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Karasawa Y, Miyano K, Yamaguchi M, Nonaka M, Yamaguchi K, Iseki M, Kawagoe I, Uezono Y. Therapeutic Potential of Orally Administered Rubiscolin-6. Int J Mol Sci 2023; 24:9959. [PMID: 37373107 DOI: 10.3390/ijms24129959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/07/2023] [Accepted: 06/08/2023] [Indexed: 06/29/2023] Open
Abstract
Rubiscolins are naturally occurring opioid peptides derived from the enzymatic digestion of the ribulose bisphosphate carboxylase/oxygenase protein in spinach leaves. They are classified into two subtypes based on amino acid sequence, namely rubiscolin-5 and rubiscolin-6. In vitro studies have determined rubiscolins as G protein-biased delta-opioid receptor agonists, and in vivo studies have demonstrated that they exert several beneficial effects via the central nervous system. The most unique and attractive advantage of rubiscolin-6 over other oligopeptides is its oral availability. Therefore, it can be considered a promising candidate for the development of a novel and safe drug. In this review, we show the therapeutic potential of rubiscolin-6, mainly focusing on its effects when orally administered based on available evidence. Additionally, we present a hypothesis for the pharmacokinetics of rubiscolin-6, focusing on its absorption in the intestinal tract and ability to cross the blood-brain barrier.
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Affiliation(s)
- Yusuke Karasawa
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Pain Control Research, The Jikei University School of Medicine, Tokyo 105-8461, Japan
- Medical Affairs, Viatris Pharmaceuticals Japan Inc., Tokyo 105-0001, Japan
| | - Kanako Miyano
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Pain Control Research, The Jikei University School of Medicine, Tokyo 105-8461, Japan
- Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan
| | - Masahiro Yamaguchi
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Pain Control Research, The Jikei University School of Medicine, Tokyo 105-8461, Japan
- Medical Affairs, Pfizer Japan Inc., Tokyo 151-8589, Japan
| | - Miki Nonaka
- Department of Pain Control Research, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Keisuke Yamaguchi
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Anesthesiology and Pain Medicine, Faculty of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Masako Iseki
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Anesthesiology and Pain Medicine, Faculty of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Izumi Kawagoe
- Department of Anesthesiology and Pain Medicine, Faculty of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Yasuhito Uezono
- Department of Pain Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
- Department of Pain Control Research, The Jikei University School of Medicine, Tokyo 105-8461, Japan
- Department of Anesthesiology and Pain Medicine, Faculty of Medicine, Juntendo University, Tokyo 113-8421, Japan
- Supportive and Palliative Care Research Support Office, National Cancer Center Hospital East, Chiba 277-8577, Japan
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Jia ZK, Fu CX, Wang AL, Yao K, Chen XJ. Cataract-causing allele in CRYAA (Y118D) proceeds through endoplasmic reticulum stress in mouse model. Zool Res 2021; 42:300-309. [PMID: 33929105 PMCID: PMC8175955 DOI: 10.24272/j.issn.2095-8137.2020.354] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
As small heat shock proteins, α-crystallins function as molecular chaperones and inhibit the misfolding and aggregation of β/γ-crystallins. Genetic mutations of CRYAA are associated with protein aggregation and cataract occurrence. One possible process underlying cataract formation is that endoplasmic reticulum stress (ERS) induces the unfolded protein response (UPR), leading to apoptosis. However, the pathogenic mechanism related to this remains unexplored. Here, we successfully constructed a cataract-causing CRYAA (Y118D) mutant mouse model, in which the lenses of the CRYAA-Y118D mutant mice showed severe posterior rupture, abnormal morphological changes, and aberrant arrangement of crystallin fibers. Histological analysis was consistent with the clinical pathological characteristics. We also explored the pathogenic factors involved in cataract development through transcriptome analysis. In addition, based on key pathway analysis, up-regulated genes in CRYAA-Y118D mutant mice were implicated in the ERS-UPR pathway. This study showed that prolonged activation of the UPR pathway and severe stress response can cause proteotoxic and ERS-induced cell death in CRYAA-Y118D mutant mice.
