Transduction of functionally active TAT fusion proteins into cornea

A Nanogel Formulation of Anti-VEGF Peptide for Ocular Neovascularization Treatment

Age-related macular degeneration (AMD) is an eye disorder that can lead to visual impairment in elder patients, and current treatments include repeated injections of monoclonal antibody-based antivascular endothelial growth factor (anti-VEGF) agents. This study investigates the potential of a nanoformulation of a peptide anti-VEGF molecule for neovascular AMD. Anti-VEGF peptide HRHTKQRHTALH (HRH), which has high affinity to VEGF-Fc receptor, was used as the bioactive agent to control neovascularization of the retina. The nanoformulation consisting of hyaluronic acid nanogel was generated by incorporating divinyl sulfone and cholesterol to increase the stability and control the size of the nanodrug. The encapsulation efficacy of nanogel was 65%, and drug release was 34.72% at the end of 192 h. Obtained nanogels were efficiently internalized in 15 min by human umbilical vascular endothelial cells (HUVECs) and ARPE-19 cells, and results indicate that nanoformulation is not toxic to ARPE-19 cells, whereas it inhibits HUVEC proliferation owing to anti-VEGF peptide in the nanogel structure. In the coculture experiment in which retinal penetration was modeled, it was observed that the nanogel reached HUVECs and negatively affected their proliferation without disturbing the monolayer of ARPE-19 cells. In vivo experiments with chick chorioallantoic membrane revealed that nanogel formulation has higher antiangiogenesis activity compared to free HRH. Additionally, in an oxygen-induced retinopathy model, the excessive growth of blood vessels was notably suppressed in mice treated with HRH-loaded nanogel. This research indicates that nanogels formulated in this study are promising candidates as a topical treatment for AMD.

Protein and polypeptide mediated delivery to the eye

Hybrid or recombinant protein-polymers, peptide-based biomaterials, and antibody-targeted therapeutics are widely explored for various ocular conditions and vision correction. They have been noted for their potential biocompatibility, potency, adaptability, and opportunities for sustained drug delivery. Unique to peptide and protein therapeutics, their production by cellular translation allows their precise modification through genetic engineering. To a greater extent than drug delivery to other systems, delivery to the eye can benefit from the combination of locally-targeted administration and protein-based specificity. Consequently, a range of delivery platforms and administration methods have been exploited to address the ocular delivery of peptide and protein biomaterials. This review discusses a sample of preclinical and clinical opportunities for peptide-based drug delivery to the eye.

Overcoming negatively charged tissue barriers: Drug delivery using cationic peptides and proteins

Negatively charged tissues are ubiquitous in the human body and are associated with a number of common diseases yet remain an outstanding challenge for targeted drug delivery. While the anionic proteoglycans are critical for tissue structure and function, they make tissue matrix dense, conferring a high negative fixed charge density (FCD) that makes drug penetration through the tissue deep zones and drug delivery to resident cells extremely challenging. The high negative FCD of these tissues is now being utilized by taking advantage of electrostatic interactions to create positively charged multi-stage delivery methods that can sequentially penetrate through the full thickness of tissues, create a drug depot and target cells. After decades of work on attempting delivery using strong binding interactions, significant advances have recently been made using weak and reversible electrostatic interactions, a characteristic now considered essential to drug penetration and retention in negatively charged tissues. Here we discuss these advances using examples of negatively charged tissues (cartilage, meniscus, tendons and ligaments, nucleus pulposus, vitreous of eye, mucin, skin), and delve into how each of their structures, tissue matrix compositions and high negative FCDs create barriers to drug entry and explore how charge interactions are being used to overcome these barriers. We review work on tissue targeting cationic peptide and protein-based drug delivery, compare and contrast drug delivery designs, and also present examples of technologies that are entering clinical trials. We also present strategies on further enhancing drug retention within diseased tissues of lower FCD by using synergistic effects of short-range binding interactions like hydrophobic and H-bonds that stabilize long-range charge interactions. As electrostatic interactions are incorporated into design of drug delivery materials and used as a strategy to create properties that are reversible, tunable and dynamic, bio-electroceuticals are becoming an exciting new direction of research and clinical work.

