Changes in Pituitary Adenylate Cyclase-Activating Polypeptide Following Renal Ischemia-Reperfusion in Rats

PACAP deficiency as a model of aging

Dysregulation of neuropeptides may play an important role in aging-induced impairments. In the long list of neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) represents a highly effective cytoprotective peptide that provides an endogenous control against a variety of tissue-damaging stimuli. PACAP has neuro- and general cytoprotective effects due to anti-apoptotic, anti-inflammatory, and antioxidant actions. As PACAP is also a part of the endogenous protective machinery, it can be hypothesized that the decreased protective effects in lack of endogenous PACAP would accelerate age-related degeneration and PACAP knockout mice would display age-related degenerative signs earlier. Recent results support this hypothesis showing that PACAP deficiency mimics aspects of age-related pathophysiological changes including increased neuronal vulnerability and systemic degeneration accompanied by increased apoptosis, oxidative stress, and inflammation. Decrease in PACAP expression has been shown in different species from invertebrates to humans. PACAP-deficient mice display numerous pathological alterations mimicking early aging, such as retinal changes, corneal keratinization and blurring, and systemic amyloidosis. In the present review, we summarize these findings and propose that PACAP deficiency could be a good model of premature aging.

The change of plasma pituitary adenylate cyclase-activating polypeptide levels after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Elevated circulating pituitary adenylate cyclase-activating polypeptide (PACAP) levels have been demonstrated to be associated with clinical outcomes of severe traumatic brain injury. The current study aimed to confirm whether elevated plasma PACAP levels are predictive of clinical outcomes of aneurysmal subarachnoid hemorrhage (aSAH).

MATERIALS AND METHODS

One hundred and eighteen aSAH patients and 118 controls were recruited. Plasma PACAP concentrations were determined using enzyme-linked immunosorbent assay. Patients were followed up until death or completion of 6 months after aSAH. An unfavorable outcome was defined as Glasgow Outcome Scale score of 1-3.

RESULTS

The admission PACAP levels were significantly elevated in all patients (296.6 ± 119.7 pg/ml) compared with controls (77.1 ± 17.9 pg/ml, P < 0.001). Plasma PACAP levels were independently associated with clinical severity indicated by World Federation of Neurological Surgeons (WFNS) score (t = 4.745, P < 0.001) and Fisher score (t = 4.239, P < 0.001) using a multivariate linear regression. PACAP was identified as an independent predictor for 6-month mortality [odds ratio (OR), 1.014; 95% confidence interval (CI), 1.005-1.030; P < 0.001] and 6-month unfavorable outcome (OR, 1.012; 95% CI, 1.006-1.028; P < 0.001) and 6-month overall survival (hazard ratio, 1.016; 95% CI, 1.008-1.023; P < 0.001) using a binary logistic regression analysis and a Cox's proportional hazard analysis, respectively. PACAP had similar predictive values compared with WFNS score and Fisher score according to the receiver operating characteristic curve analysis.

CONCLUSIONS

Higher plasma PACAP levels are associated with clinical severity and long-term prognosis of aSAH patients, and PACAP has potential to be a good prognostic biomarker of aSAH.

Distribution and Function of PACAP and Its Receptors in the Healthy and Nephrotic Kidney

BACKGROUND/AIMS

Plasma deficiency of pituitary adenylate cyclase-activating polypeptide (PACAP) was recently demonstrated in children with nephrotic syndrome (NS). Previous studies have reported an important protective effect of PACAP on kidney proximal tubules. The aim of this study was to explore the expression of PACAP and its receptors PAC1, VPAC1 and VPAC2 in the healthy and nephrotic kidney and to determine if PACAP has an effect on renal proximal tubular cells exposed to albumin.

METHODS

Expression of PACAP and its receptors was studied using kidney tissue from healthy and nephrotic children, and in 3 human renal cell lines (glomerular microvascular endothelial cells, podocytes and proximal tubular epithelial HK-2 cells). The functionality of the VPAC1 receptor was tested in HK-2 cells, measuring cyclic adenosine monophosphate levels after PACAP exposure. The influence of PACAP on cell viability and transforming growth factor-β1 (TGF-β1) expression was measured in HK-2 cells exposed to albumin, mimicking proteinuria related damage.

RESULTS

VPAC1 expression was detected in the tubular proximal epithelial cells and in the glomerular podocytes of renal tissue from healthy and nephrotic children. Increased staining for PACAP was found in the proximal tubules of renal sections from children with NS compared to healthy renal sections. Expression and functionality of VPAC1 were demonstrated in HK-2 cells. Finally, PACAP did not alter cell viability or TGF-β1 expression of HK-2 cells exposed to albumin.

CONCLUSION

VPAC1 is the predominant receptor in the human kidney. The enhanced presence of PACAP in proximal tubular epithelial cells in nephrotic kidneys points to the reabsorption of filtered PACAP. On short term, PACAP has no in vitro effect on cell viability and TGF-β1 expression of proximal tubular epithelial cells exposed to high concentrations of albumin.

