Impaired D-myo-inositol 1,4,5-triphosphate generation from cord blood polymorphonuclear leukocytes.
D-myo-Inositol 1,4,5-triphosphate (IP3) is a key second messenger in many cells, including macrophages, T and B cells, and neutrophils, in which it regulates free intracellular calcium ion levels. In human polymorphonuclear leukocytes the rise of intracellular [Ca2+] is the signal that activates a number of functions such as adherence, aggregation, chemotaxis, and degranulation, which are typically depressed in newborn infants. IP3 generation can be stimulated by N-formyl-methionyl-leucylphenylalanine (fMLP) tripeptide, which mimics the naturally occurring bacterial oligopeptides. In this study both neonatal and adult polymorphonuclear leukocytes were stimulated by fMLP (1 x 10(-6) M) and the levels of IP3 were assayed by a specific radiometric method. The time course of IP3 generation was studied for up to 60 s in a total of 10 samples. The response appeared reduced in cord blood samples. To confirm this observation, we extended our study to a larger number of samples, quantitating [IP3] at the time peak of 10 s. As expected IP3 generation was significantly (F test, p < 0.0001, n = 39) lower in newborns than in adults (means +/- SD = 0.64 +/- 0.25; 1.26 +/- 0.36, ng/10(6) cells, respectively). Besides soluble stimulus, neutrophils were treated with a particulate stimulus, namely serum-treated zymosan, which is also able to stimulate IP3 synthesis from polymorphonuclear leukocytes. Serum-treated zymosan produced a prolonged elevation in the level of IP3, reaching a plateau within 120 s in both cord blood and in control samples.(ABSTRACT TRUNCATED AT 250 WORDS)
Santoro
P
P
Department of Pediatrics, University Federico II, Naples, Italy.
Agosti
V
V
Viggiano
D
D
Palumbo
A
A
Sarno
T
T
Ciccimarra
F
F
D000328:Adult; D000595:Amino Acid Sequence; D002118:Calcium / Q000097:blood; D005312:Fetal Blood / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D015544:Inositol 1,4,5-Trisphosphate / Q000097:blood*; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000737:chemistry / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D015054:Zymosan / Q000494:pharmacology
D009240:N-Formylmethionine Leucyl-Phenylalanine; D015544:Inositol 1,4,5-Trisphosphate; D015054:Zymosan; D002118:Calcium