Corneal Lymphatics: Role in Ocular Inflammation as Inducer and Responder of Adaptive Immunity

The normal cornea is devoid of lymphatic and blood vessels, thus suppressing both the afferent (lymphatic) and efferent (vascular) arms of the immune response–contributing to its ‘immune privilege’. Inflammation, however, negates this unique ‘immune’ and ‘angiogenic’ privilege of the cornea. Abnormal blood vessel growth from pre-existing limbal vessels into the cornea has been studied for many years, but it is only recently that the significance of new lymphatic vessels (lymphangiogenesis) in ocular inflammatory diseases has been demonstrated. Whereas blood vessels in inflamed ocular surface provide a route of entry for immune effector cells to the cornea, lymphatics facilitate the exit of antigen-presenting cells and antigenic material from the cornea to regional lymph nodes, thus promoting induction of adaptive immune response. This review summarizes the current evidence for lymphangiogenesis in the cornea, and describes its molecular mediators; and discusses the interface between corneal lymphangiogenesis and adaptive immunity. Furthermore, the pathophysiologic implications of corneal lymphangiogenesis in the setting of allo- and autoimmune-mediated corneal inflammation are discussed

Corneal Inflammation After Miniature Keratoprosthesis Implantation

Citation: Crnej A, Omoto M, Dohlman TH, Dohlman CH, Dana R. Corneal inflammation after miniature keratoprosthesis implantation. Invest Ophthalmol Vis Sci

Low-Cost and Readily Available Tissue Carriers for the Boston Keratoprosthesis: A Review of Possibilities

The Boston keratoprosthesis (B-KPro), currently the most commonly used artificial cornea worldwide, can provide rapid visual rehabilitation for eyes with severe corneal opacities not suitable for standard corneal transplantation. However, the B-KPro presently needs a corneal graft as a tissue carrier. Although corneal allograft tissue is readily available in the United States and other developed countries with established eye banks, the worldwide need vastly exceeds supply. Therefore, a simple, safe, and inexpensive alternative to corneal allografts is desirable for the developing world. We are currently exploring reasonable alternative options such as corneal autografts, xenografts, noncorneal autologous tissues, and laboratory-made tissue constructs, as well as modifications to corneal allografts, such as deep-freezing, glycerol-dehydration, gamma irradiation, and cross-linking. These alternative tissue carriers for the B-KPro are discussed with special regard to safety, practicality, and cost for the developing world

Signal Activation and Inactivation by the G Helical Domain: A Long-Neglected Partner in G Protein Signaling

Heterotrimeric guanine nucleotide–binding proteins (G proteins) are positioned at the top of many signal transduction pathways. The G protein α subunit is composed of two domains, one that resembles Ras and another that is composed entirely of α helices. Historically, most attention has focused on the Ras-like domain, but emerging evidence reveals that the helical domain is an active participant in G protein signaling

Dynamic Ubiquitination of the Mitogen-activated Protein Kinase Kinase (MAPKK) Ste7 Determines Mitogen-activated Protein Kinase (MAPK) Specificity

Ubiquitination is a post-translational modification that tags proteins for proteasomal degradation. In addition, there is a growing appreciation that ubiquitination can influence protein activity and localization. Ste7 is a prototype MAPKK in yeast that participates in both the pheromone signaling and nutrient deprivation/invasive growth pathways. We have shown previously that Ste7 is ubiquitinated upon pheromone stimulation. Here, we show that the Skp1/Cullin/F-box ubiquitin ligase SCFCdc4 and the ubiquitin protease Ubp3 regulate Ste7 ubiquitination and signal specificity. Using purified components, we demonstrate that SCFCdc4 ubiquitinates Ste7 directly. Using gene deletion mutants, we show that SCFCdc4 and Ubp3 have opposing effects on Ste7 ubiquitination. Although SCFCdc4 is necessary for proper activation of the pheromone MAPK Fus3, Ubp3 is needed to limit activation of the invasive growth MAPK Kss1. Finally, we show that Fus3 phosphorylates Ubp3 directly and that phosphorylation of Ubp3 is necessary to limit Kss1 activation. These results reveal a feedback loop wherein one MAPK limits the ubiquitination of an upstream MAPKK and thereby prevents spurious activation of a second competing MAPK

Reliable intraocular pressure measurement using automated radio-wave telemetry

Purpose To present an autonomous intraocular pressure (IOP) measurement technique using a wireless implantable transducer (WIT) and a motion sensor. Methods: The WIT optical aid was implanted within the ciliary sulcus of a normotensive rabbit eye after extracapsular clear lens extraction. An autonomous wireless data system (AWDS) comprising of a WIT and an external antenna aided by a motion sensor provided continuous IOP readings. The sensitivity of the technique was determined by the ability to detect IOP changes resulting from the administration of latanoprost 0.005% or dorzolamide 2%, while the reliability was determined by the agreement between baseline and vehicle (saline) IOP. Results: On average, 12 diurnal and 205 nocturnal IOP measurements were performed with latanoprost, and 26 diurnal and 205 nocturnal measurements with dorzolamide. No difference was found between mean baseline IOP (13.08±2.2 mmHg) and mean vehicle IOP (13.27±2.1 mmHg) (P=0.45), suggesting good measurement reliability. Both antiglaucoma medications caused significant IOP reduction compared to baseline; latanoprost reduced mean IOP by 10% (1.3±3.54 mmHg; P<0.001), and dorzolamide by 5% (0.62±2.22 mmHg; P<0.001). Use of latanoprost resulted in an overall twofold higher IOP reduction compared to dorzolamide (P<0.001). Repeatability was ±1.8 mmHg, assessed by the variability of consecutive IOP measurements performed in a short period of time (≤1 minute), during which the IOP is not expected to change. Conclusion: IOP measurements in conscious rabbits obtained without the need for human interactions using the AWDS are feasible and provide reproducible results