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Affiliation(s)
- Zhe-Kun Jia
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Chen-Xi Fu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Ai-Ling Wang
- Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310020, China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China. E-mail:
| | - Xiang-Jun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China.,Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310020, China. E-mail:
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Ding L, Wang L, Yu Z, Ma S, Du Z, Zhang T, Liu J. Importance of Terminal Amino Acid Residues to the Transport of Oligopeptides across the Caco-2 Cell Monolayer. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:7705-7712. [PMID: 28812357 DOI: 10.1021/acs.jafc.7b03450] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The objective of this paper was to investigate the effects of terminal amino acids on the transport of oligopeptides across the Caco-2 cell monolayer. Ala-based tetra- and pentapeptides were designed, and the N- or C-terminal amino acid residues were replaced by different amino acids. The results showed that the oligopeptides had a wide range of transport permeability across the Caco-2 cell monolayer and could be divided into four categories: non-/poor permeability, low permeability, intermediate permeability, and good permeability. Tetrapeptides with N-terminal Leu, Pro, Ile, Cys, Met, and Val or C-terminal Val showed the highest permeability, with apparent permeability coefficient (Papp) values over 10 × 10-6 cm/s (p < 0.05), suggesting that nonpolar hydrophobic aliphatic amino acids or polar sulfur-containing amino acids were the best for the transport of tetrapeptides. Pentapeptides with N- or C-terminal Tyr also showed high permeability levels, with Papp values of about 10 × 10-6 cm/s. The amino acids Glu, Asn, and Thr at the N terminus or Lys, Asp, and Arg at the C terminus were also beneficial for the transport of tetra- and pentapeptides, with Papp values ranging from 1 × 10-6 to 10 × 10-6 cm/s. In addition, peptides with amino acids replaced at the N terminus generally showed higher permeability than those with amino acids replaced at the C terminus (p < 0.05), suggesting that N-terminal amino acids were more important for the transport of oligopeptides across the Caco-2 cell monolayer.
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Affiliation(s)
- Long Ding
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
| | - Liying Wang
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
| | - Zhipeng Yu
- College of Food Science and Engineering, Bohai University , Jinzhou, Liaoning 121013, People's Republic of China
| | - Sitong Ma
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
| | - Zhiyang Du
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
| | - Ting Zhang
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
| | - Jingbo Liu
- College of Food Science and Engineering, Jilin University , Changchun, Jilin 130062, People's Republic of China
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Lindqvist A, Jönsson S, Hammarlund-Udenaes M. Exploring Factors Causing Low Brain Penetration of the Opioid Peptide DAMGO through Experimental Methods and Modeling. Mol Pharm 2016; 13:1258-66. [DOI: 10.1021/acs.molpharmaceut.5b00835] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Annika Lindqvist
- Translational
PKPD Group, Department of Pharmaceutical Biosciences, Associate Member
of SciLife Lab, Uppsala University, Box 591, Uppsala, SE-75124, Sweden
| | - Siv Jönsson
- Pharmacometrics
Group, Department of Pharmaceutical Biosciences, Uppsala University, Box 591, Uppsala, SE-75124, Sweden
| | - Margareta Hammarlund-Udenaes
- Translational
PKPD Group, Department of Pharmaceutical Biosciences, Associate Member
of SciLife Lab, Uppsala University, Box 591, Uppsala, SE-75124, Sweden
