Investigation into the usefulness of cynomolgus monkeys with spontaneously elevated intraocular pressure as a model for glaucoma treatment research

Many glaucoma treatments focus on lowering intraocular pressure (IOP), with novel drugs continuing to be developed. One widely used model involves raising IOP by applying a laser to the trabecular iris angle (TIA) of cynomolgus monkeys to damage the trabecular meshwork. This model, however, presents challenges such as varying IOP values, potential trabecular meshwork damage, and risk of animal distress. This study investigated whether animals with naturally high IOP (>25 mmHg) could be used to effectively evaluate IOP-lowering drugs, thereby possibly replacing laser-induced models. Relationships between TIA size, IOP, and pupil diameter were also examined. Three representative IOP-lowering drugs (latanoprost, timolol, ripasudil) were administered, followed by multiple IOP measurements and assessment of corneal thickness, TIA, and pupil diameter via anterior segment optical coherence tomography (AS-OCT). There was a positive correlation was noted between IOP and corneal thickness before instillation, and a negative correlation between IOP and TIA before instillation. Our findings suggest animals with naturally high IOP could be beneficial for glaucoma research and development as a viable replacement for the laser-induced model and that measuring TIA using AS-OCT along with IOP yields a more detailed evaluation.

Delphinidins from Maqui Berry (Aristotelia chilensis) ameliorate the subcellular organelle damage induced by blue light exposure in murine photoreceptor-derived cells

BACKGROUND

Blue light exposure is known to induce reactive oxygen species (ROS) production and increased endoplasmic reticulum stress, leading to apoptosis of photoreceptors. Maqui berry (Aristotelia chilensis) is a fruit enriched in anthocyanins, known for beneficial biological activities such as antioxidation. In this study, we investigated the effects of Maqui berry extract (MBE) and its constituents on the subcellular damage induced by blue light irradiation in mouse retina-derived 661W cells.

METHODS

We evaluated the effects of MBE and its main delphinidins, delphinidin 3-O-sambubioside-5-O-glucoside (D3S5G) and delphinidin 3,5-O-diglucoside (D3G5G), on blue light-induced damage on retinal cell line 661W cells. We investigated cell death, the production of ROS, and changes in organelle morphology using fluorescence microscopy. The signaling pathway linked to stress response was evaluated by immunoblotting in the whole cell lysates or nuclear fractions. We also examined the effects of MBE and delphinidins against rotenone-induced mitochondrial dysfunction.

RESULTS

Blue light-induced cell death, increased intracellular ROS generation and mitochondrial fragmentation, decreased ATP-production coupled respiration, caused lysosomal membrane permeabilization, and increased ATF4 protein level. Treatment with MBE and its main constituents, delphinidin 3-O-sambubioside-5-O-glucoside and delphinidin 3,5-O-diglucoside, prevented these defects. Furthermore, MBE and delphinidins also protected 661W cells from rotenone-induced cell death.

CONCLUSIONS

Maqui berry may be a useful protective agent for photoreceptors against the oxidative damage induced by exposure to blue light.

Creation of Retinal Vein Occlusion Model in Cynomolgus Monkeys and Determination of its Pathological Features

OBJECTIVE

A retinal vein occlusion (RVO) is a relatively common retinal vascular disorder, especially in the elderly. Many experiments have been performed on patients with an RVO but performing any type of experiments and especially longitudinal experiments on humans is difficult, if not impossible, on ethical grounds. Therefore, we have created a retinal vein occlusion (RVO) model by laser irradiation of cynomolgus monkeys after intravenous injection of rose bengal. We evaluated the pathological changes of the retina, and the effects of ranibizumab, an anti-vascular endothelial growth factor (VEGF) antibody, on the characteristics of the RVO.

METHODS

The integrity of the vascular system was evaluated by fluorescein angiography (FA), and the retinal thickness and volume were determined by optical coherence tomography (OCT). The cytokines and growth factors in the aqueous humour were identified by multiplex profiling.

RESULTS

Our results showed that ranibizumab decreased the degree of vascular leakage and retinal edema at 1-3 days (acute phase) and 3-7 days (subacute phase), and suppressed foveal thinning at 28-42 days (chronic phase) after the laser irradiation. Ranibizumab also decreased the area of the foveal avascular zone, and the area was negatively and significantly correlated with the thickness of the ganglion cell layer (GCL) complex. Furthermore, ranibizumab reduced the increased expression of VEGF in the aqueous humor, but did not affect the expressions of interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), angiopoietin-1 (ANG-1), or angiopoietin-2 (ANG-2). These findings suggest that ranibizumab attenuates the retinal edema and subsequent retinal atrophy in part by neutralizing VEGF. However, other cytokines and growth factors were also affected by the ranibizumab, which suggests that not only VEGF but also other unidentified agents might play a role in the pathogenesis of the RVO.

