Complement component C3a or C3a desArg as a new marker for estimation of local vital reactions in incised skin wounds

Mast cells and complement system: Ancient interactions between components of innate immunity

The emergence and evolution of the complement system and mast cells (MCs) can be traced back to sea urchins and the ascidian Styela plicata, respectively. Acting as a cascade of enzymatic reactions, complement is activated through the classical (CP), the alternative (AP), and the lectin pathway (LP) based on the recognized molecules. The system's main biological functions include lysis, opsonization, and recruitment of phagocytes. MCs, beyond their classic role as master cells of allergic reactions, play a role in other settings, as well. Thus, MCs are considered as extrahepatic producers of complement proteins. They express various complement receptors, including those for C3a and C5a. C3a and C5a not only activate the C3aR and C5aR expressing MCs but also act as chemoattractants for MCs derived from different anatomic sites, such as from the bone marrow, human umbilical cord blood, or skin in vitro. Cross talk between MCs and complement is facilitated by the production of complement proteins by MCs and their activation by the MC tryptase. The coordinated activity between MCs and the complement system plays a key role, for example, in a number of allergic, cutaneous, and vascular diseases. At a molecular level, MCs and complement system interactions are based on the production of several complement zymogens by MCs and their activation by MC-released proteases. Additionally, at a cellular level, MCs act as potent effector cells of complement activation by expressing receptors for C3a and C5a through which their chemoattraction and activation are mediated by anaphylatoxins in a paracrine and autocrine fashion.

Cell type specific gene expression profiling reveals a role for complement component C3 in neutrophil responses to tissue damage

Tissue damage induces rapid recruitment of leukocytes and changes in the transcriptional landscape that influence wound healing. However, the cell-type specific transcriptional changes that influence leukocyte function and tissue repair have not been well characterized. Here, we employed translating ribosome affinity purification (TRAP) and RNA sequencing, TRAP-seq, in larval zebrafish to identify genes differentially expressed in neutrophils, macrophages, and epithelial cells in response to wounding. We identified the complement pathway and c3a.1, homologous to the C3 component of human complement, as significantly increased in neutrophils in response to wounds. c3a.1^−/− zebrafish larvae have impaired neutrophil directed migration to tail wounds with an initial lag in recruitment early after wounding. Moreover, c3a.1^−/− zebrafish larvae have impaired recruitment to localized bacterial infections and reduced survival that is, at least in part, neutrophil mediated. Together, our findings support the power of TRAP-seq to identify cell type specific changes in gene expression that influence neutrophil behavior in response to tissue damage.

Activation of the aryl hydrocarbon receptor increases pulmonary neutrophilia and diminishes host resistance to influenza A virus

Unlike their role in bacterial infection, less is known about the role of neutrophils during pulmonary viral infection. Exposure to pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) results in excess neutrophils in the lungs of mice infected with influenza A virus. TCDD is the most potent agonist for the aryl hydrocarbon receptor (AhR), and exposure to AhR ligands has been correlated with exacerbated inflammatory lung diseases. However, knowledge of the effects of AhR agonists on neutrophils is limited. Likewise, the factors regulating neutrophil responses during respiratory viral infections are not well characterized. To address these knowledge gaps, we determined the in vivo levels of KC, MIP-1alpha, MIP-2, LIX, IL-6, and C5a in infected mouse lungs. Our data show that these neutrophil chemoattractants are generally produced transiently in the lung within 12-24 h of infection. We also report that expression of CD11a, CD11b, CD49d, CD31, and CD38 is increased on pulmonary neutrophils in response to influenza virus. Using AhR-deficient mice, we demonstrate that excess neutrophilia in the lung is mediated by activation of the AhR and that this enhanced neutrophilia correlates directly with decreased survival in TCDD-exposed mice. Although AhR activation results in more neutrophils in the lungs, we show that this is not mediated by deregulation in levels of common neutrophil chemoattractants, expression of adhesion molecules on pulmonary neutrophils, or delayed death of neutrophils. Likewise, exposure to TCDD did not enhance pulmonary neutrophil function. This study provides an important first step in elucidating the mechanisms by which AhR agonists exacerbate pulmonary inflammatory responses.

Trimellitic anhydride-induced cellular infiltration into Guinea pig lung varies with age but not gender

BACKGROUND

In humans the incidence of asthma changes with age and gender. Immature guinea pigs have been used to model the allergic response to the occupational allergen trimellitic anhydride (TMA) where exposure to adults is paramount. We hypothesized that the TMA-induced allergic response in immature guinea pigs was similar to mature animals, regardless of gender.

METHODS

Sexually immature and mature female and male guinea pigs were sensitized intradermally with TMA. Three weeks after sensitization they were challenged intratracheally with TMA conjugated to guinea pig serum albumin (TMA-GPSA) or GPSA as a control. Twenty-four hours later cell infiltration into the lung was determined. TMA-specific IgG(1) and IgG(2) were measured in plasma and the complement activation product C3a was measured in the bronchoalveolar lavage fluid.

