Exploring the Effects of Cyclosporin A to Isocyclosporin A Rearrangement on Ion Mobility Separation.

Cyclosporin A (CycA) is a peptide secondary metabolite derived from fungi that plays a crucial role in transplantation surgery. Cyclic traveling wave ion mobility mass spectrometry (IM-MS) revealed an N → O peptidyl shift in singly protonated CycA to isocyclosporin A (isoA), whereas no such isomerization was observed for doubly protonated and sodiated molecules. CycA and isoA were able to be separated by considering doubly protonated precursors using a specific ion fragment. In parallel, sodium ion stabilization facilitated the simultaneous separation and quantitation of singly charged cyclosporin isomers with the limit of detection and coefficient of determination of 1.3% and 0.9908 for CycA in isoA and 1.0% and 0.9830 for isoA in CycA, respectively. Finally, 1H-13C gHSQC NMR experiments permitted parallel recording of up to 11 cyclosporin conformers. The ratios were determined by integrating the volume of cross-peaks of the upfield resonating hydrogen in the diastereotopic methylene group of sarcosine-3.

Expression and biochemical characterization of the putative insulinase enzyme PF11_0189 found in the Plasmodium falciparum genome.

PF11_0189 is a putative insulin degrading enzyme present in Plasmodium falciparum genome. The catalytic domain of PF11_0189 is about 27 kDa. Substrate specificity study shows PF11_0189 acts upon different types of proteins. The substrate specificity is found to be highest when insulin is used as a substrate. Metal dependency study shows highest dependency of PF11_0189 towards zinc metal for its proteolytic activity. Chelation of zinc metal with EDTA shows complete absence of PF11_0189 activity. Peptide inhibitors, P-70 and P-121 from combinatorial peptide library prepared against PF11_0189 show inhibition with an IC50 value of 4.8 µM and 7.5 µM respectively. A proven natural anti-malarial peptide cyclosporin A shows complete inhibition against PF11_0189 with an IC50 value of 0.75 µM suggesting PF11_0189 as a potential target for peptide inhibitors. The study implicates that PF11_0189 is a zinc metalloprotease involved in catalysis of insulin. The study gives a preliminary insight into the mechanism of complications arising from glucose abnormalities during severe malaria.

Drug-Modified Contact Lenses-Properties, Release Kinetics, and Stability of Active Substances with Particular Emphasis on Cyclosporine A: A Review.

The following review focuses on the manufacturing and parameterizing of ocular drug delivery systems (DDS) using polymeric materials to create soft contact lenses. It discusses the types of drugs embedded into contact lenses, the various polymeric materials used in their production, methods for assessing the mechanical properties of polymers, and techniques for studying drug release kinetics. The article also explores strategies for investigating the stability of active substances released from contact lenses. It specifically emphasizes the production of soft contact lenses modified with Cyclosporine A (CyA) for the topical treatment of specific ocular conditions. The review pays attention to methods for monitoring the stability of Cyclosporine A within the discussed DDS, as well as investigating the influence of polymer matrix type on the stability and release of CyA.

Silk Fibroin Formed Bioadhesive Ophthalmic Gel for Dry Eye Syndrome Treatment.

PURPOSE: Dry eye syndrome (DES), arising from various etiologic factors, leads to tear film instability and ocular surface damage. Given its anti-inflammatory effects, cyclosporine A (CsA) has been widely used as a short-term treatment option for DES. However, poor bioavailability and solubility of CsA in aqueous phase make the development of a cyclosporine A-based eye drop for ocular topical application a huge challenge. METHODS: In this study, a novel strategy for preparing cyclosporine A-loaded silk fibroin nanoemulsion gel (CsA NBGs) was proposed to address these barriers. Additionally, the rheological properties, ocular irritation potential, tear elimination kinetics, and pharmacodynamics based on a rabbit dry eye model were investigated for the prepared CsA NBGs. Furthermore, the transcorneal mechanism across the ocular barrier was also investigated. RESULTS: The pharmacodynamics and pharmacokinetics of CsA NBGs exhibited superior performance compared to cyclosporine eye drops, leading to a significant enhancement in the bioavailability of CsA NBGs. Furthermore, our investigation into the transcorneal mechanism of CsA NBGs revealed their ability to be absorbed by corneal epithelial cells via the paracellular pathway. CONCLUSION: The CsA NBG formulation exhibits promising potential for intraocular drug delivery, enabling safe, effective, and controlled administration of hydrophobic drugs into the eye. Moreover, it enhances drug retention within the ocular tissues and improves systemic bioavailability, thereby demonstrating significant clinical translational prospects.