Reliable intraocular pressure measurement using automated radio-wave telemetry

Purpose To present an autonomous intraocular pressure (IOP) measurement technique using a wireless implantable transducer (WIT) and a motion sensor. Methods: The WIT optical aid was implanted within the ciliary sulcus of a normotensive rabbit eye after extracapsular clear lens extraction. An autonomous wireless data system (AWDS) comprising of a WIT and an external antenna aided by a motion sensor provided continuous IOP readings. The sensitivity of the technique was determined by the ability to detect IOP changes resulting from the administration of latanoprost 0.005% or dorzolamide 2%, while the reliability was determined by the agreement between baseline and vehicle (saline) IOP. Results: On average, 12 diurnal and 205 nocturnal IOP measurements were performed with latanoprost, and 26 diurnal and 205 nocturnal measurements with dorzolamide. No difference was found between mean baseline IOP (13.08±2.2 mmHg) and mean vehicle IOP (13.27±2.1 mmHg) (P=0.45), suggesting good measurement reliability. Both antiglaucoma medications caused significant IOP reduction compared to baseline; latanoprost reduced mean IOP by 10% (1.3±3.54 mmHg; P<0.001), and dorzolamide by 5% (0.62±2.22 mmHg; P<0.001). Use of latanoprost resulted in an overall twofold higher IOP reduction compared to dorzolamide (P<0.001). Repeatability was ±1.8 mmHg, assessed by the variability of consecutive IOP measurements performed in a short period of time (≤1 minute), during which the IOP is not expected to change. Conclusion: IOP measurements in conscious rabbits obtained without the need for human interactions using the AWDS are feasible and provide reproducible results

Challenges in acanthamoeba keratitis: a review

To review challenges in the diagnosis and management of Acanthamoeba keratitis (AK), along with prognostic factors, in order to help ophthalmologists avoid misdiagnosis, protracted treatment periods, and long-term negative sequelae, with an overarching goal of improving patient outcomes and quality of life, we examined AK studies published between January 1998 and December 2019. All manuscripts describing clinical manifestations, diagnosis, treatment, prognosis, and challenges in short- and long-term management were included. The diagnosis of AK is often challenging. An increased time between symptom onset and the initiation of appropriate therapy is associated with poorer visual outcomes. The timely initiation of standardized antiamoebic therapies improves visual outcomes, decreases the duration of treatment, and reduces the chances of needing surgical intervention. In clinical practice, AK diagnosis is often missed or delayed, leading to poorer final visual outcomes and a negative impact on patient morbidity and quality of life

Regulation of Yeast G Protein Signaling by the Kinases That Activate the AMPK Homolog Snf1

Extracellular signals, such as nutrients and hormones, cue intracellular pathways to produce adaptive responses. Often, cells must coordinate their responses to multiple signals to produce an appropriate outcome. We showed that components of a glucose-sensing pathway acted on components of a heterotrimeric guanine nucleotide–binding protein (G protein)–mediated pheromone signaling pathway in the yeast Saccharomyces cerevisiae. We demonstrated that the G protein α subunit Gpa1 was phosphorylated in response to conditions of reduced glucose availability and that this phosphorylation event contributed to reduced pheromone-dependent stimulation of mitogen-activated protein kinases, gene transcription, cell morphogenesis, and mating efficiency. We found that Elm1, Sak1, and Tos3, the kinases that phosphorylate Snf1, the yeast homolog of adenosine monophosphate–activated protein kinase (AMPK), in response to limited glucose availability, also phosphorylated Gpa1 and contributed to the diminished mating response. Reg1, the regulatory subunit of the phosphatase PP1 that acts on Snf1, was likewise required to reverse the phosphorylation of Gpa1 and to maintain the mating response. Thus, the same kinases and phosphatase that regulate Snf1 also regulate Gpa1. More broadly, these results indicate that the pheromone signaling and glucose-sensing pathways communicate directly to coordinate cell behavior

Effect of Penetrating Keratoplasty and Keratoprosthesis Implantation on the Posterior Segment of the Eye

Purpose To compare the effects of post-penetrating keratoplasty (PK) and post-keratoprosthesis (KPro) surgery-related inflammation on the posterior segment of the eye and to assess inhibition of tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β) on these effects. Methods: BALB/C (syngeneic) or C57BL/6 (allogeneic) corneas were transplanted onto BALB/C host beds as part of PK or miniature KPro (m-KPro) implantation. Intraocular pressure (IOP) was measured via an intracameral pressure sensor; tissues were harvested and analyzed 8 weeks after surgery. Expression of TNFα and IL-1β in the retina was analyzed using real-time quantitative (q)PCR. Optic nerve degeneration (axon count, circularity, and area) was assessed quantitatively using ImageJ software. After m-KPro implantation, mice were treated with saline, anti-TNFα, or anti-IL-1β antibody, and axonal loss was assessed after 10 weeks. Results: Mean IOP was within normal limits in the operated and fellow eyes in all groups. The mRNA expression of TNFα and IL-1β was highest in m-KPro groups with either syngeneic or an allogeneic carrier. We observed optic nerve degeneration in both allogeneic PK and m-KPro implanted eyes with an allogeneic carrier. However, TNFα blockade significantly reduced axonal loss by 35%. Conclusions: Allogeneic PK and m-KPro implants with an allogeneic carrier lead to chronic inflammation in the posterior segment of the eye, resulting in optic nerve degeneration. In addition, blockade of TNFα prevents axonal degeneration in this preclinical model of allogeneic m-KPro (alloKPro) implantation