J Korean Ophthalmol Soc.  2012 May;53(5):700-706.

Suppression of VEGF and Decrease in Vascular Leakage by Pyridoxal 5'-Phosphate in Diabetic Rats

• Hong IH
• Yu HG
• Park SP

Abstract

PURPOSE
The authors of the present study investigated whether pyridoxal 5'-phosphate (PLP), an active coenzyme of vitamin B6, could inhibit the development of diabetic retinopathy in streptozotocin (STZ)-induced diabetic rats.
METHODS
Seven-week-old Spraque-Dawley rats (n = 20) were used in the present study. STZ (70 mg/kg) was injected intraperitoneally to induce diabetes. Blood glucose and body weight were monitored. Intraperitoneal injections of 5 microg and 50 microg PLP were administered every two days from the second week of induced diabetes. During the third week of PLP injections, the concentration level of plasma homocysteine was measured. In addition, functional status was examined by vitreous fluorophotometer and anatomical status by vascular endothelial growth factor (VEGF) staining in the retina.
RESULTS
Based on vitreous fluorophotometry examination, the PLP injection group proved to have a lower level of fluorescein concentration in the vitreous. Additionally, immunohistochemical staining revealed down-regulation of VEGF expression in the PLP group. In addition, the PLP group had a lower plasma homocysteine concentration. However, an over-dosage injection of PLP did not appear to have any noticeable impact on the treatment of diabetes.
CONCLUSIONS
PLP, an active coenzyme of vitamin B6, proved to have inhibitory effects on VEGF expression and vascular leakage in the diabetic rat retina.

Keyword

Diabetic retinopathy; Pyridoxal 5'-phosphate (PLP); Vascular endothelial growth factor (VEGF); Vitreous fluorophotometry

MeSH Terms

Animals
Blood Glucose
Body Weight
Diabetic Retinopathy
Down-Regulation
Fluorescein
Fluorophotometry
Homocysteine
Injections, Intraperitoneal
Plasma
Pyridoxal
Rats
Retina
Streptozocin
Vascular Endothelial Growth Factor A
Vitamin B 6
Blood Glucose
Fluorescein
Homocysteine
Pyridoxal
Streptozocin
Vascular Endothelial Growth Factor A
Vitamin B 6

Figure

• 

  Figure 1 Normal and high dose pyridoxal 5'-phosphate-treated group shows no significant decrease in the blood glucose level compared to placebo-treated group (p > 0.05, chi-square test). DM = diabetes mellitus; PLP = pyridoxal 5'-phosphate.

• 

  Figure 2 Normal and high dose pyridoxal 5'-phosphate-treated group shows poor body weight gain compared to the normal control and showed no difference compared to placebo-treated group(p > 0.05, chi-square test). DM = diabetes mellitus; PLP = pyridoxal 5'-phosphate.

• 

  Figure 3 Normal and high dose pyridoxal 5'-phosphate-treated group shows lower blood homocysteine level than that of the placebo-treated group (Mann-Whitney U test). DM = diabetes mellitus; PLP = pyridoxal 5'-phosphate.

• 

  Figure 4 Fluorophotometry shows less leakage of the fluorescein from the retinal vessels in normal and high dose pyridoxal 5'-phosphate-treated group than placebo-treated group. However, pyridoxal 5'-phosphate-treated group shows more leakage compared to the normal control (Mann-Whitney U test). DM = diabetes mellitus; PLP = pyridoxal 5'-phosphate.

• 

  Figure 5 VEGF increased much more in the retina of the control group than in the normal and high dose pyridoxal 5'-phosphate-treated group. DM = diabetes mellitus; PLP = pyridoxal 5'-phosphate.

Reference

1. Amos AF, McCarthy DJ, Zimmet P. The rising global burden of diabetes and its complications: estimates and projections to the year 2010. Diabet Med. 1997. 14:Suppl 5. S1–S85.

2. Marshall SM, Flyvbjerg A. Prevention and early detection of vascular complications of diabetes. BMJ. 2006. 333:475–480.

3. Curtis TM, Gardiner TA, Stitt AW. Microvascular lesions of diabetic retinopathy: clues towards understanding pathogenesis? Eye (Lond). 2009. 23:1496–1508.

4. Nishikawa T, Edelstein D, Du XL, et al. Normalizing mitochondrial superoxide production blocks three pathways of hyperglycaemic damage. Nature. 2000. 404:787–790.

5. Brownlee M. Biochemistry and molecular cell biology of diabetic complications. Nature. 2001. 414:813–820.

6. Van Hecke MV, Dekker JM, Nijpels G, et al. Inflammation and endothelial dysfunction are associated with retinopathy: the Hoorn Study. Diabetologia. 2005. 48:1300–1306.

7. Schram MT, Chaturvedi N, Schalkwijk CG, et al. Markers of inflammation are cross-sectionally associated with microvascular complications and cardiovascular disease in type 1 diabetes-- the EURODIAB Prospective Complications Study. Diabetologia. 2005. 48:370–378.

8. Brazionis L, Rowley K Sr, Itsiopoulos C, et al. Homocysteine and diabetic retinopathy. Diabetes Care. 2008. 31:50–56.

9. UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet. 1998. 352:837–853.

10. Yamagishi S, Matsui T, Nakamura K, et al. Pigment-epithelium-derived factor suppresses expression of receptor for advanced glycation end products in the eye of diabetic rats. Ophthalmic Res. 2007. 39:92–97.

11. Kowluru RA, Odenbach S. Effect of long-term administration of alpha-lipoic acid on retinal capillary cell death and the development of retinopathy in diabetic rats. Diabetes. 2004. 53:3233–3238.