Targeting Cyclophilin A and CD147 to Inhibit Replication of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and SARS-CoV-2-Induced Inflammation.

Identification and development of effective therapeutics for coronavirus disease 2019 (COVID-19) are still urgently needed. The CD147-spike interaction is involved in the severe acute respiratory syndrome coronavirus (SARS-CoV)-2 invasion process in addition to angiotensin-converting enzyme 2 (ACE2). Cyclophilin A (CyPA), the extracellular ligand of CD147, has been found to play a role in the infection and replication of coronaviruses. In this study, our results show that CyPA inhibitors such as cyclosporine A (CsA) and STG-175 can suppress the intracellular replication of SARS-CoV-2 by inhibiting the binding of CyPA to the SARS-CoV-2 nucleocapsid C-terminal domain (N-CTD), and the IC50 is 0.23 µM and 0.17 µM, respectively. Due to high homology, CsA also had inhibitory effects on SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), and the IC50 is 3.2 µM and 2.8 µM, respectively. Finally, we generated a formulation of phosphatidylserine (PS)-liposome-CsA for pulmonary drug delivery. These findings provide a scientific basis for identifying CyPA as a potential drug target for the treatment of COVID-19 as well as for the development of broad-spectrum inhibitors for coronavirus via targeting CyPA. Highlights: 1) SARS-CoV-2 infects cells via the binding of its S protein and CD147; 2) binding of SARS-CoV-2 N protein and CyPA is essential for viral replication; 3) CD147 and CyPA are potential therapeutic targets for SARS-CoV-2; and 4) CsA is a potential therapeutic strategy by interrupting CD147/CyPA interactions. SIGNIFICANCE STATEMENT: New severe acute respiratory syndrome coronavirus (SARS-CoV)-2 variants and other pathogenic coronaviruses (CoVs) are continually emerging, and new broad-spectrum anti-CoV therapy is urgently needed. We found that binding sites of cyclophilin A/cyclosporin A (CyPA/CsA) overlap with CyPA/N-CTD (nucleocapsid C-terminal domain), which shows the potential to target CyPA during SARS-CoV-2 infection. Here, we provide new evidence for targeting CyPA in the treatment of coronavirus disease 2019 (COVID-19) as well as the potential of developing CyPA inhibitors for broad-spectrum inhibition of CoVs.

Transition from Amorphous Cyclosporin A Nanoparticles to Size-Reduced Stable Nanocrystals in a Poloxamer 407 Solution.

Amorphous drug nanoparticles usually exhibit low storage stability. A comprehensive understanding of the molecular states and physicochemical properties of the product is indispensable for designing stable formulations. In the present study, an amorphous cyclosporin A (CyA) nanosuspension with a mean particle size of approximately 370 nm was prepared by wet bead milling with poloxamer 407 (P407). Interestingly, the prepared amorphous CyA nanoparticles were transformed into uniform CyA nanocrystals with a reduced mean particle size of approximately 200 nm during storage at 25 °C. The CyA nanocrystals were stably maintained for at least 1 month. The particle morphologies and molecular structures of the CyA nanosuspensions before and after storage were thoroughly characterized by cryogenic transmission electron microscopy and magic-angle spinning nuclear magnetic resonance spectroscopy, respectively. They revealed that the freshly prepared amorphous CyA nanoparticles (∼370 nm) were secondary particles composed of aggregated primary particles with an estimated size of 50 nm. A portion of P407 was found to be entrapped at the gaps between the primary particles due to aggregation, while most of P407 was dissolved in the solution either adsorbing at the solid/liquid interface or forming polymeric micelles. The entrapped P407 is considered to play an important role in the destabilization of the amorphous CyA nanoparticles. The resultant CyA nanocrystals (∼200 nm) were uniform single crystals of Form 2 hydrate and showed corner-truncated bipyramidal features. Owing to the narrow particle size distribution of the CyA nanocrystals, the rate of Ostwald ripening was slow, giving long-term stability to the CyA nanocrystals. This study provides new insights into the destabilization mechanism of amorphous drug nanoparticles.