CONCLUSION

We have created a non-human primate RVO model, which resembles the clinical RVO pathology. In this model, an injection of ranibizumab leads to a reduction in vascular leakage and the retinal thickness and volume by blocking the expression of VEGF. Our model might be useful for investigating the pathological mechanisms of RVOs and explore new therapeutic agents for RVO.

Free-Radical Scavenger NSP-116 Protects the Corneal Epithelium against UV-A and Blue LED Light Exposure

The corneal epithelium is continuously exposed to oxygen, light, and environmental substances. Excessive exposure to those stresses is thought to be a risk factor for eye diseases. Photokeratitis is damage to the corneal epithelium resulting in a painful eye condition caused by unprotected exposure to UV rays, usually from sunlight, and is often found in people who spend a long time outdoors. In modern life, human eyes are exposed to artificial light from light-emitting diode (LED) displays of computers and smartphones, and it has been shown that short-wavelength (blue) LED light can damage eyes, especially photoreceptors. However, the effect of blue LED light on the cornea is less understood. In addition, it is important to develop new treatments for preserving human eyesight and eye health from light stress. Here, we used human corneal epithelial cells-transformed (HCE-T) cells as an in-vitro model to investigate the protective effect of NSP-116, an imidazolyl aniline derivative, against the oxidative stress induced by light in the corneal epithelium. Treatment with 10 µM NSP-116 significantly increased the cell viability and reduced the death ratio following UV or blue LED light exposure. Furthermore, NSP-116 treatment decreased light-induced reactive oxygen species production and preserved the mitochondrial membrane potential. Immunoblotting data showed that NSP-116 suppressed the stress response pathway. Finally, NSP-116 treatment prevented corneal epithelial apoptosis induced by blue LED light in an in-vivo mouse model. In conclusion, NSP-116 has a protective effect against oxidative stress and corneal cell death from both UV and blue LED light exposure.

Anti-vascular Endothelial Growth Factor Antibody Limits the Vascular Leakage and Decreases Subretinal Fibrosis in a Cynomolgus Monkey Choroidal Neovascularization Model

OBJECTIVE

This study was conducted to evaluate the effects of anti-vascular endothelial growth factor (VEGF) antibody (bevacizumab) on vascular leakage and fibrosis in a monkey choroidal neovascularization (CNV) model. The relationship between fibrotic tissue and subretinal hyper-reflective material (SHRM), in optical coherence tomography (OCT) images, was also investigated.

METHODS

Experimental CNV was induced in male cynomolgus monkeys by laser photocoagulation. Intravitreal injection of bevacizumab at 0.5 mg/eye/dosing was initiated 2 weeks before or after laser irradiation and thereafter, conducted intermittently at 2- or 3-week intervals. Fluorescein fundus angiography (FA) and OCT imaging were conducted weekly from 2 to 7 weeks after laser irradiation. CNV leakage was evaluated by an established grading method using FA images. To assess the fibrosis and scarring, Masson's trichrome specimens of each CNV lesion were prepared, and morphometric analysis was conducted using an image analysis software.

RESULTS

The effects of bevacizumab on vascular leakage were shown using an established evaluation method. Morphometric analysis of Masson's trichrome-stained (MT) specimens revealed that collagen fiber synthesis was suppressed by bevacizumab pre-treatment (-29.2%) or post-treatment (-19.2%). SHRM was detected in OCT images in a monkey CNV model, and a significant correlation between the SHRM area in the OCT images and the collagen fiber area in the MT specimens was noted.

CONCLUSION

In the established cynomolgus monkey CNV model, bevacizumab prevented blood leakage but could not completely suppress fibrosis. SHRM in the OCT images reflected retinal fibrous tissue in a laser-induced CNV monkey model. This model might be useful for elucidating the pathology and development therapy for neovascularization or fibrosis.

Genetic variants of UDP-glucuronosyltransferases 1A1, 1A6, and 1A9 in cynomolgus and rhesus macaques

1. In the cynomolgus macaque, UDP-glucuronosyltransferases (UGTs) 1As have similar molecular and enzymatic characteristics to those of their human orthologs. However, genetic polymorphisms in major cynomolgus UGT1A1/6/9 have not been investigated. 2. We re-sequenced UGT1A1, UGT1A6, and UGT1A9 in 186 cynomolgus macaques (bred in Cambodia, China, or Indonesia) and 54 rhesus macaques and found 15, 13, and 26 non-synonymous variants, respectively. 3. Of these UGT1A1, UGT1A6, and UGT1A9 variants, respectively, 10, 9, and 12 were unique to cynomolgus macaques; 4, 1, and 2 were unique to rhesus macaques; and 1, 2, and 5 were found in both cynomolgus and rhesus macaques. The frequency of the UGT1A1 mutation G69R was 23%, 28%, and 63% in cynomolgus macaques bred in Cambodia, China, and Indonesia, respectively, and 97% in rhesus macaques. 4. The O-glucuronidation activities of liver microsomes from cynomolgus and rhesus macaques with respect to estradiol, serotonin, and propofol were measured. Among these activities, liver microsomes from cynomolgus macaques heterozygous for UGT1A1 G69R (n = 11) showed significantly reduced estradiol 3-O-glucuronidation activities compared with those from wild-type animals (n = 38). 5. These results suggest genetic variants such as UGT1A1 G69R could influence the UGT1A1-mediated glucuronidation of drugs in cynomolgus and rhesus macaques.

