12433
Exposure of human bronchial epithelial cells to an organic extract of diesel exhaust particle was followed by TRPV4 mediating Ca ( + + ) influx , increased RAS expression , mitogen - activated protein kinase signaling , and matrix metalloproteinase - 1 activation .
 Ca ( + + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Ca ( + + )