Non-Immunosuppressive Cyclophilin Inhibitors.

Cyclophilins, enzymes with peptidyl-prolyl cis/trans isomerase activity, are relevant to a large variety of biological processes. The most abundant member of this enzyme family, cyclophilin A, is the cellular receptor of the immunosuppressive drug cyclosporine A (CsA). As a consequence of the pathophysiological role of cyclophilins, particularly in viral infections, there is a broad interest in cyclophilin inhibition devoid of immunosuppressive activity. This Review first gives an introduction into the physiological and pathophysiological roles of cyclophilins. The presentation of non-immunosuppressive cyclophilin inhibitors will commence with drugs based on chemical modifications of CsA. The naturally occurring macrocyclic sanglifehrins have become other lead structures for cyclophilin-inhibiting drugs. Finally, de novo designed compounds, whose structures are not derived from or inspired by natural products, will be presented. Relevant synthetic concepts will be discussed, but the focus will also be on biochemical studies, structure-activity relationships, and clinical studies.

Cyclosporine A Nanosuspensions for Ophthalmic Delivery: A Comparative Study between Cationic Nanoparticles and Drug-Core Mucus Penetrating Nanoparticles.

The effect of mucin on ocular bioavailability depends on the extent to which it acts as a barrier or retention site. Mucus penetrating particles (MPPs) can evade the mucus entrapment and associated rapid clearance, but cationic nanoparticles have high adhesion to the mucosa. Both formulations can prolong the drug residence time on the surface of the eyes. The purpose of this work is to compare the effects of mucoadhesion of cationic nanoparticles and mucous permeability of MPPs on ocular bioavailability. Cationic nanosuspensions and drug-core MPP nanosuspensions were developed using the anti-solvent precipitation method. The results of X-ray diffraction revealed that CsA was amorphous. In vitro mucoadhesion evaluation demonstrated that cationic nanosuspensions enhanced the interaction with pig mucin about 5.0-6.0 fold compared to drug-core MPP nanosuspensions. A mucus permeation study by the transwell diffusion system showed that the Papp values of drug-core MPP nanosuspensions were 5.0-10.0 times higher than those of cationic nanosuspensions. In vivo ocular bioavailability evaluation of those CsA formulations was conducted in rabbits using a conventional nanosuspension as a comparison. The CsA concentrations in the cornea following the administration of a cationic nanosuspension and a drug-core MPP nanosuspension were 13,641.10 ng/g and 11,436.07 ng/g, respectively, significantly higher than that of the conventional nanosuspension (8310.762 ng/g). The results showed that both the cationic and MPP nanosuspensions were able to deliver CsA to anterior ocular tissues in effective therapeutic concentrations (10-20 µg/g) with topical drop instillation. The cationic nanosuspension could achieve relatively higher bioavailability than the MPP nanosuspension. The cationic nanosuspension would be a promising ocular drug delivery system.

Molecular Dynamics Simulations and Experimental Results Provide Insight into Clinical Performance Differences between Sandimmune® and Neoral® Lipid-Based Formulations.