Blue light-emitting diode irradiation promotes transcription factor EB-mediated lysosome biogenesis and lysosomal cell death in murine photoreceptor-derived cells

Exposure to blue light from light-emitting diodes (LEDs) is a source of damage for human eyes in today's modern life. Although it is well known that blue light can cause cellular damage and death, the molecular mechanism underlying this is still not fully understood. Here, we demonstrated that exposure to blue LED light increased lysosome levels and perinuclear cluster formation in 661W murine photoreceptor-derived cells. Irradiation with blue LED light promoted the nuclear transport of transcription factor EB (TFEB) and a subsequent increase in lysosomal-related gene expression. Moreover, blue LED light induced morphological changes in lysosomal structure and lysosomal membrane permeabilization (LMP). These effects were suppressed by an antioxidant, N-acetylcysteine (NAC). Finally, a calcium ion chelator, BAPTA-AM, attenuated blue LED light-induced lysosomal biogenesis and cell death. Taken together, these findings suggest that oxidative stress under blue LED light increases lysosome levels via the TFEB pathway in a calcium-dependent manner, resulting in the accumulation of damaged lysosomes and subsequently lysosomal cell death. Our results imply that lysosomal homeostasis plays a key role in the maintenance of eye function and the progression of retinal diseases.

[Muscle mass measurement by DXA and MRI in non-human primates]

The global population is aging rapidly and, in Japan, the number of elderly has been steadily rising. It is important to shrink the gap between the average lifespan and the number of years people can expect to remain healthy. This links with improving the quality of life for the elderly and reducing social welfare spending. Maintaining motor function is believed to be a key to extending the number of years a person remains healthy, but recent years have seen a rise in locomotive syndrome. Decreases in muscle mass with age, and the deterioration in motor functions leads to sarcopenia. However, there is a dearth of medicines for increasing muscle mass or muscular strength. In this study, we used non-human primates (NHPs), which have similar anatomical features to humans and have advanced functional differentiation between the fore- and hindlimbs, to examine a highly accurate method of measuring muscle mass using Magnetic Resonance Imaging (MRI) and compared it to Dual Energy X-ray Absorptiometry (DXA) usually used in clinical settings. The results showed that both MRI and DXA provided high repeatability. Furthermore, correlation analysis between the amount of excised muscle for measurement and the results from MRI and DXA showed a high correlation at all sites examined, with the correlation coefficient higher for MRI than for DXA. We expect that the establishment of a highly accurate method for measurement of muscle mass using MRI and DXA will give impetus to the development of drugs that target muscle mass.

Development in the cynomolgus macaque following administration of ustekinumab, a human anti-IL-12/23p40 monoclonal antibody, during pregnancy and lactation

BACKGROUND

Ustekinumab is a human monoclonal antibody that binds to the p40 subunit of interleukin (IL) 12 and IL-23 and inhibits their pharmacological activity. To evaluate potential effects of ustekinumab treatment during pregnancy, developmental studies were conducted in cynomolgus macaques.

METHODS

Ustekinumab was tested in two embryo/fetal development (EFD) studies and in a combined EFD/pre and postnatal development (PPND) study. In the EFD studies, pregnant macaques (12/group) were dosed with saline or ustekinumab (9 mg/kg IV, 22.5 mg/kg SC, or 45 mg/kg IV or SC during the period of major organogenesis, gestation day [GD] 20-50). Fetuses were harvested on GD100-102 and examined for any effects on development. In the EFD/PPND study, pregnant macaques were injected with saline or ustekinumab (22.5 or 45 mg/kg SC) from GD20 through lactation day 33. Infants were examined from birth through 6 months of age for morphological and functional development. Potential effects on the immune system were evaluated by immunophenotyping of peripheral blood lymphocytes and immunohistopathology of lymphoid tissues in fetuses and infants and by T-dependent antibody response (TDAR) to KLH and TTX and by DTH response in infants. Ustekinumab concentrations were measured in serum from dams, fetus, and infants and in breast milk.

