A limitation of using exosomes to their fullest potential is their limited secretion from cells, a major bottleneck to efficient exosome production and application. This is especially true for mesenchymal stem cells (MSCs), which can self-renew but have a limited expansion capacity, undergoing senescence after only a few passages, with exosomes derived from senescent stem cells showing impaired regenerative capacity compared to young cells. Here, we examined the effects of small molecule modulators capable of enhancing exosome secretion from MSCs. The treatment of MSCs with a combination of N-methyldopamine and norepinephrine robustly increased exosome production by three-fold without altering the ability of the MSC exosomes to induce angiogenesis, polarize macrophages to an anti-inflammatory phenotype, or downregulate collagen expression. These small molecule modulators provide a promising means to increase exosome production by MSCs.

A limitation to using exosomes to their fullest potential is their limited secretion from cells, a major bottleneck to efficient exosome production and application. This is especially true for mesenchymal stem cell (MSCs), which can self-renew but have limited expansion capacity, undergoing senescence after only a few passages, with exosomes derived from senescent stem cells showing impaired regenerative capacity compared to young cells. Here we examined the effects of small molecule modulators capable of enhancing exosome secretion from MSCs. Treatment of MSCs with a combination of methyldopamine and norepinephrine robustly increased exosome production by three-fold without altering the ability of the MSC exosomes to induce angiogenesis, polarize macrophages to the anti-inflammatory phenotype, or inhibit fibrosis. These small molecule modulators provide a promising means to increase exosome production by MSCs.

P58^IPK is a multifaceted endoplasmic reticulum (ER) chaperone and a regulator of eIF2α kinases involved in a wide range of cellular processes including protein synthesis, ER stress response, and macrophage-mediated inflammation. Systemic deletion of p58^IPK leads to age-related loss of retinal ganglion cells (RGC) and exacerbates RGC damage induced by ischemia/reperfusion and increased intraocular pressure (IOP), suggesting a protective role of p58^IPK in the retina. However, the mechanisms remain elusive. Herein, we investigated the cellular mechanisms underlying the neuroprotection action of p58^IPK using conditional knockout (cKO) mouse lines where p58^IPK is deleted in retinal neurons (Chx10-p58^IPK cKO) or in myeloid cells (Lyz2-p58^IPK cKO). In addition, we overexpressed p58^IPK by adeno-associated virus (AAV) in the retina to examine the effect of p58^IPK on RGC survival after ocular hypertension (OHT) in wild type (WT) mice. Our results show that overexpression of p58^IPK by AAV significantly improved RGC survival after OHT in WT mice, suggesting a protective effect of p58^IPK on reducing RGC injury. Conditional knockout of p58^IPK in retinal neurons or in myeloid cells did not alter retinal structure or cellular composition. However, a significant reduction in the b wave of light-adapted electroretinogram (ERG) was observed in Chx10-p58^IPK cKO mice. Deletion of p58^IPK in retinal neurons exacerbates RGC loss at 14 days after OHT. In contrast, deficiency of p58^IPK in myeloid cells increased the microglia/macrophage activation but had no effect on RGC loss. We conclude that deletion of p58^IPK in macrophages increases their activation, but does not influence RGC survival. These results suggest that the neuroprotective action of p58^IPK is mediated by its expression in retinal neurons, but not in macrophages. Therefore, targeting p58^IPK specifically in retinal neurons is a promising approach for the treatment of neurodegenerative retinal diseases including glaucoma.

This study aimed to understand the role of Interleukin-1β in mouse febrile seizures. To investigate the chronic effects of raised Interleukin-1β on seizures, the sodium currents of hippocampal neurons were recorded by whole-cell voltage clamp. Interleukin-1β inhibited sodium currents in mouse hippocampal neurons and verified that protein kinase C epsilon contributed to the effect of Interleukin-1β exposure. The inhibitory effect was also identified in neurons from a protein kinase C epsilon null mutant mouse. Action potentials were recorded using a ramp depolarizing current. Peak spike depolarization was significantly reduced by Interleukin-1β treatment, and was abolished following the administration of a protein kinase C epsilon inhibitor, εV1-2. However, neither Interleukin-1β nor εV12 had any significant effect on spike threshold. Interleukin1β reduced the amplitude of action potentials due to its inhibitory effect on sodium channels. This is hypothesised to decrease the release of presynaptic transmitters of neuroexcitability, thus exerting a neuroprotective role in excitotoxicity. To ascertain the role of protein kinase C epsilon on febrile seizures in vivo, a heated water-bath model was used to identify susceptible mice. It was found that protein kinase C epsilon reduced susceptibility to, and frequency of, febrile seizure onset. This may be related to the neuroprotective effect of Interleukin-1β on hippocampal neurons.