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Vij R, Reddi S, Kapila S, Kapila R. Transepithelial transport of milk derived bioactive peptide VLPVPQK. Food Chem 2016. [DOI: 10.1016/j.foodchem.2015.05.121] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Kubo Y. [Carrier-mediated Transport of Cationic Drugs across the Blood-Tissue Barrier]. YAKUGAKU ZASSHI 2015; 135:1135-40. [PMID: 26423869 DOI: 10.1248/yakushi.15-00181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies of neurological dysfunction have revealed the neuroprotective effect of several cationic drugs, suggesting their usefulness in the treatment of neurological diseases. In the brain and retina, blood-tissue barriers such as blood-brain barrier (BBB) and blood-retinal barrier (BRB) are formed to restrict nonspecific solute transport between the circulating blood and neural tissues. Therefore study of cationic drug transport at these barriers is essential to achieve systemic delivery of neuroprotective agents into the neural tissues. In the retina, severe diseases such as diabetic retinopathy and macular degeneration can cause neurological dysfunction that dramatically affects patients' QOL. The BRB is formed by retinal capillary endothelial cells (inner BRB) and retinal pigment epithelial cells (outer BRB). Blood-to-retina transport of cationic drugs was investigated at the inner BRB, which is known to nourish two thirds of the retina. Blood-to-retinal transport of verapamil suggested that the barrier function of the BRB differs from that of the BBB. Moreover, carrier-mediated transport of verapamil and pyrilamine revealed the involvement of novel organic cation transporters at the inner BRB. The identified transport systems for cationic drugs are sensitive to several cationic neuroprotective and anti-angiogenic agents such as clonidine and propranolol, and the involvement of novel transporters was also suggested in their blood-to-retina transport across the inner BRB.
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Affiliation(s)
- Yoshiyuki Kubo
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama
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Rowe-Rendleman CL, Durazo SA, Kompella UB, Rittenhouse KD, Di Polo A, Weiner AL, Grossniklaus HE, Naash MI, Lewin AS, Horsager A, Edelhauser HF. Drug and gene delivery to the back of the eye: from bench to bedside. Invest Ophthalmol Vis Sci 2014; 55:2714-30. [PMID: 24777644 DOI: 10.1167/iovs.13-13707] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Osborne S, Chen W, Addepalli R, Colgrave M, Singh T, Tran C, Day L. In vitrotransport and satiety of a beta-lactoglobulin dipeptide and beta-casomorphin-7 and its metabolites. Food Funct 2014; 5:2706-18. [DOI: 10.1039/c4fo00164h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In vitrotransport of β-CM7 occurs through rapid hydrolysis into three peptide metabolites that transport at variable rates.
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Affiliation(s)
- Simone Osborne
- CSIRO Animal, Food and Health Sciences
- St Lucia, Australia
| | - Wei Chen
- CSIRO Animal, Food and Health Sciences
- St Lucia, Australia
| | - Rama Addepalli
- CSIRO Animal, Food and Health Sciences
- St Lucia, Australia
| | | | - Tanoj Singh
- CSIRO Animal, Food and Health Sciences
- Werribee, Australia
| | - Cuong Tran
- CSIRO Animal, Food and Health Sciences
- Adelaide, Australia
| | - Li Day
- CSIRO Animal, Food and Health Sciences
- Werribee, Australia
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Sreekumar PG, Chothe P, Sharma KK, Baid R, Kompella U, Spee C, Kannan N, Manh C, Ryan SJ, Ganapathy V, Kannan R, Hinton DR. Antiapoptotic properties of α-crystallin-derived peptide chaperones and characterization of their uptake transporters in human RPE cells. Invest Ophthalmol Vis Sci 2013; 54:2787-98. [PMID: 23532520 PMCID: PMC3632268 DOI: 10.1167/iovs.12-11571] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 03/19/2013] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The chaperone proteins, α-crystallins, also possess antiapoptotic properties. The purpose of the present study was to investigate whether 19 to 20-mer α-crystallin-derived mini-chaperone peptides (α-crystallin mini-chaperone) are antiapoptotic, and to identify their putative transporters in human fetal RPE (hfRPE) cells. METHODS Cell death and caspase-3 activation induced by oxidative stress were quantified in early passage hfRPE cells in the presence of 19 to 20-mer αA- or αB-crystallin-derived or scrambled peptides. Cellular