RESULTS

Ustekinumab treatment produced no maternal toxicity and no toxicity in the fetuses or infants, including no effects on the TDAR or DTH responses. Ustekinumab was present in serum from GD100 fetuses and was present in infant serum through day 120 post-birth. Low levels of ustekinumab were present in breast milk.

CONCLUSIONS

Exposure of macaque fetuses and infants to ustekinumab had no adverse effects on pre- and postnatal development.

Left ventricular volume and function in cynomolgus monkeys using real-time three-dimensional echocardiography

BACKGROUND

The purpose of this study was to investigate the feasibility of evaluating cardiac function by real time three-dimensional (RT3D) echocardiography in isoflurane-anesthetized male cynomolgus monkeys. Additionally differences between inhibitory effects of beta-blockers and a Ca channel blocker on left ventricular (LV) function were examined.

METHODS AND RESULTS

End-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) in the control (without any drug effect) were not significantly changed by repetitive measurement at a 30-day interval. Propranolol and metoprolol (0.1 and 0.3 mg/kg/10 minutes, i.v.) caused a dose-dependent increase in ESV, but little effect on EDV, resulting in a decrease in EF. Verapamil (0.1 and 0.3 mg/kg/10 minutes, i.v.) increased both EDV and ESV, but decreased EF was noted at 0.3 mg/kg.

CONCLUSIONS

These results demonstrate the feasibility of RT3D echocardiography in providing reproducible estimations of LV volume and EF in monkeys when evaluating drugs that may affect cardiac function.

Evaluation of cardiac function in primates using real-time three-dimensional echocardiography as applications to safety assessment

INTRODUCTION

A timed non-invasive determination of cardiac function is potentially important for safety pharmacology and toxicity studies. The objectives of this study were to evaluate the accuracy of real-time three-dimensional (RT3D) echocardiography measurements of the left ventricular (LV) volume and LV function and to investigate the effects of some drugs on LV function in cynomolgus monkeys.

METHODS

RT3D echocardiography was performed (SONOS 7500, Philips Med Sys) under isoflurane inhalation. RT3D echocardiography measurements and reconstructions were obtained using Tom-Tec (4DLV analysis). We determined end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), stroke volume (SV), cardiac output (CO) and heart rate as assessments of LV function. EDV, calculated from two-dimensional (2D) echocardiography and RT3D echocardiography, and the actual LV volume were evaluated and compared. Furthermore, each parameter was determined before and after intravenous infusion (5 or 10 min) of propranolol, verapamil and dobutamine.

RESULTS

A strong correlation was found between the actual LV volume and that calculated from RT3D echocardiography (r=0.96, p<0.001). Propranolol (0.1 mg/kg/10 min, n=5) caused an increase in ESV, but not EDV, resulting in a decrease in EF and SV, while verapamil produced increases in both EDV and ESV. Dobutamine (0.01 mg/kg/5 min, n=5) produced decreases in both EDV and ESV and thereby the increased CO resulted from the increased SV.

DISCUSSION

These results demonstrate that RT3D echocardiography provides a feasible and accurate estimation of LV volume and EF for safety pharmacology and toxicity studies.

In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects tooth development in rhesus monkeys

We thought to validate the current tolerable daily intake (TDI) value for dioxin (4 pg/kg) in Japan. Pregnant rhesus monkeys received an initial dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 0, 30, or 300 ng/kg subcutaneously) on day 20 of gestation; the dams received additional injection of 5% of the initial dose every 30 days until day 90 after delivery. The teeth of stillborn, postnatally dead, and surviving offspring (now approximately 4 years old) were evaluated. None of the offspring in the 0 and 30 ng/kg groups (n=17 and 15, respectively) had tooth abnormalities, whereas 10 of 17 in the 300 ng/kg had them. These findings suggest the lowest-observed adverse-effect level (LOAEL) for TCDD in the rhesus monkey is between 30 and 300 ng/kg, and probably is close to that for rodents (86 ng/kg) on which the current TDI was based. It is reasonable to conclude that the current TDI needs no immediate modification.

Effect of repeated administrations of neomycin on the neuromuscular functions and the enhancement of d-tubocurarine action in mice

Effects of repeated s.c. treatments with 50 mumol (approx. 31 mg)/kg/day of neomycin for 10 or 15 days were examined in mice. There were no significant differences between saline and neomycin treatment groups in the motor coordination assessed by rota-rod test and traction test. On tension recordings, an in vitro addition of d-tubocurarine inhibited the twitch tensions evoked by the nerve stimulations in both cases of saline or neomycin treatment. Neomycin treatments shifted the concentration-response curve between twitch tension and d-tubocurarine to the left, dependently on its injection days. These results suggest that repeated treatments with neomycin enhance the inhibitory effect of d-tubocurarine on the neuromuscular transmission in mice without eliciting motor incoordination and muscle relaxation.