12. Bursell SE, Clermont AC, Aiello LP, et al. High-dose vitamin E supplementation normalizes retinal blood flow and creatinine clearance in patients with type 1 diabetes. Diabetes Care. 1999. 22:1245–1251.

13. Kim ES, Yu SY, Kwon SJ, et al. Clinical evaluation of patients with monproliferative diabetic retinopathy following medication of anthocyanoside: multicenter study. J Korean Ophthalmol Soc. 2008. 49:1629–1633.

14. Yu SI, Jung HJ, Her DY, et al. Suppression of VEGF and STAT3 by lipoic acid in experimental diabetic rat retina. J Korean Ophthalmol Soc. 2007. 48:715–724.

15. Okada M, Shibuya M, Yamamoto E, Murakami Y. Effect of diabetes on vitamin B6 requirement in experimental animals. Diabetes Obes Metab. 1999. 1:221–225.

16. Toyota T, Kai Y, Kakizaki M, et al. The endocrine pancreas in pyridoxine deficient rats. Tohoku J Exp Med. 1981. 134:331–336.

17. Araki A. Homocysteine and diabetic macroangiopathy. Nihon Rinsho. 2006. 64:2153–2158.

18. Cunha-Vaz JG, Gray JR, Zeimer RC, et al. Characterization of the early stages of diabetic retinopathy by vitreous fluorophotometry. Diabetes. 1985. 34:53–59.

19. Van Schaik HJ, Benitez del Castillo JM, Caubergh MJ, et al. Evaluation of diabetic retinopathy by fluorophotometry. european concerted action on ocular fluorometry. Int Ophthalmol. 1998-1999. 22:97–104.

20. Do carmo A, Ramos P, Reis A, et al. Breakdown of the inner and outer blood retinal barrier in streptozotocin-induced diabetes. Exp Eye Res. 1998. 67:569–575.

21. Anis HH, Bahgat M, Peyman GA, et al. Effect of pyridoxine on the blood-retina barrier in experimentally induced hyperglycemia in rats. Can J Ophthalmol. 1991. 26:354–357.

22. Castro R, Rivera I, Blom HJ, et al. Homocysteine metabolism, hyperhomocysteinaemia and vascular disease: an overview. J Inherit Metab Dis. 2006. 29:3–20.

23. Lominadze D, Roberts AM, Tyagi N, et al. Homocysteine causes cerebrovascular leakage in mice. Am J Physiol Heart Circ Physiol. 2006. 290:H1206–H1213.

24. Moshal KS, Sen U, Tyagi N, et al. Regulation of homocysteine-induced MMP-9 by ERK1/2 pathway. Am J Physiol Cell Physiol. 2006. 290:C883–C891.

25. Aydemir O, Turkcuoglu P, Guler M, et al. Plasma and vitreous homocysteine concentrations in patients with proliferative diabetic retinopathy. Retina. 2008. 28:741–743.

26. Brazionis L, Rowley K Sr, Itsiopoulos C, et al. Homocysteine and diabetic retinopathy. Diabetes Care. 2008. 31:50–56.

27. Adamis AP, Miller JW, Bernal MT, et al. Increased vascular endothelial growth factor levels in the vitreous of eyes with proliferative diabetic retinopathy. Am J Ophthalmol. 1994. 118:445–450.

28. Aiello LP, Avery RL, Arrigg PG, et al. Vascular endothelial growth factor in ocular fluid of patients with diabetic retinopathy and other retinal disorders. N Engl J Med. 1994. 331:1480–1487.

29. Mathews MK, Merges C, McLeod DS, Lutty GA. Vascular endothelial growth factor and vascular permeability changes in human diabetic retinopathy. Invest Ophthalmol Vis Sci. 1997. 38:2729–2741.

30. Higuchi O, Nakagawa K, Tsuzuki T, et al. Aminophospholipid glycation and its inhibitor screening system: a new role of pyridoxal 5'-phosphate as the inhibitor. J Lipid Res. 2006. 47:964–974.

31. Padayatti PS, Jiang C, Glomb MA, et al. High concentrations of glucose induce synthesis of argpyrimidine in retinal endothelial cells. Curr Eye Res. 2001. 23:106–115.

32. Canning P, Glenn JV, Hsu DK, et al. Inhibition of advanced glycation and absence of galectin-3 prevent blood-retinal barrier dysfunction during short-term diabetes. Exp Diabetes Res. 2007. 2007:51837.

33. Moore TC, Moore JE, Kaji Y, et al. The role of advanced glycation end products in retinal microvascular leukostasis. Invest Ophthalmol Vis Sci. 2003. 44:4457–4464.

34. Kiran SG, Dorisetty RK, Umrani MR, et al. Pyridoxal 5' phosphate protects islets against streptozotocin-induced beta-cell dysfunction--in vitro and in vivo. Exp Biol Med (Maywood). 2011. 236:456–465.

35. Chen BH, Jiang DY, Tang LS. Advanced glycation end-products induce apoptosis involving the signaling pathways of oxidative stress in bovine retinal pericytes. Life Sci. 2006. 79:1040–1048.

36. Yamagishi S, Fujimori H, Yonekura H, et al. Advanced glycation endproducts accelerate calcification in microvascular pericytes. Biochem Biophys Res Commun. 1999. 258:353–357.

37. Stitt A, Gardiner TA, Alderson NL, et al. The AGE inhibitor pyridoxamine inhibits development of retinopathy in experimental diabetes. Diabetes. 2002. 51:2826–2832.