uptake of fluorescein-labeled, α-crystallin-derived mini-peptides and recombinant full-length αB-crystallin was determined in confluent hfRPE. The entry mechanism in hfRPE cells for α-crystallin mini-peptides was investigated. The protective role of polycaprolactone (PCL) nanoparticle encapsulated αB-crystallin mini-chaperone peptides from H2O2-induced cell death was studied. RESULTS Primary hfRPE cells exposed to oxidative stress and either αA- or αB-crystallin mini-chaperones remained viable and showed marked inhibition of both cell death and activation of caspase-3. Uptake of full-length αB-crystallin was minimal while a time-dependent uptake of αB-crystallin-derived peptide was observed. The mini-peptides entered the hfRPE cells via the sodium-coupled oligopeptide transporters 1 and 2 (SOPT1, SOPT2). PCL nanoparticles containing αB-crystallin mini-chaperone were also taken up and protected hfRPE from H2O2-induced cell death at significantly lower concentrations than free αB-crystallin mini-chaperone peptide. CONCLUSIONS αA- and αB-crystallin mini-chaperones offer protection to hfRPE cells and inhibit caspase-3 activation. The oligopeptide transporters SOPT1 and SOPT2 mediate the uptake of these peptides in RPE cells. Nanodelivery of αB-crystallin-derived mini-chaperone peptide offers an alternative approach for protection of hfRPE cells from oxidant injury.
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Affiliation(s)
| | - Paresh Chothe
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia
| | - Krishna K. Sharma
- Department of Ophthalmology, University of Missouri-Columbia School of Medicine, Columbia, Missouri
| | - Rinku Baid
- Departments of Pharmaceutical Sciences and Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Uday Kompella
- Departments of Pharmaceutical Sciences and Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Christine Spee
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Nandini Kannan
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Christina Manh
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Stephen J. Ryan
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia
| | - Ram Kannan
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - David R. Hinton
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California
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Ananth S, Thakkar SV, Gnana-Prakasam JP, Martin PM, Ganapathy PS, Smith SB, Ganapathy V. Transport of the synthetic opioid peptide DADLE ([D-Ala2,D-Leu5]-enkephalin) in neuronal cells. J Pharm Sci 2011; 101:154-63. [PMID: 21905028 DOI: 10.1002/jps.22733] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 07/07/2011] [Accepted: 08/02/2011] [Indexed: 01/08/2023]
Abstract
The sodium-coupled oligopeptide transporters 1 and 2 (SOPT1 and SOPT2) transport peptides consisting of at least five amino acids and show potential for the delivery of therapeutically relevant peptides/peptidomimetics. Here, we examined the expression of these two transporters in the retinal neuronal cell line RGC-5. These cells showed robust uptake activity for the synthetic pentapeptide DADLE ([D-Ala(2),D-Leu(5)]-Enkephalin). The uptake was Na(+) dependent and saturable (K(t), 6.2 ± 0.6 μM). A variety of oligopeptides inhibited DADLE uptake. The uptake of the competing oligopeptides was directly demonstrated with fluorescein isothiocyanate-labeled Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys in RGC-5 cells and primary mouse retinal ganglion cells. The characteristics of DADLE uptake matched those of SOPT2. We then examined the expression of SOPT1 in these cells with deltorphin II (Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH(2)) as the substrate and found that RGC-5 cells also expressed SOPT1. As it is already known that SOPT1 is expressed in the neuronal cell line SK-N-SH, we investigated SOPT2 expression in these cells to determine whether the presence of both oligopeptide transporters is a common feature of neuronal cells. These studies showed that SK-N-SH cells also expressed SOPT2. This constitutes the first report on the functional characterization of SOPT1 and SOPT2 in retinal neuronal cells and on the expression of SOPT2 in nonretinal neuronal cells.
