VIP and PACAP inhibit Fas ligand-mediated bystander lysis by CD4(+) T cells

Pituitary adenylate cyclase-activating peptide: Potential roles in the pathophysiology and complications of cirrhosis

Pituitary adenylate cyclase-activating peptide (PACAP) is a ubiquitous neuropeptide with diverse functions throughout the organism. Most abundantly investigated for its role in several neurological disorders as well as in circadian rhythms, other fields of medicine, including cardiology, have recently shown interest in the role of PACAP and its potential as a biomarker. Timely diagnosis and treatment of cirrhosis and its complications is a considerable challenge for health services world-wide and development of new areas of research is warranted. Direct and indirect evidence exists of PACAP involvement in the cascade of pathological events and processes ultimately leading to cirrhosis and its complications, but its exact role remains to be determined. Studies have documented PACAP involvement in immune function, metabolism, local vasoconstriction and dilatation and systemic vascular decompensation and there is ongoing research of a possible role in liver reperfusion injury. Considering these reports, PACAP could theoretically exude influence on the disease course of cirrhosis through the hypothalamus-pituitary-adrenal axis, chronic inflammation, fibrogenesis, vasodilation and reduced vascular resistance. The paucity of literature on the specific topic of PACAP and cirrhosis reflects complex mechanisms and difficulty in accurate measurements and sample taking. This does not detract from the need to further characterize and elucidate the role PACAP plays in the underdiagnosed and undertreated condition of cirrhosis.

Correlation of Circulating T Lymphocytes and Intracranial Hypertension in Intracerebral Hemorrhage

BACKGROUND

The close correlation between intracerebral pressure (ICP) and immunologic responses has been well described, but the role of T lymphocytes in this process remains unknown. This study targeted the relationship of circulating T lymphocytes and ICP in patients with intracerebral hemorrhage (ICH).

METHODS

Between October 2015 and October 2016, consecutive patients age 18-65 years with ICH were enrolled. ICP values were recorded hourly for 5 days, and the screened patients were divided into 2 groups based on ICP: the elevated ICP group (ICP >20 mmHg) and normal ICP group (ICP ≤20 mmHg). Peripheral blood was collected on admission and T lymphocyte subpopulations were analyzed by flow cytometry. Glasgow Coma Scale score on admission and Glasgow Outcome Scale (GOS) score at 30 days after ICH were analyzed.

RESULTS

A total of 44 patients were enrolled, including 18 patients in the elevated ICP group and 26 in the normal ICP group. Both CD3⁺ and CD4⁺ T lymphocyte counts were higher in the elevated ICP group (P = 0.004 and 0.000, respectively). The CD8⁺ T lymphocyte count was not significantly different between the 2 groups (P = 0.751). There were correlation trends between the maximum ICP value and CD3⁺ lymphocyte count (P = 0.003), CD4⁺ T lymphocyte count (P = 0.000), and the CD4⁺/CD8⁺ T lymphocyte ratio (P = 0.000). The area under the curve (AUC) of CD4⁺/CD8⁺ T lymphocyte ratio was the largest among them (P = 0.011 and 0.033), with a significant cutoff value and good specificity and sensitivity. There was a close correlation between the CD4⁺/CD8⁺ T lymphocyte ratio and the 30-day GOS score (P = 0.003, AUC = 0.812).

CONCLUSIONS

The CD4⁺/CD8⁺ T lymphocyte ratio may be a valuable indicator for predicting postoperative ICP and the short-term prognosis after ICH.

Effects of pituitary adenylate cyclase activating polypeptide on CD4(+)/CD8(+) T cell levels after traumatic brain injury in a rat model

BACKGROUND

The effect of pituitary adenylate cyclase activating polypeptide (PACAP) during traumatic brain injury (TBI) and whether it can modulate secondary injury has not been reported previously. The present study evaluated the potential protective effects of ventricular infusion of PACAP in a rat model of TBI.

METHODS

Male Sprague Dawley rats were randomly divided into 3 treatment groups (n=6, each): sham-operated, vehicle (normal saline)+TBI, and PACAP+TBI. Normal saline or PACAP (1 μg/5 μL) was administered intracerebroventricularly 20 minutes before TBI. Right parietal cortical contusion was produced via a weight-dropping method. Brains were extracted 24 hours after trauma. Histological changes in brains were examined by HE staining. The numbers of CD4(+) and CD8(+) T cells in blood and the spleen were detected via flow cytometry.

