Clinical Ophthalmology (Mar 2024)
Breaking-Down Barriers: Proposal of Using Cellulose Biosynthesis Inhibitors and Cellulase Enzyme as a Novel Treatment Modality for Vision Threatening Pythium Insidiosum Keratitis
Abstract
Bharat Gurnani,1 Radhika Natarajan,2 Madhuvanthi Mohan,2 Kirandeep Kaur3 1Department of Cataract, Cornea and Refractive Surgery, ASG Eye Hospital, Jodhpur, Rajasthan, 342008, India; 2Department of Cornea and Refractive Surgery, Sankara Nethralaya Medical Research Foundation, Chennai, Tamil Nadu, 600006, India; 3Department of Pediatric Ophthalmology and Strabismus, ASG Eye Hospital, Jodhpur, Rajasthan, 342008, IndiaCorrespondence: Bharat Gurnani, Department of Cornea and Refractive Surgery, ASG Eye Hospital, Jodhpur, Rajasthan, 342008, India, Tel +919080523059, Email [email protected]: Pythium insidiosum, an Oomycete, causes severe keratitis that endangers vision. Its clinical, morphological, and microbiological characteristics are often indistinguishable from those of fungal keratitis, earning it the moniker “parafungus”. Distinctive clinical hallmarks that set it apart from other forms of keratitis include radial keratoneuritis, tentacles, marginal infiltration, and a propensity for rapid limbal spread. The therapeutic approach to Pythium keratitis (PK) has long been a subject of debate, and topical and systemic antifungals and antibacterials have been tried with limited success. Approximately 80% of these eyes undergo therapeutic keratoplasty to salvage the eye. Hence, there is a need to innovate for alternative and better medical therapy to safeguard these eyes. The resistance of Pythium to standard antifungal treatments can be attributed to the absence of ergosterol in its cell wall. Cell walls of plants and algae have cellulose as an essential constituent. Cellulose imparts strength and structure and acts as the “skeleton” of the plant. Fungal and animal cell walls typically lack cellulose. The cellular architecture of Pythium shares a similarity with plant and algal cells through the incorporation of cellulose within its cell wall structure. Inhibitors targeting cellulose biosynthesis (CBI), such as Indaziflam, Isoxaben, and Quinoxyphen, serve as critical tools for elucidating the pathways of cellulose synthesis. Furthermore, the enzymatic action of cellulase is instrumental for the extraction of proteins and DNA. To circumvent this issue, we hypothesize that CBI’s and cellulase enzymes can act on the Pythium cell wall and may effectively treat PK. The available literature supporting the hypothesis and proof of concept has also been discussed. We have also discussed these drugs’ molecular mechanism of action on the Pythium cell wall. We also aim to propose how these drugs can be procured and used as a potential medical management option for this devastating entity.Keywords: Pythium insidiosum, keratitis, cellulose biosynthesis inhibitors, cellulase enzyme, antifungals