Cell penetrating peptides in ocular drug delivery: State of the art

Despite the increasing number of effective therapeutics for eye diseases, their treatment is still challenging due to the presence of effective barriers protecting eye tissues. Cell Penetrating Peptides (CPPs), synthetic and natural short amino acid sequences able to cross cellular membrane thanks to a transduction domain, have been proposed as possible enhancing strategies for ophthalmic delivery. In this review, a general description of CPPs classes, design approaches and proposed cellular uptake mechanisms will be provided to the reader as an introduction to ocular CPPs application, together with an overview of the main problems related to ocular administration. The results obtained with CPPs for the treatment of anterior and posterior segment eye diseases will be then introduced, with a focus on non-invasive or minimally invasive administration, shifting from CPPs capability to obtain intracellular delivery to their ability to cross biological barriers. The problems related to in vitro, ex vivo and in vivo models used to investigate CPPs mediated ocular delivery will be also addressed together with potential ocular toxicity issues.

Replacement of the C6ORF66 assembly factor (NDUFAF4) restores complex I activity in patient cells

Disorders of the oxidative phosphorylation (OXPHOS) system frequently result in a severe multisystem disease with the consequence of early childhood death. Among these disorders, isolated complex I deficiency is the most frequently diagnosed, accounting for one-third of all cases of respiratory chain deficiency. We chose to focus on complex I deficiency, caused by mutation in the assembly factor chromosome 6, open reading frame 66 (C6ORF66; NADH dehydrogenase [ubiquinone] complex I assembly factor 4 [NDUFAF4]) protein. We used the approach of cell- and organelle-directed protein/enzyme replacement therapy, with the transactivator of transcription (TAT) peptide as the moiety delivery system. This step will enable us to deliver the wild-type assembly factor C6ORF66 into patient cells and their mitochondria, leading to the proper assembly and function of complex I and, as a result, to a functional OXPHOS system. We designed and constructed the TAT-ORF fusion protein by gene fusion techniques, expressed the protein in an Escherichia coli expression system and highly purified it. Our results indicate that TAT-ORF enters patients' cells and their mitochondria rapidly and efficiently. TAT-ORF is biologically active and led to an increase in complex I activity. TAT-ORF also increased the number of patient cells and improved the activity of their mitochondria. Moreover, we observed an increase in ATP production, a decrease in the content of mitochondria and a decrease in the level of reactive oxygen species. Our results suggest that this approach of protein replacement therapy for the treatment of mitochondrial disorders is a promising one.

Mechanisms of viral infections associated with HIV: workshop 2B

HIV infection is commonly associated with activation and dissemination of several other viral pathogens, including herpes simplex virus 1/2, human cytomegalovirus, human herpesvirus 8, Epstein-Barr virus, Varicella Zoster virus, and human papillomavirus, which behave as opportunistic agents and cause various diseases in immunocompromised hosts. The increased frequency and severity of diseases caused by these viruses in HIV-infected individuals is due mainly to dysfunction of both the adaptive and innate immune responses to viral pathogens. In addition, molecular interactions between HIV and these opportunistic viruses are likely to play critical roles in the progression of disease, including neoplasia. This report reviews the critical aspects of HIV interaction with opportunistic viruses, including Epstein-Barr virus, human cytomegalovirus, herpes simplex virus, Varicella Zoster virus, human herpesvirus 8, and human papillomavirus.

Cell-penetrating peptide TAT-mediated delivery of acidic FGF to retina and protection against ischemia-reperfusion injury in rats

The development of non-invasive ocular drug delivery systems is of practical importance in the treatment of retinal disease. In this study, we evaluated the efficacy of transactivator of transcription protein transduction domain (TAT-PTD, TAT(49-57)) as a vehicle to deliver acidic FGF (aFGF) to retina in rats. TAT-conjugated aFGF-His (TAT-aFGF-His) exhibited efficient penetration into the retina following topical administration to the ocular surface. Immunochemical staining with anti-His revealed that TAT-aFGF-His proteins were readily found in the retina (mainly in the ganglion cell layer) at 30 min. and remained detectable for at least 8 hrs after administration. In contrast, His(+) proteins were undetectable in the retina after topical administration of aFGF-His, indicating that aFGF-His cannot penetrate the ocular barrier. Furthermore, TAT-aFGF-His, but not aFGF-His, mediated significant protection against retinal ischemia-reperfusion (IR) injury. After IR injury, retina from TAT-aFGF-His-treated rats showed better-maintained inner retinal layer structure, reduced apoptosis of retinal ganglion cells and improved retinal function compared to those treated with aFGF-His or PBS. These results indicate that conjugation of TAT to aFGF-His can markedly improve the ability of aFGF-His to penetrate the ocular barrier without impairing its biological function. Thus, TAT(49-57) provides a potential vehicle for efficient drug delivery in the treatment of retinal disease.

