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Histamine metabolism influences blood vessel branching in zebrafish reg6 mutants.

Huang CC, Huang CW, Cheng YS, Yu J - BMC Dev. Biol. (2008)

Bottom Line: Interestingly, when reg6 adults that had already developed swollen vessel lumina in regenerating fins were treated with histamine or SKF91488, either treatment significantly reduced the number of swollen vessels within 12 h, suggesting a rapid and constant influence of histamine on blood vessel branching.Finally, we identified that the transcription factor, egr-1 (early growth response factor 1), was closely associated with the reg6 phenotype and chemical treatments.Taken together, our results suggest that blood vessel branching is influenced by histamine metabolism, possibly through regulating the expression of the egr-1 transcription factor.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. huangcc@gate.sinica.edu.tw

ABSTRACT

Background: Vascular branching morphogenesis is responsible for the extension of blood vessels into growing tissues, a process crucial for organogenesis. However, the genetic mechanism for vessel branching is largely unknown. Zebrafish reg6 is a temperature-sensitive mutation exhibiting defects in blood vessel branching which results in the formation of swollen vessel lumina during capillary plexus formation.

Results: We performed a screening for chemical suppressors of reg6 and identified SKF91488, an inhibitor of histamine methyltransferase (HMT), that can rescue the reg6 vessel branching defects in a dose-dependent manner. Inhibition of HMT by SKF91488 presumably blocks histamine degradation, thus causing histamine accumulation. Consistent with this idea, we found that a high level of histamine also showed significant suppression of reg6 vessel phenotypes. Interestingly, when reg6 adults that had already developed swollen vessel lumina in regenerating fins were treated with histamine or SKF91488, either treatment significantly reduced the number of swollen vessels within 12 h, suggesting a rapid and constant influence of histamine on blood vessel branching. Furthermore, the expression of HMT was significantly elevated in reg6 regenerating fins. Conversely, lowering histamine by administering urocanic acid, a histidine decarboxylase inhibitor, enhanced the reg6 phenotypes. Finally, we identified that the transcription factor, egr-1 (early growth response factor 1), was closely associated with the reg6 phenotype and chemical treatments.

Conclusion: Taken together, our results suggest that blood vessel branching is influenced by histamine metabolism, possibly through regulating the expression of the egr-1 transcription factor.

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Chemical enhancer of reg6 mutation. (A) reg6 is a temperature-sensitive mutation and regenerates almost normally at 20°C. Shown is the regenerating vessels 6 days post amputation at 20°C. Note that they regenerated much more slowly at the low temperature. (B) When treated with 300 μM of the histidine decarboxylase inhibitor, urocanic acid, reg6 siblings developed a significant number of swollen vessels (yellow arrows). Red arrows, amputation plane. (C) The enhancement by urocanic acid of reg6 vessel defects was evaluated at two regenerative stages, during anastomosis (3 dpa at 20°C, n = 10) and plexus formation (6 dpa at 20°C, n = 10) that are both affected by the reg6 mutation [16]. U300, 300 μM of urocanic acid.
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Figure 6: Chemical enhancer of reg6 mutation. (A) reg6 is a temperature-sensitive mutation and regenerates almost normally at 20°C. Shown is the regenerating vessels 6 days post amputation at 20°C. Note that they regenerated much more slowly at the low temperature. (B) When treated with 300 μM of the histidine decarboxylase inhibitor, urocanic acid, reg6 siblings developed a significant number of swollen vessels (yellow arrows). Red arrows, amputation plane. (C) The enhancement by urocanic acid of reg6 vessel defects was evaluated at two regenerative stages, during anastomosis (3 dpa at 20°C, n = 10) and plexus formation (6 dpa at 20°C, n = 10) that are both affected by the reg6 mutation [16]. U300, 300 μM of urocanic acid.

Mentions: To further verify the role of histamine in promoting blood vessel branching, we next tested whether blocking histamine synthesis could enhance reg6 vessel branching defects. As stated before, the reg6 mutation is temperature sensitive. At a low temperature (20°C), the number of swollen vessels in reg6 regenerates was nearly zero (Figure 6). We treated reg6 regenerating vessels at this temperature with urocanic acid, one of the inhibitors of histidine decarboxylase which is the key enzyme for histamine synthesis. The results showed that the number of swollen vessels in 3-dpa reg6 regenerating fins at 20°C was about 1.9 ± 1.5/fin (n = 10), and this increased to 6.9 ± 2.9/fin (n = 9) with 300 μM urocanic acid (Figure 6A and 6B for morphological comparisons and C for quantitative data). A similar effect was also observed at 6 dpa during plexus formation of regeneration at 20°C (Figure 6C). Note that fin regeneration was much slower at 20°C than at 33°C, and regeneration at 3 and 6 dpa at 20°C corresponded to the vessel anastomosis and plexus formation stages of vessel regeneration, respectively, both of which are affected by the reg6 mutation [16]. Urocanic acid at 300 μM caused no reg6-like phenotype or toxicity in wild-type adult fish (data not shown).


