Vasopressin Amplifies the Production of Proinflammatory Mediators in Traumatic Brain Injury

Abstract

Arginine vasopressin (AVP) has previously been shown to promote disruption of the blood-brain barrier, exacerbate edema, and augment the loss of neural tissue in various forms and models of brain injury. However, the mechanisms underlying these AVP actions are not well understood. These mechanisms were studied in AVP-deficient Brattleboro rats (Avp(di/di)), and their parental Long-Evans strain, using a controlled cortical impact model of traumatic brain injury (TBI). The increased influx of inflammatory cells into the injured cortex in wild-type versus Avp(di/di) rats was associated with higher levels of cortical synthesis of the CXC and CC chemokines found in wild-type versus Avp(di/di) rats. These chemokines were predominantly produced by the cerebrovascular endothelium and astrocytes. In astrocyte and brain endothelial cell cultures, AVP acted synergistically with tumor necrosis factor-alpha (TNF-alpha) to increase the TNF-alpha-dependent production of CXC and CC chemokines. These AVP actions were mediated by c-Jun N-terminal kinase (JNK), as shown by Western blotting and pharmacological inhibition of JNK activity. The activity of JNK was increased in response to injury, and the differences in the magnitude of its post-traumatic activation between Avp(di/di) and wild-type rats were observed. These data demonstrate that AVP plays an important role in exacerbating the brain inflammatory response to injury.

Posttraumatic Invasion of Monocytes across the Blood—Cerebrospinal Fluid Barrier

“…Real-time polymerase chain reaction (PCR) was performed as previously described (Szmydynger-Chodobska et al, 2009, 2010. Cyclophilin A was used for the normalization of the data obtained.…”

“…Immunoblotting procedures were performed as previously described (Szmydynger-Chodobska et al, 2010). In brief, proteins were resolved via sodium dodecyl sulfatepolyacrylamide gel electrophoresis (4% to 12%) under reducing conditions and proteins were transferred onto 0.2 mm nitrocellulose membranes (Invitrogen).…”

“…Similarly, invading monocytes have been reported to substantially contribute to the formation of cerebral edema and loss of neural tissue, and to have an adverse effect on neurologic outcome in rodent models of stroke and TBI (Chen et al, 2003;Dimitrijevic et al, 2007;Semple et al, 2010a). Using the Brattleboro rats deficient in vasopressin, a neuropeptide found to substantially augment the posttraumatic synthesis of proinflammatory mediators, we have recently demonstrated that there is an association between the cortical production of neutrophil and monocyte chemoattractants, the magnitude of influx of inflammatory cells, and the extent of loss of neural tissue occurring after TBI (Szmydynger-Chodobska et al, 2010). These results are consistent with previous observations that treatments directed to counter the influx of inflammatory cells into the injured brain are therapeutically beneficial (Beech et al, 2001;Yamasaki et al, 1997).…”

Multiple Sites of Vasopressin Synthesis in the Injured Brain

“…Real-time reverse-transcriptase-PCR was performed as described previously (Szmydynger-Chodobska et al, 2010). Cyclophilin A was used for the normalization of the data obtained.…”

“…Immunohistochemical procedures were performed as described previously (Szmydynger-Chodobska et al, 2010). The following primary antibodies were used: rabbit polyclonal anti-AVP antibody (diluted 1:2,000) from ImmunoStar (Hudson, WI, USA) and mouse monoclonal anti-rat CD11b (clone MRC OX-42; 1 mg/mL) and anti-RECA-1 (clone HIS52; 5 mg/mL) antibodies from Serotec (Oxford, UK).…”