The effects of pituitary adenylate cyclase activating polypeptide in renal ischemia/reperfusion

Pituitary adenylate cyclase activating polypeptide (PACAP ) is a multifunctional neuropeptide occurring in the nervous system as well as in the peripheral organs. Beneficial action of PACAP has been shown in different pathological processes. The strong protective effects of the peptide are probably due to its complex modulatory actions in antiapoptotic, anti-inflammatory and antioxidant pathways. In the kidney, PACAP is protective in models of diabetic nephropathy, myeloma kidney injury, cisplatin-, gentamycin- and cyclosporin-induced damages. Numerous studies have been published describing the protective effect of this peptide in renal ischemia/reperfusion. The present review focuses on the ischemia/reperfusion-induced kidney injury and gives a brief summary about the results published in this area.

Plasma pituitary adenylate cyclase-activating polypeptide concentrations and mortality after acute spontaneous basal ganglia hemorrhage

BACKGROUND

Plasma pituitary adenylate cyclase activating polypeptide (PACAP) concentrations are elevated after traumatic brain injury. We assessed the prognostic value of PACAP for short-term and long-term mortality of acute intracerebral hemorrhage (ICH) patients.

METHODS

A total of 150 patients and 150 age- and gender- matched healthy controls were recruited. The plasma PACAP concentrations were measured using sandwich immunoassays. ICH severity was assessed using hematoma volume and National Institutes of Health Stroke Scale (NIHSS) score. The end points included 1-week mortality and 6-month mortality. The relationships between plasma PACAP concentrations and ICH severity and the end points were analyzed statistically.

RESULTS

Plasma PACAP concentrations were statistically significantly higher in the ICH patients than in the healthy controls and were correlated positively with hematoma volumes and NIHSS scores using a multivariate linear regression. Multivariate analysis results indicated that plasma PACAP concentration was an independent predictor of 1-week mortality, 6-month mortality and 6-month overall survival. It also had high predictive value based on receiver operating characteristic curve.

CONCLUSIONS

Plasma PACAP concentrations are increased and are highly associated with the severity of ICH; PACAP may be a good predictor of short-term and long-term mortality of ICH.

Delayed administration of pituitary adenylate cyclase-activating polypeptide 38 ameliorates renal ischemia/reperfusion injury in mice by modulating Toll-like receptors

We investigated whether pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) ameliorates kidney injury after ischemia/reperfusion (IR) by modulating Toll-like receptor (TLR)-associated signaling pathways. Male C57BL/6 mice were subjected to bilateral renal ischemia for 45 min. PACAP38, 20 μg in 100 μl of saline, was administered i.p. at 24 and 48 h after IR, and mice were euthanized at 72h. In IR mice, PACAP38 maintained serum creatinine near control levels (0.81 ± 0.08 vs. 0.69 ± 0.17 mg/dl in controls, p=NS, vs. 1.8 ± 0.03 in saline-treated IR mice, p<0.01) and significantly reduced the expression of kidney injury biomarkers. PACAP38 significantly reduced the levels of apoptosis and neutrophil infiltration, and protected against tubular damage. With PCR arrays, 59 of 83 TLR-related genes significantly changed their expression after IR. TLR2 increased 162 fold, followed by Fas-associated death domain (37 fold) and TLR6 (24 fold), while ubiquitin-conjugating enzyme E2 variant 1 (UBE2V1) decreased 55 fold. PACAP38 given 24 and 48 h after IR injury significantly reversed these changes in 56 genes, including TLR2, TLR3, TLR4, TLR6, and genes in the NF-κB pathways. The alterations in TLR2, TLR3, TLR6, and UBE2V1 were confirmed by RT-PCR. After IR, PACAP38 also suppressed protein levels of TLR-associated cytokines. PACAP38 reversed the changes in IR-activated TLR-associated NF-κB signaling pathways even when treatment was delayed 24h. Therefore, PACAP38 could be an effective therapeutic for unexpected IR-mediated renal injury. The prominently IR-induced TLR-related genes identified in this study could be novel drug targets.

Effects of pituitary adenylate cyclase activating polypeptide in the urinary system, with special emphasis on its protective effects in the kidney

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widespread neuropeptide with diverse effects in the nervous system and peripheral organs. One of the most well-studied effects of PACAP is its cytoprotective action, against different harmful stimuli in a wide variety of cells and tissues. PACAP occurs in the urinary system, from the kidney to the lower urinary tract. The present review focuses on the nephroprotective effects of PACAP and summarizes data obtained regarding the protective effects of PACAP in different models of kidney pathologies. In vitro data show that PACAP protects tubular cells against oxidative stress, myeloma light chain, cisplatin, cyclosporine-A and hypoxia. In vivo data provide evidence for its protective effects in ischemia/reperfusion, cisplatin, cyclosporine-A, myeloma kidney injury, diabetic nephropathy and gentamicin-induced kidney damage. Results accumulated on the renoprotective effects of PACAP suggest that PACAP is an emerging candidate for treatment of human kidney pathologies.