OBJECTIVE: Molecular dynamics (MD) simulations provide an in silico method to study the structure of lipid-based formulations (LBFs) and the incorporation of poorly water-soluble drugs within such formulations. In order to validate the ability of MD to effectively model the properties of LBFs, this work investigates the well-known cyclosporine A formulations, Sandimmune® and Neoral®. Sandimmune® exhibits poor dispersibility and its absorption from the gastrointestinal tract is enhanced when administered after food, whereas Neoral® disperses comparatively well and shows no food effect. METHODS: MD simulations were performed of both LBFs to investigate the differences observed in fasted and fed conditions. These conditions were also tested using an in vitro experimental model of dispersion and digestion. RESULTS: These MD simulations were able to show that the food effect observed for Sandimmune® can be explained by large changes in drug solubilization on addition of bile. In contrast, Neoral® is well dispersed in water or in simulated fasted conditions, and this dispersion is relatively unchanged on moving to fed conditions. These differences were confirmed using dispersion and digestion in vitro experimental model. CONCLUSIONS: The current data suggests that MD simulations are a potential method to model the fate of LBFs in the gastrointestinal tract, predict their dispersion and digestion, investigate behaviour of APIs within the formulations, and provide insights into the clinical performance of LBFs.

Application of Design of Experiments® Approach-Driven Artificial Intelligence and Machine Learning for Systematic Optimization of Reverse Phase High Performance Liquid Chromatography Method to Analyze Simultaneously Two Drugs (Cyclosporin A and Etodolac) in Solution, Human Plasma, Nanocapsules, and Emulsions.

The objectives of current investigation are (1) to find out wavelength of maximum absorbance (λmax) for combined cyclosporin A and etodolac solution followed by selection of mobile phase suitable for the RP-HPLC method, (2) to define analytical target profile and critical analytical attributes (CAAs) for the analytical quality by design, (3) to screen critical method parameters with the help of full factorial design followed by optimization with face-centered central composite design (CCD) approach-driven artificial neural network (ANN)-linked with the Levenberg-Marquardt (LM) algorithm for finding the RP-HPLC conditions, (4) to perform validation of analytical procedures (trueness, linearity, precision, robustness, specificity and sensitivity) using combined drug solution, and (5) to determine drug entrapment efficiency value in dual drug-loaded nanocapsules/emulsions, percentage recovery value in human plasma spiked with two drugs and solution state stability analysis at different stress conditions for substantiating the double-stage systematically optimized RP-HPLC method conditions. Through isobestic point and scouting step, 205 nm and ACN:H2O mixture (74:26) were selected respectively as the λmax and mobile phase. The ANN topology (3:10:4) indicating the input, hidden and output layers were generated by taking the 20 trials produced from the face-centered CCD model. The ANN-linked LM model produced minimal differences between predicted and observed values of output parameters (or CAAs), low mean squared error and higher correlation coefficient values in comparison to the respective values produced by face-centered CCD model. The optimized RP-HPLC method could be applied to analyze two drugs concurrently in different formulations, human plasma and solution state stability checking.

Comparison of cyclosporin variants B-E based on their structural properties and activity in mitochondrial membranes.

Cyclosporins B, C, D, and E were characterized by NMR spectroscopy, and backbone flexibility was studied by molecular dynamics simulation. Structures of the molecules were characterized by nuclear Overhauser effect spectroscopy, which revealed that the studied peptides have many common features. Molecular dynamics simulation showed that the backbone of cyclosporin E is relatively more rigid than in other peptides. Calcium-dependent swelling of liver mitochondria under the influence of four considered compounds was also investigated. Three of them were found to have the activity similar to cyclosporin A, inhibiting opening of the mitochondrial pore at concentrations within 100-300 nM. However, cyclosporin E did not show any biological effect at concentrations up to 1 µM. Results of this study agree with the idea on the correlation between the peptide chain flexibility and its bioavailability.

Discovery of a novel 9-position modified second-generation anti-HCV candidate via bioconversion and semi-synthesis of FR901459.

