High Throughput SiRNA Screening for Chloropicrin and Hydrogen Fluoride-Induced Cornea Epithelial Cell Injury

Summary

High throughput small inhibitory RNA screening is an important tool that could help to more rapidly elucidate the molecular mechanisms of chemical cornea epithelial injury. Herein, we present the development and validation of exposure models and methods for the high throughput screening of hydrogen fluoride- and chloropicrin-induced cornea epithelial injury.

Abstract

Toxicant-induced ocular injury is a true ocular emergency because chemicals have the potential to rapidly inflict significant tissue damage. Treatments for toxicant-induced corneal injury are generally supportive as no specific therapeutics exist to treat these injuries. In the efforts to develop treatments and therapeutics to care for exposure, it can be important to understand the molecular and cellular mechanisms of these injuries. We propose that utilization of high throughput small inhibitory RNA (siRNA) screening can be an important tool that could help to more rapidly elucidate the molecular mechanisms of chemical cornea epithelial injury. siRNA are double stranded RNA molecules that are 19-25 nucleotides long and utilize the post-transcriptional gene silencing pathway to degrade mRNA which have homology to the siRNA. The resulting reduction of expression of the specific gene can then be studied in toxicant exposed cells to ascertain the function of that gene in the cellular response to the toxicant. The development and validation of in vitro exposure models and methods for the high throughput screening (HTS) of hydrogen fluoride- (HF) and chloropicrin- (CP) induced ocular injury are presented in this article. Although we selected these two toxicants, our methods are applicable to the study of other toxicants with minor modifications to the toxicant exposure protocol. The SV40 large T antigen immortalized human corneal epithelial cell line SV40-HCEC was selected for study. Cell viability and IL-8 production were selected as endpoints in the screening protocol. Several challenges associated with the development of toxicant exposure and cell culture methods suitable for HTS studies are presented. The establishment of HTS models for these toxicants allows for further studies to better understand the mechanism of injury and to screen for potential therapeutics for chemical ocular injury.

Introduction

Toxicant-induced ocular injury is a true ocular emergency because chemicals have the potential to rapidly inflict significant tissue damage. Unfortunately, treatments for toxicant-induced corneal injury are only generally supportive as no specific therapeutics exist to treat these injuries. The current treatment strategy is non-specific and primarily includes topical therapeutic treatments such as lubricants, antibiotics, and cycloplegics followed by anti-inflammatories (e.g., steroids) once the cornea has re-epithelialized^1,2. Despite the best current therapeutic treatment options available, long-ter....

Protocol

1. Cell Culture Maintenance

1. Grow the cell line SV40-HCEC at 37 °C, 5% CO₂, and 90% humidity in DMEM F-12 with 15% fetal bovine serum (FBS), 1% L-glutamine, 10 µg/L epidermal growth factor (EGF), and 5 mg/L insulin.
2. Passage the cell line every 3 to 4 days (depending on seeding density) to ensure that confluency never exceeds 80% during culture maintenance.
3. Detach the cells from flasks using a detachment solution (14 mL solution for every 150 cm² flask) and incubation at 37 °C for no more than 8 min.
4. Neutralize the detachment solution with an equal volume of cell culture medium and pellet the....

Results

Exposure Method Development

We refined and evaluated the suitability of the human corneal epithelial cell line SV40-HCEC for use in HTS studies. SV40-HCEC were immortalized using the SV-40 large T antigen and were a gift from Dhanajay Pal²³. There were too many variables explored in exposure methodology development to present concisely herein, and so, only some samples of findings we beli.......