A heat shock protein 90 binding domain in endothelial nitric-oxide synthase influences enzyme function

Previous reports suggest heat shock protein 90 (hsp90) associates with endothelial nitric-oxide synthase (eNOS) to increase nitric oxide (*NO) generation. Ansamycin inhibition of chaperone-dependent activity increases eNOS generation of superoxide anion (O(2)(*)) upon enzyme activation. In the present study we identify where hsp90 binds to eNOS using overlapping decoy peptides based on the amino acid (aa) sequence of eNOS (291-420). B1, B2, and B3 peptides inhibited hsp90 association with eNOS in cell lysates from proliferating bovine aortic endothelial cells. B2 (aa 301-320), common to both B1 and B3, decreased stimulated *NO production and hsp90 association in bovine aortic endothelial cells. The B2/B3 peptide was redesigned to TSB2 that includes a TAT protein transduction domain and shortened to 14 aa. TSB2 impaired vasodilation of isolated facialis arteries in vitro and in vivo and increased eNOS-dependent O(2)(*) generation in native endothelial cells on mouse aortas, whereas a control peptide, TSB(Ctr), which has the four glutamic acids in TSB2 substituted with alanine, showed no such effects. Site-directed mutagenesis of eNOS at 310, 314, 318, and 323 Glu to Ala yields an eNOS mutant that exhibited reduced hsp90 association and generated O(2)(*) rather than *NO upon activation. Together, these data demonstrate that hsp90 associates with eNOS at aa 310-323. Moreover, a decoy peptide based on this sequence is sufficient to displace hsp90 from eNOS and uncouple eNOS activity from *NO generation. Thus, Glu-310, Glu-314, Glu-318, and Glu-323 in eNOS, although each does not do much by itself, synergistically they increase "cooperativity" in the association step that is critical for maintaining hsp90-eNOS interactions and promoting coupled eNOS activity. Such chaperone-dependent signaling may play an important role in modulating the balance of *NO and O(2)(*) generation from eNOS and, therefore, vascular function.

Hypotensive effect of profilin on rabbit intraocular pressure

Ocular hypertension is a negative process that occurs within the eye and is the main risk factor to develop glaucoma, a progressive loss of vision due to degeneration of retinal ganglion cells. The protein transduction technique allows a cargo to cross biological membranes. Using this technique we have previously shown that a membrane permeable version of profilin I (PTD4-profilin) increased aqueous humour outflow facility. Here we have investigated if a topical application of PTD4-profilin was able to modify intraocular pressure in rabbits. 10 microM PTD4-profilin (10 microL), reduced intraocular pressure by 20% compared to the control vehicle, this value being in the range of other commercial drugs, which produced intraocular pressure reductions between 18 and 35%. The mean-time effect for PTD4-profilin was 6.8 h and was also in the same range as commercial products that provided values between 4.3 and 5.5 h. According to the results presented here we propose PTD4-profilin as a new approach for the treatment of ocular hypertension and PTD4 as a new strategy to facilitate the penetration of molecules into the eye.

D-TAT transporter as an ocular peptide delivery system

BACKGROUND

Future treatment for genetic diseases may involve the replacement of malfunctioning genes through virus-mediated gene therapy. However, this approach is plagued with many problems, both ethical and scientific. Therefore, alternative treatments based on new molecules may represent a safer option. Molecular treatment of many eye diseases will need to bring active molecules into the photoreceptors. Recently, the trans-activator protein (TAT) human immunodeficiency virus type 1 (HIV-1) transcriptional factor has proven to be effective in transporting molecules across cellular membranes. The half-life of these molecules does not exceed 48 hours. The potential use of the retro-inverso form of the TAT (D-TAT) peptide, the protein transducing domain of the HIV-1 transcriptional factor, as a molecular transporter was investigated.

METHODS

FITC-labelled D-TAT (D-TAT FITC) was applied to the 661W murine photoreceptor cell line in culture. The labelled peptide was also injected into the vitreous body or the subretinal space of adult mice. Cells and cryosections of eyes were analysed under fluorescence microscopy at various time points after peptide treatment. Coimmunostaining with various antibodies was performed in order to characterize the transduces cells.

RESULTS

D-TAT was effective in transducing photoreceptor cells in culture. Transduction of D-TAT FITC was also effective when injected into the vitreous or subretinal space and was observed for a longer period of time than L-TAT FITC.

CONCLUSIONS

The retro-inverso form of the TAT sequence is effective in transducing cells from various compartments of the eye. After 14 days, the D-TAT FITC was clearly visible in the retina whereas L-TAT FITC had almost disappeared. The D-TAT peptide represents an interesting molecular transporter that, when coupled to a specific effector, may have potential therapeutic future, especially when a long-lasting action is needed.