Peptides derived from the heptad repeat 2 (HR2) region of the HIV fusogenic protein gp41 are potent inhibitors of viral infection, and one of them, enfuvirtide, is used for the treatment of therapyexperienced AIDS patients. The mechanism of action of these peptides is binding to a critical intermediate along the virus-cell fusion pathway, and accordingly, increasing the affinity for the intermediate yields more potent inhibitors. We took a different approach, namely to increase the potency of the HR2 peptide inhibitor C34 by targeting it to the cell compartment where fusion occurs, and we show here that a simple, yet powerful way to accomplish this is attachment of a cholesterol group. C34 derivatized with cholesterol (C34-Chol) shows dramatically increased antiviral potency on a panel of primary isolates, with IC 90 values 15-to 300-fold lower than enfuvirtide and the second-generation inhibitor T1249, making C34-Chol the most potent HIV fusion inhibitor to date. Consistent with its anticipated mechanism of action, the antiviral activity of C34-Chol is unusually persistent: washing target cells after incubation with C34-Chol, but before triggering fusion, increases IC 50 only 7-fold, relative to a 400-fold increase observed for C34. Moreover, derivatization with cholesterol extends the half-life of the peptide in vivo. In the mouse, s.c. administration of 3.5 mg/kg C34-Chol yields a plasma concentration 24 h after injection >300-fold higher than the measured IC 90 values. Because the fusion machinery targeted by C34-Chol is similar in several other enveloped viruses, we believe that these findings may be of general utility. antiretroviral drug ͉ enveloped viruses ͉ lipid rafts ͉ peptide therapeutic

Background Cardiac progenitors (CPC) mediate cardioprotection via paracrine effects. To date, most of studies focused on secreted paracrine proteins. Here we investigated the CPC-derived-exosomes on protecting myocardium from acute ischemia/reperfusion (MI/R) injury. Methods and Results CPC were isolated from mouse heart using two-step protocol. Exosomes were purified from conditional medium, and confirmed by electron micrograph and Western blot using CD63 as a marker. qRT-PCR shows that CPC- exosomes have high level expression of GATA4-responsive-miR-451. Exosomes were ex vivo labeled with PKH26, We observed exosomes can be uptaken by H9C2 cardiomyoblasts with high efficiency after 12 hours incubation. CPC-exosomes protect H9C2 from oxidative stress by inhibiting caspase 3/7 activation in vitro. In vivo delivery of CPC-exosomes in an acute mouse myocardial ischemia/reperfusion model inhibited cardiomyocyte apoptosis by about 53% in comparison with PBS control(p<0.05). Conclusion Our results suggest, for the first time, the CPC-exosomes can be used as a therapeutic vehicle for cardioprotection, and highlights a new perspective for using non-cell exosomes for cardiac disease.

Background/Objectives Induced pluripotent stem cells (iPS) exhibit enhanced survival and proliferation in ischemic tissues. However, the therapeutic application of iPS cells is limited by their tumorigenic potential. We hypothesized that iPS cells can transmit cytoprotective signals to cardiomyocytes via exosomes/microvesicles. Methods Exosomes/microvesicles secreted from mouse cardiac fibroblast (CF)-derived iPS cells (iPS-exo) were purified from conditioned medium and confirmed by electron micrograph, size distribution and zeta potential by particle tracking analyzer and protein expression of the exosome markers CD63 and Tsg101. Results We observed that exosomes are at low zeta potential, and easily aggregate. Temperature affects zeta potential (−14~−15mV at 23°C vs −24mV at 37°C). The uptake of iPS-exo protects H9C2 cells against H2O2-induced oxidative stress by inhibiting caspase 3/7 activation (P<0.05, n=6). Importantly, iPS-exo treatment can protect against myocardial ischemia/reperfusion (MIR) injury via intramyocardially injection into mouse ischemic myocardium before reperfusion. Furthermore, iPS-exo deliver cardioprotective miRNAs, including nanog-regulated miR-21 and HIF-1α-regulated miR-210, to H9C2 cardiomyocytes in vitro. Conclusions exosomes/microvesicles secreted by iPS cells are very effective at transmitting cytoprotective signals to cardiomyocytes in the setting of MIR. iPS-exo thus represent novel biological nanoparticles that offer the benefits of iPS cell therapy without the risk of tumorigenicity and can potentially serve as an “ off-the-shelf” therapy to rescue ischemic cardiomyocytes in conditions such as MIR.