Evidence that hepatitis C virus (HCV) utilizes cellular cyclophilin proteins in the virus replication cycle has increased attention on cyclophilin inhibitors as attractive therapeutic targets in the treatment of HCV. Previous reports have described a number of non-immunosuppressive cyclophilin inhibitors, most of which require many synthetic steps for their preparation. Sasamura et al. have previously reported the isolation of bioconversion derivative 4. This analog is a convenient starting point for optimization due to the presence of the readily modifiable primary hydroxyl group and because it shows moderate anti-HCV activity and decreased immunosuppressive activity. We have also established an efficient C-alkylation reaction at the 3-position. Through a detailed structure-activity relationship study, we discovered a new type of clinical candidate 14 which requires a short synthetic process and has potent anti-HCV activity and reduced immunosuppressive activity, as well as improved aqueous solubility and pharmacokinetics.

Development of an efficient semisynthetic modification of FR901459 via a novel regioselective N, O-acyl migration.

HCV utilizes cellular protein cyclophilins in the virus replication cycle and cyclophilin inhibitors have become a new class of anti-HCV agents. In our screening of natural products, we identified a unique cyclosporin analogue, FR901459, as a cyclophilin inhibitor with potent anti-HCV activity. In this work, we developed an efficient synthetic methodology to prepare FR901459 derivatives via an N, O-acyl migration reaction. This method allows us to efficiently manipulate the amino acid residues at the 3 position while avoiding lengthy total synthesis for each compound. By using this methodology, we discovered 4, which has superior anti-HCV activity and decreased immunosuppressive activity compared to FR901459.

Immunosuppressants in Organ Transplantation.

The goal of immunosuppressive therapy post-transplantation in pediatric renal transplant recipients is to prevent acute and chronic rejection while minimizing drug side effects. Most therapies alter immune response mechanisms but are not immunologically specific, and a careful balance is required to find the dose that prevents rejection of the graft while minimizing the risks of overimmunosuppression leading to infection and cancer. While this chapter because of space constraints focuses on immunosuppressive therapy in pediatric renal transplant recipients, many aspects can be applied on pediatric recipients of other solid organ transplants such as the liver and heart. The major maintenance immunosuppressive agents currently used in various combination regimens are tacrolimus, cyclosporine, mycophenolate mofetil, azathioprine, everolimus, sirolimus, and glucocorticoids (steroids). Although data from adult renal transplantation trials are used to help guide management decisions in pediatric patients, immunosuppressive therapy in pediatric renal transplant recipients often must be modified because of the unique dosage requirements and clinical effects of these agents in children, including their impact on growth and development. The optimal immunosuppressive therapy post-transplant is not established. The goal remains to find the best combination of immunosuppressive agents that optimizes allograft survival by preventing acute rejection while limiting drug toxicities.

Topical nano-encapsulated cyclosporine formulation for atopic dermatitis treatment.

Systemic cyclosporine A (CsA) therapy shows efficacy in the treatment of recalcitrant severe atopic dermatitis (AD) but elicits severe side-effects. Thus, a topical formulation of CsA nanocapsules (NCs), able to potentially bypass these drawbacks, was developed. CsA-NCs were shown to enhance drug penetration into the various layers of porcine ear skin. Furthermore, the encapsulated CsA was biologically active, as shown in vitro on mouse splenocytes, reflected by inhibition of both cell proliferation and of interleukin (IL)-2 secretion. Ex-vivo efficacy was demonstrated on human skin organ culture by markedly reducing pro-inflammatory cytokines secretion. Finally, CsA-NCs topical formulation elicited improved efficacy in terms of better preservation of the skin barrier integrity, a decrease of the systemic pro-inflammation markers and reduced skin inflammation. The overall results suggest that this original topical platform may provide a novel therapeutic tool of clinical significance compared to the existing topical therapeutic drugs in AD.

Preparation, characterization, and in vivo evaluation of cyclosporine cationic liposomes for the treatment of psoriasis.