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Affiliation(s)
- Sudha Ananth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, USA
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Chothe P, Singh N, Ganapathy V. Evidence for two different broad-specificity oligopeptide transporters in intestinal cell line Caco-2 and colonic cell line CCD841. Am J Physiol Cell Physiol 2011; 300:C1260-9. [PMID: 21307350 DOI: 10.1152/ajpcell.00299.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Recently the existence of two different Na(+)-coupled oligopeptide transport systems has been described in mammalian cells. These transport systems are distinct from the previously known H(+)/peptide cotransporters PEPT1 and PEPT2, which transport only dipeptides and tripeptides. To date, the only peptide transport system known to exist in the intestine is PEPT1. Here we investigated the expression of the Na(+)-coupled oligopeptide transporters in intestinal cell lines, using the hydrolysis-resistant synthetic oligopeptides deltorphin II and [d-Ala(2),d-Leu(5)]enkephalin (DADLE) as model substrates. Caco-2 cells and CCD841 cells, both representing epithelial cells from human intestinal tract, were able to take up these oligopeptides. Uptake of deltorphin II was mostly Na(+) dependent, with more than 2 Na(+) involved in the uptake process. In contrast, DADLE uptake was only partially Na(+) dependent. The uptake of both peptides was also influenced by H(+) and Cl(-), although to a varying degree. The processes responsible for the uptake of deltorphin II and DADLE could be differentiated not only by their Na(+) dependence but also by their modulation by small peptides. Several dipeptides and tripeptides stimulated deltorphin II uptake but inhibited DADLE uptake. These modulating small peptides were, however, not transportable substrates for the transport systems that mediate deltorphin II or DADLE uptake. These two oligopeptide transport systems were also able to take up several nonopioid oligopeptides, consisting of 9-17 amino acids. This represents the first report on the existence of transport systems in intestinal cells that are distinct from PEPT1 and capable of transporting oligopeptides consisting of five or more amino acids.
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Affiliation(s)
- Paresh Chothe
- Dept. of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA
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Chothe PP, Gnana-Prakasam JP, Ananth S, Martin PM, Kannan R, Hinton DR, Smith SB, Ganapathy V. Transport of hepcidin, an iron-regulatory peptide hormone, into retinal pigment epithelial cells via oligopeptide transporters and its relevance to iron homeostasis. Biochem Biophys Res Commun 2011; 405:244-9. [PMID: 21219868 DOI: 10.1016/j.bbrc.2011.01.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 01/05/2011] [Indexed: 12/16/2022]
Abstract
Retinal pigment epithelial cells (RPE) express two transport systems (SOPT1 and SOPT2) for oligopeptides. Hepcidin is an iron-regulatory peptide hormone consisting of 25 amino acids. This hormone binds to ferroportin, an iron exporter expressed on the cell surface, and facilitates its degradation. Here we investigated if hepcidin is a substrate for SOPT1 and SOPT2 and if the hormone has any intracellular function in RPE. Hepcidin inhibited competitively the uptake of deltorphin II (a synthetic oligopeptide substrate for SOPT1) and DADLE (a synthetic oligopeptide substrate for SOPT2) with IC50 values in the range of 0.4-1.7 μM. FITC-hepcidin was taken up into RPE, and this uptake was inhibited by deltorphin II and DADLE. The entry of FITC-hepcidin into cells was confirmed by flow cytometry. Incubation of RPE with hepcidin decreased the levels of ferroportin mRNA. This effect was not a consequence of hepcidin-induced ferroportin degradation because excessive iron accumulation in RPE, which is expected to occur in these cells as a result of ferroportin degradation, did not decrease but instead increased the levels of ferroportin mRNA. This study reveals for the first time a novel intracellular function for hepcidin other than its established cell surface action on ferroportin.
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Affiliation(s)
- Paresh P Chothe
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA, USA
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