RESULTS

In injured brain regions, edema, hemorrhage, inflammatory cell infiltration, and swollen and degenerated neurons were observed under a light microscope, and the neurons were disorderly arrayed in the hippocampi. Compared to the sham group, average CD4(+) CD8(-) lymphocyte counts in blood and the spleen were significantly decreased in rats that received TBI+vehicle, and CD4(-) CD8(+) were increased. In rats administered PACAP prior to TBI, damage was attenuated as evidenced by significantly increased CD4(+), and decreased CD8(+), T lymphocytes in blood and the spleen.

CONCLUSION

Pretreatment with PACAP may protect against TBI by influencing periphery T cellular immune function.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Plasma pituitary adenylate cyclase activating polypeptide (PACAP) levels in chronic hepatitis B patients under lamivudine treatment

OBJECTIVE

Lamivudine is a nucleoside analogue with potent antiviral activity against hepatitis B virus (HBV). Plasma pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide that is produced within the lymphoid microenvironment and induces the production of Th2-type cytokines. The aim of our study was to investigate the possible alterations of plasma PACAP-38 levels in chronic hepatitis B (CHB) patients during lamivudine treatment and to compare them with biochemical, virological and histological data.

METHODS

Plasma PACAP-38 levels were measured using competitive radio-immune analysis (RIA) in 25 CHB patients before and after completion of a 52-week lamivudine treatment period and in 22 healthy blood donors. Biochemical evaluation was done at baseline and every three months during treatment. Virological evaluation (HBV-DNA) was performed at baseline and at weeks 24 and 52 of treatment. Baseline liver histology was assessed for all patients at the beginning and at week 52 of the study for histological comparison with the pretreatment biopsy, according to the Ishak scoring system. Statistical evaluation of data was done using analysis of variance and Student's t-test.

RESULTS

Virological breakthrough was observed in seven (28%) patients at week 52 of treatment. Histological improvement was observed in 21 (84%) CHB patients, despite the emergence of tyrosine-methionine-aspartate-aspartate (YMDD) mutations. Plasma PACAP-38 levels were significantly lower in CHB patients at baseline than in healthy blood donors. Significant elevation of plasma peptide levels was observed in CHB patients after the completion of lamivudine treatment period, even in the subgroup of those who exhibited YMDD variants.

CONCLUSION

The elevation of plasma PACAP-38 levels in treated CHB patients following lamivudine-induced elimination of viraemia suggests a possible alteration of T-cellular immune response, resulting in biochemical and histological remission of liver disease, even in patients who exhibited virological breakthrough.

PACAP in immunity and inflammation

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti-inflammatory factor that exerts its function by regulating the production of both anti- and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) as modulators of both innate and adaptive immunity

The structurally related neuropeptides VIP and PACAP are released within the lymphoid organs following antigenic stimulation, and modulate the function of inflammatory cells through specific receptors. In activated macrophages, VIP and PACAP inhibit the production of pro-inflammatory agents (cytokines, chemokines, and nitric oxide), and stimulate the production of the anti-inflammatory cytokine IL-10. These events are mediated through the VIP/PACAP effects on de novo expression or nuclear translocation of several transcription factors, i.e., NFkappaB, CREB, c-Jun, JunB, and IRF-1. The in vivo administration of VIP/PACAP results in a similar pattern of cytokine and chemokine modulation, which presumably mediates the protective effect of VIP/PACAP in septic shock. In addition, VIP/PACAP reduce the expression of the co-stimulatory molecules B7.1/B7.2, and the subsequent stimulatory activity of macrophages for T-helper cells. In T-cells expressing specific VIP/PACAP receptors, VIP and PACAP inhibit the expression of FasL through effects on NFkappaB, NFAT, and Egr2/3. The reduction of FasL expression has several biological consequences: inhibition of antigen-induced cell death in CD4 T-cells, inhibition of the FasL-mediated cytotoxicity of CD8 and CD4 effectors against direct and bystander targets, and promotion of long-term memory Th2 cells, through a positive effect on the survival of Th2, but not Th1, effectors. The various biological effects of VIP and PACAP are discussed within the range of a general anti-inflammatory model.