Cyclosporine (CYC), a calcineurin inhibitor acts specifically on T-cells and is one of the most effective treatment options for psoriasis. Systemic administration of the drug has been associated with dose-dependent toxic effects, while its topical delivery is a challenging task due to unfavourable physicochemical properties of drug. The aim of the present study is to develop and evaluate the efficacy of topical liposomal gel containing CYC loaded cationic liposomal nanocarriers in imiquimod induced psoriatic plaque model. Liposomes composed of DOTAP and cholesterol was formulated by different liposomal preparation techniques. Optimized liposomal carriers prepared by ethanol injection method were characterized with respect to size, zeta potential, entrapment efficiency, stability, in vitro drug release and in vivo studies. Cationic liposomes with particle size of 111 ± 1.62 nm, PDI of 0.27 ± 0.08, entrapment efficiency of 93 ± 2.12%, and zeta potential of 41.12 ± 3.56 mV were obtained. Drug loaded liposomal gels showed shear thinning behaviour, which is suitable for topical application. Topical application of CYC liposomal gels on imiquimod induced psoriatic plaque model reduced the symptoms of psoriasis and levels of key psoriatic cytokines such as tumour necrosis factor-α, IL-17, and IL-22. In conclusion, the developed liposomal carrier of CYC was found to be effective and can find application in treatment of psoriasis.

Viscosified Solid Lipidic Nanoparticles Based on Naringenin and Linolenic Acid for the Release of Cyclosporine A on the Skin.

Psoriasis is one of the most common human skin disorders. Although its pathogenesis is complex and not completely know, the hyperactivation of the immune system seem to have a key role. In this regard, among the most effective systemic therapeutics used in psoriasis, we find cyclosporine, an immunosuppressive medication. However, one of the major problems associated with the use of cyclosporine is the occurrence of systemic side effects such as nephrotoxicity, hypertension, etc. The present work fits in this context and its aim is the design of suitable platforms for cyclosporine topical release in psoriasis treatment. The main objective is to achieve local administration of cyclosporine in order to reduce its systemic absorption and, consequently, its side effects. In order to improve dermal penetration, solid lipid nanoparticles (SLNs) are used as carriers, due to their lipophilicity and occlusive properties, and naringenin and linolenic acid are chosen, due to their properties, as starting materials for SLNs design. In order to have dermatological formulations and further modulate drug release, SLNs are incorporated in several topical vehicles obtaining gels with different degree of lipophilicity. Potential applications for psoriasis treatment were evaluated by considering the encapsulation efficiency, release profiles, in vitro skin permeation, and anti-inflammatory effects.

Synthesis and Characterization of Bodipy-FL-Cyclosporine A as a Substrate for Multidrug Resistance-Linked P-Glycoprotein (ABCB1).

Fluorescent conjugates of drugs can be used to study cellular functions and pharmacology. These compounds interact with proteins as substrates or inhibitors, helping in the development of unique fluorescence-based methods to study in vivo localization and molecular mechanisms. P-glycoprotein (P-gp, ABCB1) is an ATP-binding cassette (ABC) transporter that effluxes most anticancer drugs from cells, contributing to the development of drug resistance. To study the transport function of P-gp, we synthesized a Bodipy-labeled fluorescent conjugate of cyclosporine A (BD-CsA). After synthesis and characterization of its chemical purity, BD-CsA was compared with the commonly used 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-CsA probe. In flow cytometry assays, the fluorescence intensity of BD-CsA was almost 10 times greater than that of NBD-CsA, enabling us to use significantly lower concentrations of BD-CsA to achieve the same fluorescence levels. We found that BD-CsA is recognized as a transport substrate by both human and mouse P-gp. The rate of efflux of BD-CsA by human P-gp is comparable to that of NBD-CsA. The transport of BD-CsA was inhibited by tariquidar, with similar IC50 values to those for NBD-CsA. BD-CsA and NBD-CsA both partially inhibited the ATPase activity of P-gp with similar IC50 values. In silico docking of BD-CsA and NBD-CsA to the human P-gp structure indicates that they both bind in the drug-binding pocket with similar docking scores and possibly interact with similar residues. Thus, we demonstrate that BD-CsA is a sensitive fluorescent substrate of P-gp that can be used to efficiently study the transporter's localization and function in vitro and in vivo. SIGNIFICANCE STATEMENT: The goal of this study was to develop an effective probe to study drug transport by P-glycoprotein (P-gp). Fluorophore-conjugated substrates are useful to study the P-gp transport mechanism, structural characteristics, and development of its inhibitors. Cyclosporine A (CsA), a cyclic peptide comprising 11 amino acids, is a known substrate of P-gp. P-gp affects CsA pharmacokinetics and interactions with other coadministered drugs, especially during transplant surgeries and treatment of autoimmune disorders, when CsA is given as an immunosuppressive agent. We synthesized and characterized Bodipy-FL-CsA as an avid fluorescent substrate that can be used to study the function of P-gp both in vitro and in vivo. We demonstrate that Bodipy-FL-conjugation does not affect the properties of CsA as a P-gp substrate.