Discussion

Herein we describe our methods and results on the development of a high throughput cornea epithelial cell screening model for the study of HF and CP injuries. We also present the results from the primary siRNA screen for HF injury. There were many challenges to the development of HTS models for the study of TIC injuries. Methods that we could find in the literature related to the study of HF, HFA or CP in cell culture models were of little help. Most in vitro studies on the fluoride ion involve oral cells and ut.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Bravo liquid handing platform	Agilent or equivalent	G5409A
Bravo plate shaker	Agilent or equivalent	Option 159
Bravo 96LT disposable tip head	Agilent or equivalent	Option 178	96-channel large tip pipetting head unit
Bravo 96ST disposable tip head	Agilent or equivalent	Option 177	96-channel small tip pipetting head unit
Bravo 384ST disposable tip head	Agilent or equivalent	Option 179	384-channel small tip pipetting head unit
Bravo 96 250 μL sterile barrier tips	Agilent or equivalent	19477-022
Bravo 384 30 μL sterile barrier tips	Agilent or equivalent	19133-212
Bravo 384 70 μL sterile barrier tips	Agilent or equivalent	19133-212
EnSpire multimode plate reader	Perkin Elmer or equivalent	2300-0000	AlphaLISA assay detector with high power laser excitation
IL-8 (human) AlphaLISA Detection Kit	Perkin Elmer or equivalent	AL224F	no-wash bead-based assay
ProxiPlate-384 Plus white 384-shallow well microplates	Perkin Elmer or equivalent	6008359
Lipofectamine RNAiMAX	Invitrogen or equivalent	13778500	Transfection reagent
Opti-MEM 1 Reduced Serum Medium	Invitrogen or equivalent	31985070
TrypLE Express	Gibco or equivalent	12605010	Cell detachment solution
IncuCyte Zoom	Essen Instruments or equivalent	ESSEN BIOSCI 4473	Incubator-housed automated microscope
Chloropicrin	Trinity Manufacturing or equivalent	N/A	Acute toxicity and irritant
DMEM-F12 cell culture medium	Invitrogen or equivalent	11330-057	Contains HEPES
Fetal bovine serum	Invitrogen or equivalent	1891471
Human epidermal growth factor (cell culture grade)	Invitrogen or equivalent	E9644-.2MG
Recombinant human insulin (cell culture grade)	Invitrogen or equivalent	12585-014
Penicillin-Streptomycin solution (cell culture grade)	Invitrogen or equivalent	15140122
Hydrocortisone (cell culture grade)	Sigma or equivalent	H0888-10G
Glucose  (cell culture grade)	Sigma or equivalent	G7021
PBS  (cell culture grade)	Sigma or equivalent	P5493
siRNA	Dharmacon or equivalent	various
Thiazolyl blue tetrazolium bromide	Sigma or equivalent	M5655	MTT assay substrate
siRNA buffer	Thermo or equivalent	B002000
96-well cell culture plates	Corning or equivalent	CLS3595
T150 cell culture flasks	Corning or equivalent	CLS430825
BSL-2 cell culture hood	Nuaire or equivalent	NU-540
300 mL robotic reservoirs	Thermo or equivalent	12-565-572
96 baffled automation reservoirs	Thermo or equivalent	1064-15-8
500 mL sterile disposable storage bottles	Corning or equivalent	CLS430282
Microplate heat sealer	Thermo or equivalent	AB-1443A
Microplate heat sealing foil	Thermo or equivalent	AB-0475
Cardamonin	Tocris or equivalent	2509	Anti-inflammatory, used as positive control
SKF 86002	Tocris or equivalent	2008	Anti-inflammatory, used as positive control
DMSO	Sigma or equivalent	D8418
48% hydrofluoric acid	Sigma or equivalent	339261	Corrosive and acute toxicity
1000 μL Single channel pipettors	Rainin or equivalent	17014382
200 μL Single channel pipettors	Rainin or equivalent	17014391
20 μL Single channel pipettors	Rainin or equivalent	17014392
1000 μL 12-channel pipettors	Rainin or equivalent	17014497
200 μL 12-channel pipettors	Rainin or equivalent	17013810
20 μL 12-channel pipettors	Rainin or equivalent	17013808
Pipettor tips 1000 μL	Rainin or equivalent	17002920
Pipettor tips 200 μL	Rainin or equivalent	17014294
Pipettor tips 20 μL	Rainin or equivalent	17002928
Chemical fume hood	Jamestown Metal Products	MHCO_229
384-well sample storage plates	Thermo or equivalent	262261
Sodium chloride	Sigma or equivalent	S6191
50 mL conical tubes	Thermo or equivalent	14-959-49A
Serological pipettes 50 mL	Corning or equivalent	07-200-576
Serological pipettes 25 mL	Corning or equivalent	07-200-575
Serological pipettes 10 mL	Corning or equivalent	07-200-574
Serological pipettes 5 mL	Corning or equivalent	07-200-573
SV40-HCEC immortalized human corneal epithelial cells	N/A	N/A	These cells are not commercially available, but can be obtained from the investigators cited in the article
Sceptor Handheld Automated Cell Counter	Millipore or equivalent	PHCC20060
GeneTitan Multi-Channel (MC) Instrument	Affymetrix or equivalent	00-0372
Affymetrix 24- and 96-array plates	Affymetrix or equivalent	901257; 901434
Draegger tube HF	Draeger or equivalent	8103251
Draegger tube CP	Draeger or equivalent	8103421
Draegger pump	Draeger or equivalent	6400000
Clear Plate seals	Resesarch Products International or Equivalent	202502
Reagent reservoirs	VistaLab Technologies or equivalent	3054-1000
Xlfit	IDBS or equivalent	N/A	Excel add-in used for automated curve fitting