Histamine metabolism influences blood vessel branching in zebrafish reg6 mutants.

Huang CC, Huang CW, Cheng YS, Yu J - BMC Dev. Biol. (2008)

Chemical enhancer of reg6 mutation. (A) reg6 is a temperature-sensitive mutation and regenerates almost normally at 20°C. Shown is the regenerating vessels 6 days post amputation at 20°C. Note that they regenerated much more slowly at the low temperature. (B) When treated with 300 μM of the histidine decarboxylase inhibitor, urocanic acid, reg6 siblings developed a significant number of swollen vessels (yellow arrows). Red arrows, amputation plane. (C) The enhancement by urocanic acid of reg6 vessel defects was evaluated at two regenerative stages, during anastomosis (3 dpa at 20°C, n = 10) and plexus formation (6 dpa at 20°C, n = 10) that are both affected by the reg6 mutation [16]. U300, 300 μM of urocanic acid.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2291033&req=5

Figure 6: Chemical enhancer of reg6 mutation. (A) reg6 is a temperature-sensitive mutation and regenerates almost normally at 20°C. Shown is the regenerating vessels 6 days post amputation at 20°C. Note that they regenerated much more slowly at the low temperature. (B) When treated with 300 μM of the histidine decarboxylase inhibitor, urocanic acid, reg6 siblings developed a significant number of swollen vessels (yellow arrows). Red arrows, amputation plane. (C) The enhancement by urocanic acid of reg6 vessel defects was evaluated at two regenerative stages, during anastomosis (3 dpa at 20°C, n = 10) and plexus formation (6 dpa at 20°C, n = 10) that are both affected by the reg6 mutation [16]. U300, 300 μM of urocanic acid.
Mentions: To further verify the role of histamine in promoting blood vessel branching, we next tested whether blocking histamine synthesis could enhance reg6 vessel branching defects. As stated before, the reg6 mutation is temperature sensitive. At a low temperature (20°C), the number of swollen vessels in reg6 regenerates was nearly zero (Figure 6). We treated reg6 regenerating vessels at this temperature with urocanic acid, one of the inhibitors of histidine decarboxylase which is the key enzyme for histamine synthesis. The results showed that the number of swollen vessels in 3-dpa reg6 regenerating fins at 20°C was about 1.9 ± 1.5/fin (n = 10), and this increased to 6.9 ± 2.9/fin (n = 9) with 300 μM urocanic acid (Figure 6A and 6B for morphological comparisons and C for quantitative data). A similar effect was also observed at 6 dpa during plexus formation of regeneration at 20°C (Figure 6C). Note that fin regeneration was much slower at 20°C than at 33°C, and regeneration at 3 and 6 dpa at 20°C corresponded to the vessel anastomosis and plexus formation stages of vessel regeneration, respectively, both of which are affected by the reg6 mutation [16]. Urocanic acid at 300 μM caused no reg6-like phenotype or toxicity in wild-type adult fish (data not shown).

Bottom Line: Interestingly, when reg6 adults that had already developed swollen vessel lumina in regenerating fins were treated with histamine or SKF91488, either treatment significantly reduced the number of swollen vessels within 12 h, suggesting a rapid and constant influence of histamine on blood vessel branching.Finally, we identified that the transcription factor, egr-1 (early growth response factor 1), was closely associated with the reg6 phenotype and chemical treatments.Taken together, our results suggest that blood vessel branching is influenced by histamine metabolism, possibly through regulating the expression of the egr-1 transcription factor.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. huangcc@gate.sinica.edu.tw

ABSTRACT

Background: Vascular branching morphogenesis is responsible for the extension of blood vessels into growing tissues, a process crucial for organogenesis. However, the genetic mechanism for vessel branching is largely unknown. Zebrafish reg6 is a temperature-sensitive mutation exhibiting defects in blood vessel branching which results in the formation of swollen vessel lumina during capillary plexus formation.

Results: We performed a screening for chemical suppressors of reg6 and identified SKF91488, an inhibitor of histamine methyltransferase (HMT), that can rescue the reg6 vessel branching defects in a dose-dependent manner. Inhibition of HMT by SKF91488 presumably blocks histamine degradation, thus causing histamine accumulation. Consistent with this idea, we found that a high level of histamine also showed significant suppression of reg6 vessel phenotypes. Interestingly, when reg6 adults that had already developed swollen vessel lumina in regenerating fins were treated with histamine or SKF91488, either treatment significantly reduced the number of swollen vessels within 12 h, suggesting a rapid and constant influence of histamine on blood vessel branching. Furthermore, the expression of HMT was significantly elevated in reg6 regenerating fins. Conversely, lowering histamine by administering urocanic acid, a histidine decarboxylase inhibitor, enhanced the reg6 phenotypes. Finally, we identified that the transcription factor, egr-1 (early growth response factor 1), was closely associated with the reg6 phenotype and chemical treatments.

Conclusion: Taken together, our results suggest that blood vessel branching is influenced by histamine metabolism, possibly through regulating the expression of the egr-1 transcription factor.

Show MeSH
Related in: MedlinePlus