Natural product drug delivery: A special challenge?

Natural products have a long-standing and critical role in drug development and medical use. The structural and physicochemical properties of natural products, while derived evolutionarily to be effective in living systems, may create challenges in translation to a pharmaceutical product. Molecular complexity, low solubility, functional group reactivity and general instability are among the challenges that typically need to be overcome. This review looks at some of the ways that natural products have been formulated and delivered to enable the successful application of these vitally important medicines to patients.

Mitochondria-targeted cyclosporin A delivery system to treat myocardial ischemia reperfusion injury of rats.

BACKGROUND: Cyclosporin A (CsA) is a promising therapeutic drug for myocardial ischemia reperfusion injury (MI/RI) because of its definite inhibition to the opening of mitochondrial permeability transition pore (mPTP). However, the application of cyclosporin A to treat MI/RI is limited due to its immunosuppressive effect to other normal organ and tissues. SS31 represents a novel mitochondria-targeted peptide which can guide drug to accumulate into mitochondria. In this paper, mitochondria-targeted nanoparticles (CsA@PLGA-PEG-SS31) were prepared to precisely deliver cyclosporin A into mitochondria of ischemic cardiomyocytes to treat MI/RI. RESULTS: CsA@PLGA-PEG-SS31 was prepared by nanoprecipitation. CsA@PLGA-PEG-SS31 showed small particle size (~ 50 nm) and positive charge due to the modification of SS31 on the surface of nanoparticles. CsA@PLGA-PEG-SS31 was stable for more than 30 days and displayed a biphasic drug release pattern. The in vitro results showed that the intracellular uptake of CsA@PLGA-PEG-SS31 was significantly enhanced in hypoxia reoxygenation (H/R) injured H9c2 cells. CsA@PLGA-PEG-SS31 delivered CsA into mitochondria of H/R injured H9c2 cells and subsequently increased the viability of H/R injured H9c2 cell through inhibiting the opening of mPTP and production of reactive oxygen species. In vivo results showed that CsA@PLGA-PEG-SS31 accumulated in ischemic myocardium of MI/RI rat heart. Apoptosis of cardiomyocyte was alleviated in MI/RI rats treated with CsA@PLGA-PEG-SS31, which resulted in the myocardial salvage and improvement of cardiac function. Besides, CsA@PLGA-PEG-SS31 protected myocardium from damage by reducing the recruitment of inflammatory cells and maintaining the integrity of mitochondrial function in MI/RI rats. CONCLUSION: CsA@PLGA-PEG-SS31 exhibited significant cardioprotective effects against MI/RI in rats hearts through protecting mitochondrial integrity, decreasing apoptosis of cardiomyocytes and myocardial infract area. Thus, CsA@PLGA-PEG-SS31 offered a promising therapeutic method for patients with acute myocardial infarction.