RESULTS

In control animals, numbers of eosinophils and neutrophils varied with age and gender. The TMA-GPSA- induced cellular infiltration was similar in all age/gender groups. However, neutrophils in the lung tissue increased only in immature animals. IgG antibodies differed between groups but did not account for differences in cell infiltration. C3a correlated with the extent of cell infiltration in all groups except mature females.

CONCLUSIONS

TMA-induced neutrophilia differs with age. TMA-induced changes in eosinophils and macrophages did not vary with age or gender. The relationship between complement activation and inflammation in mature females differs from that in the other groups, suggesting mediators of the response may change with age and gender. Effects of age and gender need to be considered in animal models of the allergic response.

Advances in the diagnosis of wound vitality: a review

The diagnosis of the vital origin of wounds in many cases remains an unsolved problem for the forensic pathologist. Practical experience enables the expert to diagnose the vital or postmortem origin of wounds on the basis of macroscopic examination. In some cases, optic microscopy is used to confirm the diagnosis. In many other cases, additional more sensitive and specific markers of vitality are required. In the past 50 years, comprehensive research on this topic has resulted in a better understanding of the acute inflammatory reaction. The development and application of sensitive and specific markers through research in the areas of histochemistry, enzymology, and biochemistry has provided a partial solution to the problems involved in wound vitality diagnosis. A review of this challenging area of forensic pathology, including an explanation of these methods and markers, is presented in this paper.

Minor role of the C3a receptor in systemic anaphylaxis in the guinea pig

Previously, Regal et al. [Regal, J.F., Fraser, D.G., Toth, C.A., 1993. Role of the complement system in antigen-induced bronchoconstriction and changes in blood pressure in the guinea pig. J. Pharmacol. Exp. Ther. 267, 979-988] demonstrated that preventing complement system activation resulted in inhibition of anaphylaxis in the guinea pig, and that the C-terminal 21 amino acids of guinea pig C3a (C3a-peptide) mimic the symptoms of anaphylactic shock in the guinea pig [Regal, J.F., 1997. Role of the complement system in pulmonary disorders. Immunopharmacology 38, 17-25]. To determine if C3a is an essential mediator of systemic anaphylaxis, the anaphylactic response to ovalbumin (OA) was assessed in guinea pigs genetically deficient in the C3a receptor (C3aR-) compared to their control strain of animals which were C3a receptor positive (C3aR+). In addition, the response to another control strain of animals, Hartley guinea pigs, was determined. Sensitized guinea pigs were anesthetized, and bronchoconstriction and changes in blood pressure were monitored in response to intravenous (i.v.) injection of either C3a-peptide, recombinant human C5a (rHuC5a) or OA. Both Hartley guinea pigs and C3aR+ animals responded similarly to C3a-peptide and rHuC5a. C3aR- animals, however, were unresponsive to C3a-peptide and responded normally to rHuC5a, confirming their functional deficiency of the C3a receptor. In response to OA, C3aR+ animals and Hartley guinea pigs responded with a severe bronchoconstriction, an initial transient hypotension, followed by an increase in blood pressure and a delayed prolonged hypotensive response. In contrast, in C3aR- animals, the increased blood pressure response to OA was significantly prolonged, the delayed hypotensive response was blunted, and the bronchoconstriction was delayed compared to the C3aR+ animals. The difference in the anaphylactic response could not be explained by differing amounts of OA-specific IgG1 antibody or C3a generated during the anaphylactic response. Thus, these data suggest that C3a plays a minor role in the hypotension of systemic anaphylaxis and investigation of a role for other products of complement system activation, either alone or in combination with C3a, is clearly warranted.

Estimation of local vital reactions in severely burned tissues of guinea pig skin using C3a or C3a desArg as a marker

We observed changes in levels of anaphylatoxin C3a and/or its desArg (C3a/C3a desArg) peptides in the local site of severely burned skin tissues of guinea pigs using immuno-Western blotting methods. The C3a/C3a desArg peptides, which were probably generated during complement activation, were detected at significant levels from 30 min to 72 h following burn injury in an area limited to 3 mm from the wound edge. Levels of these peptides showed a tendency to be highest in that area 24 h after burn infliction. In postmortem injuries, C3a/C3a desArg peptides could not be detected. These peptides were detected in antemortem wounds up to at least 2 days at 22 degrees C and up to 3 days at 4 degrees C after death, although decreases in levels were found. Lower concentrations of these peptides were also found in postmortem burns in which postmortem hypostasis appeared strongly. These results suggest that, except for injuries of the area with obvious postmortem hypostasis, detection of C3a/C3a desArg can be useful for estimation of vital reactions in many kinds of wounds during inflammation.