A PEDF peptide mimetic effectively relieves dry eye in a diabetic murine model by restoring corneal nerve, barrier, and lacrimal gland function.

PURPOSE: The study investigated effectiveness of a novel PEDF peptide mimetic to alleviate dry eye-like pathologies in a Type I diabetic mouse model established using streptozotocin. METHODS: Mice were treated topically for 3-6 weeks with Ppx (a 17-mer PEDF mimetic) 2x/day or vehicle. Corneal sensitivity, tear film, epithelial and endothelial injury were measured using Cochet-Bonnet esthesiometer, phenol red cotton thread wetting, fluorescein sodium staining, and ZO1 expression, respectively. Inflammatory and parasympathetic nerve markers and activation of the MAPK/JNK pathways in the lacrimal glands were measured. RESULTS: Diabetic mice exhibited features of dry eye including reduced corneal sensation and tear secretion and increased corneal epithelium injury, nerve degeneration, and edema. Ppx reversed these pathologies and restored ZO1 expression and morphological integrity of the endothelium. Upregulation of IL-1ß and TNFα, increased activation of P-38, JNK, and ERK, and higher levels of M3ACHR in diabetic lacrimal glands were also reversed by the peptide treatment. CONCLUSION: The study demonstrates that topical application of a synthetic PEDF mimetic effectively alleviates diabetes-induced dry eye by restoring corneal sensitivity, tear secretion, and endothelial barrier and lacrimal gland function. These findings have significant implications for the potential treatment of dry eye using a cost-effective and reproducible approach with minimal invasiveness and no obvious side effects.

Effect of PPARγ on oxidative stress in diabetes-related dry eye.

Oxidative stress is closely associated with diabetes and can cause free radical accumulation and eventually lead to ocular surface tissue damage. The purpose of this study was to investigate peroxisome proliferator-activated receptor-γ (PPARγ) expression in the lacrimal gland (LG), meibomian gland, and cornea of diabetes-related dry eye mice and whether the PPARγ agonist rosiglitazone can alleviate the oxidative stress of the ocular surface, thereby improving the condition of diabetes-related dry eye. Quantitative RT-PCR (Q-PCR) showed that the PPARγ, catalase, glutathione peroxidase 3, and heme oxygenase-1 (HO-1) mRNA expression levels in the LG of diabetes-related dry eye mice decreased at 8 and 12 weeks. In addition, the increased levels of oxidative stress were confirmed by western blot. Although the mRNA expression levels of antioxidant enzymes in the cornea and meibomian gland decreased at 8 weeks, some of them recovered by 12 weeks. Rosiglitazone alleviated ocular surface damage and increased corneal sensitivity and tear production in diabetes-related dry eye mice. Moreover, the reactive oxygen species accumulation was reduced and the PPARγ, HO-1, and glutathione peroxidase 3 mRNA expression levels were increased in the LG. The PPARγ, HO-1, translocase of the outer membrane 20, and mitochondrial transcription factor A protein levels were also significantly increased. These results demonstrated that rosiglitazone reduced oxidative stress in the LG of diabetes-related dry eye mice, at least in part, by activating PPARγ to up-regulate antioxidant enzyme expression.

Bradykinin receptor in immune-mediated renal tubular injury in trichloroethylene-sensitized mice: Impact on NF-κB signaling pathway.

Trichloroethylene (TCE) is known to induce skin disorders and multi-system dysfunction, but the mechanism of this multi-organ injury is not entirely clear. It was shown in a previous study that levels of pivotal end-products of the kallikrein-kinin system (KKS), i.e. bradykinin (BK) and BK receptors B1R/B2R, in the kidneys were increased by TCE exposure. Unfortunately, how BK and its receptors acted in the etiology of the induced renal injury is not clear. Thus, this study explored any correlation between BK receptors and immune renal injury in TCE-sensitized mice by blocking the BK receptors B1R/B2R. BALB/c mice were sensitized (via skin) by TCE, with or without pre-treatment with a B1R or B2R antagonist. Renal lesions, increased expressions of B1R, B2R, Kim-1, Lipocalin-2, and NF-κB p65 subunit on tubular epithelial cells were all observed in TCE-sensitized mice. Serum levels of creatinine (Cr), microglobulin α1 and ß2, along with mRNA levels for inflammatory cytokines and NF- κB p65 in kidneys, were all increased by 72 h after a final challenge. Highly selective antagonist pre-treatment blocked B2R and significantly attenuated TCE-induced changes. Blocking B1R or B2R attenuated release of pro-inflammatory cytokines and activation of NF-κB signaling pathway (as reflected in lower up-regulation of pIκB and nuclear NF-κB p65 subunit, and down-regulation of IκB in the kidneys. These results provided evidence that TCE-sensitization caused KKS activation and enhanced the expression of B1R and B2R on tubular epithelial cells. This, in turn, accelerated NF-κB signaling pathway activation and amplified inflammatory cytokine release, which all likely contributed to TCE-induced immune renal injury.

Gene expression and metabolite profiles of cotton fiber during cell elongation and secondary cell wall synthesis.

Cotton fibers elongate rapidly after initiation of elongation, eventually leading to the deposit of a large amount of cellulose. To reveal features of cotton fiber cells at the fast elongation and the secondary cell wall synthesis stages, we compared the respective transcriptomes and metabolite profiles. Comparative analysis of transcriptomes by cDNA array identified 633 genes that were differentially regulated during fiber development. Principal component analysis (PCA) using expressed genes as variables divided fiber samples into four groups, which are diagnostic of developmental stages. Similar grouping results are also found if we use non-polar or polar metabolites as variables for PCA of developing fibers. Auxin signaling, wall-loosening and lipid metabolism are highly active during fiber elongation, whereas cellulose biosynthesis is predominant and many other metabolic pathways are downregulated at the secondary cell wall synthesis stage. Transcript and metabolite profiles and enzyme activities are consistent in demonstrating a specialization process of cotton fiber development toward cellulose synthesis. These data demonstrate that cotton fiber cell at a certain stage has its own unique feature, and developmental stages of cotton fiber cells can be distinguished by their transcript and metabolite profiles. During the secondary cell wall synthesis stage, metabolic pathways are streamed into cellulose synthesis.