T, de Kruijf R, et al. Pro-Inflammatory Implications of 2-Hydroxypropyl-β-cyclodextrin Treatment. Front Immunol. 2021;12:716357. Published 2021 Aug 20. doi:10.3389/fimmu.2021.716357

[4] Ortiz AM, Castello Casta F, Rahmberg A, et al. 2-Hydroxypropyl-β-Cyclodextrin Treatment Induces Modest Immune Activation in Healthy Rhesus Macaques. J Virol. 2023;97(7):e0060023. doi:10.1128/jvi.00600-23

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