Background & Aims

Sickle cell disease (SCD) is a hereditary hemoglobinopathy with high prevalence and mortality rate. Patients with SCD have atypical hemoglobin called hemoglobin S (HbS), which gives red blood cells (RBC) their sickle shape. When sickled RBC, which are rigid and inflexible, stick to small blood vessels, severe painful vaso-occlusive episodes (VOE) occur that often result in hospitalization. Despite the severity of the problem, the mechanisms of acute painful VOE in SCD have not been sufficiently studied, which limits the effectiveness and safety of treatments. We previously reported that exposure to cold caused mechanical, thermal, and deep tissue hyperalgesia in non-hyperalgesic mice with SCD (1). The appearance of hyperalgesia in HbSS mice was accompanied by an increase in heart rate, microvascular stasis and hypoxemia. Here we tested whether exposure to cold causes spontaneous nocifensive behavior in HbSS mice and assessed the role of lysophosphatidic acid (LPA) signaling.

Methods

The effect of low temperature (10oC, 1h) was tested on humanized Townes transgenic mice expressing human sickle HbS (HbSS) or normal human HbA (HbAA) hemoglobin. Spontaneous nocifensive behaviors were assessed by the parameters of grimaces and body posture that were videotaped before and after exposure to cold. Mechanical hyperalgesia was defined as a decrease in paw withdrawal threshold determined for each hind paw using calibrated von Frey monofilaments. Heat hyperalgesia was defined as a decrease in paw withdrawal latency in response to a radiant heat stimulus applied to the plantar hind paw. A reference color palette was used to evaluate hemolysis. Sickled RBC were counted in blood smears. The total LPA level was measured in plasma using a commercial kit. The functional contribution of LPA-LPA1 signaling to painful VOE was tested with an LPA1 receptor antagonist, AM966, or with LPA1 receptor siRNA.

Results

In steady-state, neither control HbAA mice nor non-hyperalgesic or hyperalgesic HbSS mice showed spontaneous nocifensive behavior. Exposure to cold caused the appearance of spontaneous nocifensive behavior in all groups of HbSS mice, which was accompanied by increased RBC sickling, hemolysis and increased plasma level of LPA. Cold exposure caused no changes in HbAA mice. Both LPA1 receptor antagonist and LPA1 receptor siRNA treatments effectively attenuated hyperalgesia and cold-induced spontaneous nocifensive behavior, indicating that LPA-LPA1 signaling contributes to painful VOE.

Conclusions

The clinically significant model of cold-induced painful VOE that we have developed allowed us to identify the LPA-LPA1 axis as one of the key mechanism underlying spontaneous nocifensive behaviors in SCD.

References

1. Khasabova I, Juliette J, Rogness VM, Khasabov SG, Golovko MY, Golovko SA, Kiven S, Gupta K, Belcher JD, Vercellotti GM, Seybold VS, Simone DA. A model of painful vaso-occlusive crisis in mice with sickle cell disease. Blood. 2022 Oct 20;140(16):1826-1830. doi: 10.1182/blood.2022017309. PMID: 35960856; PMCID: PMC9837430.

Presenting Author

Iryna Khasabova

Poster Authors

Iryna Khasabova

PhD

University of Minnesota

Lead Author

E-mail

Viacheslav Viatchenko-Karpinski

UMN

Lead Author

E-mail

Ana Alves BS

University of Minnesota

Lead Author

E-mail

Malcolm Johns

UMN

Lead Author

E-mail

Annabelle Herold

UMN

Lead Author

E-mail

Sergey Khasabov

University of Minnesota

Lead Author

E-mail

Donald A. Simone Ph.D.

UMN

Lead Author

E-mail

Topics

  • Models: Acute Pain