The humanin peptide mediates ELP nanoassembly and protects human retinal pigment epithelial cells from oxidative stress

Abstract

Humanin (HN) is a hydrophobic 24-amino acid peptide derived from mitochondrial DNA that modulates cellular responses to oxidative stress and protects human retinal pigment epithelium (RPE) cells from apoptosis. To solubilize HN, this report describes two genetically-encoded fusions between HN and elastin-like polypeptides (ELP). ELPs provide steric stabilization and/or thermo-responsive phase separation. Fusions were designed to either remain soluble or phase separate at the physiological temperature of the retina. Interestingly, the soluble fusion assembles stable colloids with a hydrodynamic radius of 39.1 nm at 37 °C. As intended, the thermoresponsive fusion forms large coacervates (> 1,000 nm) at 37 °C. Both fusions bind human RPE cells and protect against oxidative stress-induction of apoptosis (TUNEL, caspase-3 activation). Their activity is mediated through STAT3; furthermore, STAT3 inhibition eliminates their protection. These findings suggest that HN polypeptides may facilitate cellular delivery of biodegradable nanoparticles with potential protection against age-related diseases, including macular degeneration.

Humanin Ameliorates Free Fatty Acid-Induced Endothelial Inflammation by Suppressing the NLRP3 Inflammasome

“…Recent discoveries have shown that humanin protects retinal pigment epithelium cells from oxidative stress. 28 In this study, we observed that humanin can suppress oxidative stress by inhibiting the production of ROS induced by FFA in HAECs. Interestingly, the effect of humanin on the production of ROS may be mediated through downregulating the expression of NOX2.…”

Mechanisms of protection of retinal pigment epithelial cells from oxidant injury by humanin and other mitochondrial-derived peptides: Implications for age-related macular degeneration

“…Several studies have demonstrated that HN is a potent cytoprotective peptide for several cells exposed to different cell stressors. These include serum deprivation [ 69 ], stroke [ 70 , 71 ], N-methyl- d -aspartate-induced excitotoxicity [ 72 ], Aβ oligomers [ 37 , 56 , [73] , [74] , [75] ], tert-butyl hydroperoxide (tBH)-induced stress [ 35 , 40 ], endoplasmic reticulum (ER)-stress [ 36 , 41 ], and oxidized low-density lipoprotein induced apoptosis [ 76 ]. HN binds to Bax and prevents the release of cytochrome c from the mitochondria, thereby preventing apoptosis [ 63 , 77 ].…”

“…HN mediates its function via intracellular or mitochondria-dependent and extracellular or receptor-mediated pathways [ 35 , 40 , 63 , 124 ]. One extracellular mechanism by which HN elicits its action is through binding to its membrane receptors, namely trimeric receptor complex and the formyl peptide receptor like-1 (FPRL-1) receptor [ 65 , 124 , 125 ].…”

“…Dimerization and DNA binding of STAT3 requires phosphorylation of its Tyr705 site, and dimerized STATs move to the nucleus and regulate gene transcription. Blocking the STAT3 signaling pathway with STAT3 inhibitor significantly diminished the protective effect of HN in oxidant-induced cells, irrespective of whether the RPE cells are treated with the plain peptide or HN- elastin-like polypeptide (ELP) nanoparticle fusion protein [ 35 , 40 ]. The protective effect with plain HN peptide, though significant, was only partial; thus, one can assume that the receptor-mediated effects of HN peptide only partially contributed to the prevention of cell death.…”

“…The 12S rRNA region produces another MDP known as mitochondrial open reading frame (ORF) of the twelve S c (MOTS-c). Since most of these MDPs show cytoprotective functions in RPE and other cell types [ [35] , [36] , [37] , [38] , [39] , [40] , [41] ], damage to 16S rRNA or 12S rRNA could result in dysregulated production of this cytoprotective peptide. The mitochondrial genome has a very high mutation rate, 10- to 17-fold higher than that observed in nuclear DNA [ 42 ].…”